feat(misc): set a development conditional export for buildable libraries when using the ts solution setup (#30451)

Update library generators to set a `development` conditional export for
buildable libraries' `package.json` files and set the
`customConditions` compiler options in `tsconfig.base.json`. This will
only be done for workspaces using the TS solution setup.

## Current Behavior

## Expected Behavior

## Related Issue(s)

Fixes #

packages/esbuild/src/generators/configuration/configuration.ts

@@ -167,6 +167,9 @@ function updatePackageJson(
       esbuildOptions,
     } = mergedTarget.options;
 
+    // the file must exist in the TS solution setup
+    const tsconfigBase = readJson(tree, 'tsconfig.base.json');
+
     // can't use the declarationRootDir as rootDir because it only affects the typings,
     // not the runtime entry point
     packageJson = getUpdatedPackageJsonContent(packageJson, {
@@ -186,6 +189,10 @@ function updatePackageJson(
       outputFileExtensionForEsm: getOutExtension('esm', {
         userDefinedBuildOptions: esbuildOptions,
       }),
+      skipDevelopmentExports:
+        !tsconfigBase.compilerOptions?.customConditions?.includes(
+          'development'
+        ),
     });
 
     if (declarationRootDir !== dirname(main)) {

packages/expo/src/generators/library/library.spec.ts

@@ -467,6 +467,7 @@ describe('lib', () => {
         compilerOptions: {
           composite: true,
           declaration: true,
+          customConditions: ['development'],
         },
       });
       writeJson(appTree, 'tsconfig.json', {
@@ -630,13 +631,14 @@ describe('lib', () => {
         {
           "exports": {
             ".": {
-              "default": "./src/index.ts",
+              "default": "./dist/index.cjs.js",
-              "import": "./src/index.ts",
+              "development": "./src/index.ts",
+              "import": "./dist/index.esm.js",
               "types": "./dist/index.esm.d.ts",
             },
             "./package.json": "./package.json",
           },
-          "main": "./src/index.ts",
+          "main": "./dist/index.cjs.js",
           "module": "./dist/index.esm.js",
           "name": "@proj/my-lib",
           "peerDependencies": {
@@ -649,6 +651,25 @@ describe('lib', () => {
       `);
     });
 
+    it('should not set the "development" condition in exports when it does not exist in tsconfig.base.json', async () => {
+      updateJson(appTree, 'tsconfig.base.json', (json) => {
+        delete json.compilerOptions.customConditions;
+        return json;
+      });
+
+      await expoLibraryGenerator(appTree, {
+        ...defaultSchema,
+        buildable: true,
+        strict: false,
+        useProjectJson: false,
+        skipFormat: true,
+      });
+
+      expect(
+        readJson(appTree, 'my-lib/package.json').exports['.']
+      ).not.toHaveProperty('development');
+    });
+
     it('should set "nx.name" in package.json when the user provides a name that is different than the package name', async () => {
       await expoLibraryGenerator(appTree, {
         ...defaultSchema,

packages/expo/src/generators/library/library.ts

@@ -295,6 +295,15 @@ function createFiles(host: Tree, options: NormalizedSchema) {
 function determineEntryFields(
   options: NormalizedSchema
 ): Pick<PackageJson, 'main' | 'types' | 'exports'> {
+  if (
+    options.buildable ||
+    options.publishable ||
+    !options.isUsingTsSolutionConfig
+  ) {
+    // For buildable libraries, the entries are configured by the bundler (i.e. Rollup).
+    return undefined;
+  }
+
   return {
     main: options.js ? './src/index.js' : './src/index.ts',
     types: options.js ? './src/index.js' : './src/index.ts',

packages/js/src/generators/init/files/ts-solution/tsconfig.base.json__tmpl__

@@ -17,6 +17,7 @@
     "noUnusedLocals": true,
     "skipLibCheck": true,
     "strict": true,
-    "target": "es2022"
+    "target": "es2022",
+    "customConditions": ["development"]
   }
 }

packages/js/src/generators/init/init.spec.ts

@@ -208,7 +208,8 @@ describe('js init generator', () => {
           "noUnusedLocals": true,
           "skipLibCheck": true,
           "strict": true,
-          "target": "es2022"
+          "target": "es2022",
+          "customConditions": ["development"]
         }
       }
       "

packages/js/src/generators/library/library.spec.ts

@@ -1817,6 +1817,7 @@ describe('lib', () => {
         compilerOptions: {
           composite: true,
           declaration: true,
+          customConditions: ['development'],
         },
       });
       writeJson(tree, 'tsconfig.json', {
@@ -1954,6 +1955,7 @@ describe('lib', () => {
           "exports": {
             ".": {
               "default": "./dist/index.js",
+              "development": "./src/index.ts",
               "import": "./dist/index.js",
               "types": "./dist/index.d.ts",
             },
@@ -1987,6 +1989,7 @@ describe('lib', () => {
           "exports": {
             ".": {
               "default": "./dist/index.js",
+              "development": "./src/index.ts",
               "import": "./dist/index.js",
               "types": "./dist/index.d.ts",
             },
@@ -2428,5 +2431,26 @@ describe('lib', () => {
       expect(readJson(tree, 'my-lib/project.json').name).toBe('my-lib');
       expect(readJson(tree, 'my-lib/package.json').nx).toBeUndefined();
     });
+
+    it('should not set the "development" condition in exports when it does not exist in tsconfig.base.json', async () => {
+      updateJson(tree, 'tsconfig.base.json', (json) => {
+        delete json.compilerOptions.customConditions;
+        return json;
+      });
+
+      await libraryGenerator(tree, {
+        ...defaultOptions,
+        directory: 'my-lib',
+        name: 'my-lib',
+        useProjectJson: true,
+        bundler: 'tsc',
+        addPlugin: true,
+        skipFormat: true,
+      });
+
+      expect(
+        readJson(tree, 'my-lib/package.json').exports['.']
+      ).not.toHaveProperty('development');
+    });
   });
 });

packages/js/src/generators/library/library.ts

@@ -10,6 +10,7 @@ import {
   names,
   offsetFromRoot,
   ProjectConfiguration,
+  readJson,
   readNxJson,
   readProjectConfiguration,
   runTasksInSerial,
@@ -631,6 +632,9 @@ function createFiles(tree: Tree, options: NormalizedLibraryGeneratorOptions) {
         options.isUsingTsSolutionConfig &&
         !['none', 'rollup', 'vite'].includes(options.bundler)
       ) {
+        // the file must exist in the TS solution setup
+        const tsconfigBase = readJson(tree, 'tsconfig.base.json');
+
         return getUpdatedPackageJsonContent(updatedPackageJson, {
           main: join(options.projectRoot, 'src/index.ts'),
           outputPath: joinPathFragments(options.projectRoot, 'dist'),
@@ -639,6 +643,10 @@ function createFiles(tree: Tree, options: NormalizedLibraryGeneratorOptions) {
           generateExportsField: true,
           packageJsonPath,
           format: ['esm'],
+          skipDevelopmentExports:
+            !tsconfigBase.compilerOptions?.customConditions?.includes(
+              'development'
+            ),
         });
       }
 
@@ -664,6 +672,8 @@ function createFiles(tree: Tree, options: NormalizedLibraryGeneratorOptions) {
       options.isUsingTsSolutionConfig &&
       !['none', 'rollup', 'vite'].includes(options.bundler)
     ) {
+      const tsconfigBase = readJson(tree, 'tsconfig.base.json');
+
       packageJson = getUpdatedPackageJsonContent(packageJson, {
         main: join(options.projectRoot, 'src/index.ts'),
         outputPath: joinPathFragments(options.projectRoot, 'dist'),
@@ -672,6 +682,10 @@ function createFiles(tree: Tree, options: NormalizedLibraryGeneratorOptions) {
         generateExportsField: true,
         packageJsonPath,
         format: ['esm'],
+        skipDevelopmentExports:
+          !tsconfigBase.compilerOptions?.customConditions?.includes(
+            'development'
+          ),
       });
     }
 

packages/js/src/generators/setup-build/generator.ts

@@ -325,6 +325,11 @@ function updatePackageJson(
       version: '0.0.1',
     };
   }
+
+  // the file must exist in the TS solution setup, which is the only case this
+  // function is called
+  const tsconfigBase = readJson(tree, 'tsconfig.base.json');
+
   packageJson = getUpdatedPackageJsonContent(packageJson, {
     main,
     outputPath,
@@ -333,6 +338,8 @@ function updatePackageJson(
     packageJsonPath,
     rootDir,
     format,
+    skipDevelopmentExports:
+      !tsconfigBase.compilerOptions?.customConditions?.includes('development'),
   });
   writeJson(tree, packageJsonPath, packageJson);
 }

packages/js/src/plugins/typescript/plugin.spec.ts

@@ -2206,6 +2206,111 @@ describe(`Plugin: ${PLUGIN_NAME}`, () => {
       `);
     });
 
+    it('should not create build target when the entry points point to source files', async () => {
+      // Sibling package.json
+      await applyFilesToTempFsAndContext(tempFs, context, {
+        'libs/my-lib/tsconfig.json': `{}`,
+        'libs/my-lib/tsconfig.lib.json': `{"compilerOptions": {"outDir": "dist"}}`,
+        'libs/my-lib/package.json': JSON.stringify({
+          exports: {
+            '.': {
+              default: './src/index.ts',
+            },
+          },
+        }),
+      });
+      expect(
+        await invokeCreateNodesOnMatchingFiles(context, {
+          // Reduce noise in build snapshots by disabling default typecheck target
+          typecheck: false,
+          build: true,
+        })
+      ).toMatchInlineSnapshot(`
+        {
+          "projects": {
+            "libs/my-lib": {
+              "projectType": "library",
+              "targets": {},
+            },
+          },
+        }
+      `);
+    });
+
+    it('should create build target when the entry points point to dist files', async () => {
+      // Sibling package.json
+      await applyFilesToTempFsAndContext(tempFs, context, {
+        'libs/my-lib/tsconfig.json': `{}`,
+        'libs/my-lib/tsconfig.lib.json': `{"compilerOptions": {"outDir": "dist"}}`,
+        'libs/my-lib/package.json': JSON.stringify({
+          exports: {
+            '.': {
+              // should ignore the fact that the development condition points to source
+              development: './src/index.ts',
+              types: './dist/index.d.ts',
+              default: './dist/index.js',
+            },
+          },
+        }),
+      });
+      expect(
+        await invokeCreateNodesOnMatchingFiles(context, {
+          // Reduce noise in build snapshots by disabling default typecheck target
+          typecheck: false,
+          build: true,
+        })
+      ).toMatchInlineSnapshot(`
+        {
+          "projects": {
+            "libs/my-lib": {
+              "projectType": "library",
+              "targets": {
+                "build": {
+                  "cache": true,
+                  "command": "tsc --build tsconfig.lib.json",
+                  "dependsOn": [
+                    "^build",
+                  ],
+                  "inputs": [
+                    "production",
+                    "^production",
+                    {
+                      "externalDependencies": [
+                        "typescript",
+                      ],
+                    },
+                  ],
+                  "metadata": {
+                    "description": "Builds the project with \`tsc\`.",
+                    "help": {
+                      "command": "npx tsc --build --help",
+                      "example": {
+                        "args": [
+                          "--force",
+                        ],
+                      },
+                    },
+                    "technologies": [
+                      "typescript",
+                    ],
+                  },
+                  "options": {
+                    "cwd": "libs/my-lib",
+                  },
+                  "outputs": [
+                    "{projectRoot}/dist",
+                  ],
+                  "syncGenerators": [
+                    "@nx/js:typescript-sync",
+                  ],
+                },
+              },
+            },
+          },
+        }
+      `);
+    });
+
     it('should create a node with a build target when enabled, for a project level tsconfig.lib.json build file by default', async () => {
       // Sibling package.json
       await applyFilesToTempFsAndContext(tempFs, context, {

packages/js/src/plugins/typescript/util.ts

@@ -95,8 +95,8 @@ export function isValidPackageJsonBuildConfig(
       return isPathSourceFile(value);
     } else if (typeof value === 'object') {
       return Object.entries(value).some(([currentKey, subValue]) => {
-        // Skip types field
+        // Skip types and development conditions
-        if (currentKey === 'types') {
+        if (currentKey === 'types' || currentKey === 'development') {
           return false;
         }
         if (typeof subValue === 'string') {

packages/js/src/utils/package-json/update-package-json.spec.ts

@@ -157,6 +157,7 @@ describe('getUpdatedPackageJsonContent', () => {
         version: '0.0.1',
         exports: {
           '.': {
+            development: './src/index.ts',
             default: './src/index.js',
             import: './src/index.js',
             types: './src/index.d.ts',
@@ -190,6 +191,7 @@ describe('getUpdatedPackageJsonContent', () => {
         type: 'commonjs',
         exports: {
           '.': {
+            development: './src/index.ts',
             default: './src/index.cjs',
             types: './src/index.d.ts',
           },
@@ -228,15 +230,28 @@ describe('getUpdatedPackageJsonContent', () => {
         version: '0.0.1',
         exports: {
           '.': {
+            development: './src/index.ts',
             default: './src/index.js',
             types: './src/index.d.ts',
           },
-          './foo': './src/foo.js',
+          './foo': {
-          './bar': './src/bar.js',
+            development: './src/foo.ts',
+            default: './src/foo.js',
+          },
+          './bar': {
+            development: './src/bar.ts',
+            default: './src/bar.js',
+          },
           './package.json': './package.json',
           './migrations.json': './migrations.json',
-          './feature': './feature/index.js',
+          './feature': {
-          './feature/index': './feature/index.js',
+            development: './feature/index.ts',
+            default: './feature/index.js',
+          },
+          './feature/index': {
+            development: './feature/index.ts',
+            default: './feature/index.js',
+          },
         },
       });
 
@@ -269,15 +284,32 @@ describe('getUpdatedPackageJsonContent', () => {
         version: '0.0.1',
         exports: {
           '.': {
+            development: './src/index.ts',
             default: './src/index.js',
             import: './src/index.js',
             types: './src/index.d.ts',
           },
-          './foo': './src/foo.js',
+          './foo': {
-          './bar': './src/bar.js',
+            development: './src/foo.ts',
+            import: './src/foo.js',
+            default: './src/foo.js',
+          },
+          './bar': {
+            development: './src/bar.ts',
+            import: './src/bar.js',
+            default: './src/bar.js',
+          },
           './package.json': './package.json',
-          './feature': './feature/index.js',
+          './feature': {
-          './feature/index': './feature/index.js',
+            development: './feature/index.ts',
+            import: './feature/index.js',
+            default: './feature/index.js',
+          },
+          './feature/index': {
+            development: './feature/index.ts',
+            import: './feature/index.js',
+            default: './feature/index.js',
+          },
         },
       });
 
@@ -310,23 +342,28 @@ describe('getUpdatedPackageJsonContent', () => {
         version: '0.0.1',
         exports: {
           '.': {
+            development: './src/index.ts',
             import: './src/index.js',
             default: './src/index.cjs',
             types: './src/index.d.ts',
           },
           './foo': {
+            development: './src/foo.ts',
             import: './src/foo.js',
             default: './src/foo.cjs',
           },
           './bar': {
+            development: './src/bar.ts',
             import: './src/bar.js',
             default: './src/bar.cjs',
           },
           './feature': {
+            development: './feature/index.ts',
             import: './feature/index.js',
             default: './feature/index.cjs',
           },
           './feature/index': {
+            development: './feature/index.ts',
             import: './feature/index.js',
             default: './feature/index.cjs',
           },
@@ -364,6 +401,7 @@ describe('getUpdatedPackageJsonContent', () => {
       version: '0.0.1',
       exports: {
         '.': {
+          development: './src/index.ts',
           import: './src/index.js',
           default: './src/index.cjs',
           types: './src/index.d.ts',
@@ -400,6 +438,7 @@ describe('getUpdatedPackageJsonContent', () => {
       type: 'module',
       exports: {
         '.': {
+          development: './src/index.ts',
           default: './src/index.cjs',
           types: './src/index.d.ts',
         },
@@ -432,6 +471,7 @@ describe('getUpdatedPackageJsonContent', () => {
       type: 'commonjs',
       exports: {
         '.': {
+          development: './src/index.ts',
           default: './src/index.js',
           types: './src/index.d.ts',
         },

packages/js/src/utils/package-json/update-package-json.ts

@@ -48,6 +48,7 @@ export interface UpdatePackageJsonOption {
   buildableProjectDepsInPackageJsonType?: 'dependencies' | 'peerDependencies';
   generateLockfile?: boolean;
   packageJsonPath?: string;
+  skipDevelopmentExports?: boolean;
 }
 
 export function updatePackageJson(
@@ -113,7 +114,10 @@ export function updatePackageJson(
   }
 
   // update package specific settings
-  packageJson = getUpdatedPackageJsonContent(packageJson, options);
+  packageJson = getUpdatedPackageJsonContent(packageJson, {
+    skipDevelopmentExports: true,
+    ...options,
+  });
 
   // save files
   writeJsonFile(`${options.outputPath}/package.json`, packageJson);
@@ -285,6 +289,21 @@ export function getUpdatedPackageJsonContent(
     packageJson.exports ??=
       typeof packageJson.exports === 'string' ? {} : { ...packageJson.exports };
     packageJson.exports['./package.json'] ??= './package.json';
+
+    if (!options.skipDevelopmentExports && (hasCjsFormat || hasEsmFormat)) {
+      packageJson.exports['.'] ??= {};
+      const developmentExports = getDevelopmentExports(options);
+      for (const [exportEntry, filePath] of Object.entries(
+        developmentExports
+      )) {
+        if (!packageJson.exports[exportEntry]) {
+          packageJson.exports[exportEntry] ??= {};
+          packageJson.exports[exportEntry]['development'] ??= filePath;
+        } else if (typeof packageJson.exports[exportEntry] === 'object') {
+          packageJson.exports[exportEntry].development ??= filePath;
+        }
+      }
+    }
   }
 
   if (!options.skipTypings) {
@@ -364,6 +383,47 @@ export function getUpdatedPackageJsonContent(
   return packageJson;
 }
 
+function getDevelopmentExports(
+  options: Pick<
+    UpdatePackageJsonOption,
+    'additionalEntryPoints' | 'main' | 'projectRoot'
+  >
+) {
+  const mainRelativeDir = getRelativeDirectoryToProjectRoot(
+    options.main,
+    options.projectRoot
+  );
+  const exports: Exports = {
+    '.': mainRelativeDir + basename(options.main),
+  };
+
+  if (options.additionalEntryPoints?.length) {
+    const jsRegex = /\.[jt]sx?$/;
+
+    for (const file of options.additionalEntryPoints) {
+      const { ext: fileExt, name: fileName, base: baseName } = parse(file);
+      if (!jsRegex.test(fileExt)) {
+        continue;
+      }
+
+      const relativeDir = getRelativeDirectoryToProjectRoot(
+        file,
+        options.projectRoot
+      );
+      const sourceFilePath = relativeDir + baseName;
+      const entryRelativeDir = relativeDir.replace(/^\.\/src\//, './');
+      const entryFilePath = entryRelativeDir + fileName;
+      if (fileName === 'index') {
+        const barrelEntry = entryRelativeDir.replace(/\/$/, '');
+        exports[barrelEntry] = sourceFilePath;
+      }
+      exports[entryFilePath] = sourceFilePath;
+    }
+  }
+
+  return exports;
+}
+
 export function getOutputDir(
   options: Pick<
     UpdatePackageJsonOption,

packages/nest/src/generators/library/library.spec.ts

@@ -1,6 +1,11 @@
 import type { Tree } from '@nx/devkit';
 import * as devkit from '@nx/devkit';
-import { readJson, readProjectConfiguration, writeJson } from '@nx/devkit';
+import {
+  readJson,
+  readProjectConfiguration,
+  updateJson,
+  writeJson,
+} from '@nx/devkit';
 import { createTreeWithEmptyWorkspace } from '@nx/devkit/testing';
 import { libraryGenerator } from './library';
 
@@ -357,6 +362,7 @@ describe('lib', () => {
         compilerOptions: {
           composite: true,
           declaration: true,
+          customConditions: ['development'],
         },
       });
       writeJson(tree, 'tsconfig.json', {
@@ -498,6 +504,90 @@ describe('lib', () => {
       `);
     });
 
+    it('should create a correct package.json for buildable libraries', async () => {
+      await libraryGenerator(tree, {
+        directory: 'mylib',
+        unitTestRunner: 'jest',
+        useProjectJson: false,
+        buildable: true,
+        skipFormat: true,
+      });
+
+      expect(tree.read('mylib/package.json', 'utf-8')).toMatchInlineSnapshot(`
+        "{
+          "name": "@proj/mylib",
+          "version": "0.0.1",
+          "private": true,
+          "main": "./dist/index.js",
+          "module": "./dist/index.js",
+          "types": "./dist/index.d.ts",
+          "exports": {
+            "./package.json": "./package.json",
+            ".": {
+              "development": "./src/index.ts",
+              "types": "./dist/index.d.ts",
+              "import": "./dist/index.js",
+              "default": "./dist/index.js"
+            }
+          },
+          "nx": {
+            "targets": {
+              "lint": {
+                "executor": "@nx/eslint:lint"
+              },
+              "test": {
+                "executor": "@nx/jest:jest",
+                "outputs": [
+                  "{projectRoot}/test-output/jest/coverage"
+                ],
+                "options": {
+                  "jestConfig": "mylib/jest.config.ts"
+                }
+              },
+              "build": {
+                "executor": "@nx/js:tsc",
+                "outputs": [
+                  "{options.outputPath}"
+                ],
+                "options": {
+                  "outputPath": "dist/mylib",
+                  "tsConfig": "mylib/tsconfig.lib.json",
+                  "packageJson": "mylib/package.json",
+                  "main": "mylib/src/index.ts",
+                  "assets": [
+                    "mylib/*.md"
+                  ]
+                }
+              }
+            }
+          },
+          "dependencies": {
+            "tslib": "^2.3.0"
+          }
+        }
+        "
+      `);
+    });
+
+    it('should not set the "development" condition in exports when it does not exist in tsconfig.base.json', async () => {
+      updateJson(tree, 'tsconfig.base.json', (json) => {
+        delete json.compilerOptions.customConditions;
+        return json;
+      });
+
+      await libraryGenerator(tree, {
+        directory: 'mylib',
+        unitTestRunner: 'jest',
+        useProjectJson: false,
+        buildable: true,
+        skipFormat: true,
+      });
+
+      expect(
+        readJson(tree, 'mylib/package.json').exports['.']
+      ).not.toHaveProperty('development');
+    });
+
     it('should set "nx.name" in package.json when the user provides a name that is different than the package name', async () => {
       await libraryGenerator(tree, {
         directory: 'mylib',

packages/next/src/generators/library/library.spec.ts

@@ -133,6 +133,7 @@ describe('next library', () => {
         compilerOptions: {
           composite: true,
           declaration: true,
+          customConditions: ['development'],
         },
       });
       writeJson(tree, 'tsconfig.json', {
@@ -264,6 +265,109 @@ describe('next library', () => {
       `);
     });
 
+    it('should create a correct package.json for buildable libraries', async () => {
+      await libraryGenerator(tree, {
+        directory: 'mylib',
+        linter: Linter.EsLint,
+        skipFormat: true,
+        skipTsConfig: false,
+        unitTestRunner: 'jest',
+        style: 'css',
+        component: false,
+        useProjectJson: false,
+        buildable: true,
+      });
+
+      expect(tree.read('mylib/package.json', 'utf-8')).toMatchInlineSnapshot(`
+        "{
+          "name": "@proj/mylib",
+          "version": "0.0.1",
+          "type": "module",
+          "main": "./dist/index.esm.js",
+          "module": "./dist/index.esm.js",
+          "types": "./dist/index.esm.d.ts",
+          "exports": {
+            "./package.json": "./package.json",
+            ".": {
+              "development": "./src/index.ts",
+              "types": "./dist/index.esm.d.ts",
+              "import": "./dist/index.esm.js",
+              "default": "./dist/index.esm.js"
+            }
+          },
+          "nx": {
+            "targets": {
+              "lint": {
+                "executor": "@nx/eslint:lint"
+              },
+              "build": {
+                "executor": "@nx/rollup:rollup",
+                "outputs": [
+                  "{options.outputPath}"
+                ],
+                "options": {
+                  "outputPath": "dist/mylib",
+                  "tsConfig": "mylib/tsconfig.lib.json",
+                  "project": "mylib/package.json",
+                  "entryFile": "mylib/src/index.ts",
+                  "external": [
+                    "react",
+                    "react-dom",
+                    "react/jsx-runtime"
+                  ],
+                  "rollupConfig": "@nx/react/plugins/bundle-rollup",
+                  "compiler": "babel",
+                  "assets": [
+                    {
+                      "glob": "mylib/README.md",
+                      "input": ".",
+                      "output": "."
+                    }
+                  ]
+                }
+              },
+              "test": {
+                "executor": "@nx/jest:jest",
+                "outputs": [
+                  "{projectRoot}/test-output/jest/coverage"
+                ],
+                "options": {
+                  "jestConfig": "mylib/jest.config.ts"
+                }
+              }
+            },
+            "sourceRoot": "mylib/src",
+            "projectType": "library",
+            "tags": []
+          }
+        }
+        "
+      `);
+    });
+
+    it('should not set the "development" condition in exports when it does not exist in tsconfig.base.json', async () => {
+      updateJson(tree, 'tsconfig.base.json', (json) => {
+        delete json.compilerOptions.customConditions;
+        return json;
+      });
+
+      await libraryGenerator(tree, {
+        directory: 'mylib',
+        linter: Linter.EsLint,
+        skipFormat: true,
+        skipTsConfig: false,
+        unitTestRunner: 'jest',
+        style: 'css',
+        component: false,
+        useProjectJson: false,
+        buildable: true,
+      });
+
+      expect(
+        readJson(tree, 'mylib/package.json').exports['.']
+      ).not.toHaveProperty('development');
+    });
+
     it('should set "nx.name" in package.json when the user provides a name that is different than the package name', async () => {
       await libraryGenerator(tree, {
         directory: 'mylib',

packages/node/src/generators/library/library.spec.ts

@@ -531,6 +531,7 @@ describe('lib', () => {
         compilerOptions: {
           composite: true,
           declaration: true,
+          customConditions: ['development'],
         },
       });
       writeJson(tree, 'tsconfig.json', {
@@ -654,6 +655,61 @@ describe('lib', () => {
       `);
     });
 
+    it('should create a correct package.json for buildable libraries', async () => {
+      await libraryGenerator(tree, {
+        directory: 'mylib',
+        unitTestRunner: 'jest',
+        addPlugin: true,
+        useProjectJson: false,
+        buildable: true,
+        skipFormat: true,
+      } as Schema);
+
+      expect(tree.read('mylib/package.json', 'utf-8')).toMatchInlineSnapshot(`
+        "{
+          "name": "@proj/mylib",
+          "version": "0.0.1",
+          "private": true,
+          "main": "./dist/index.js",
+          "module": "./dist/index.js",
+          "types": "./dist/index.d.ts",
+          "exports": {
+            "./package.json": "./package.json",
+            ".": {
+              "development": "./src/index.ts",
+              "types": "./dist/index.d.ts",
+              "import": "./dist/index.js",
+              "default": "./dist/index.js"
+            }
+          },
+          "dependencies": {
+            "tslib": "^2.3.0"
+          }
+        }
+        "
+      `);
+    });
+
+    it('should not set the "development" condition in exports when it does not exist in tsconfig.base.json', async () => {
+      updateJson(tree, 'tsconfig.base.json', (json) => {
+        delete json.compilerOptions.customConditions;
+        return json;
+      });
+
+      await libraryGenerator(tree, {
+        directory: 'mylib',
+        unitTestRunner: 'jest',
+        addPlugin: true,
+        useProjectJson: false,
+        buildable: true,
+        skipFormat: true,
+      } as Schema);
+
+      expect(
+        readJson(tree, 'mylib/package.json').exports['.']
+      ).not.toHaveProperty('development');
+    });
+
     it('should set correct options for swc', async () => {
       await libraryGenerator(tree, {
         directory: 'mylib',
@@ -672,6 +728,7 @@ describe('lib', () => {
           "exports": {
             ".": {
               "default": "./dist/index.js",
+              "development": "./src/index.ts",
               "import": "./dist/index.js",
               "types": "./dist/index.d.ts",
             },

packages/plugin/src/generators/plugin/plugin.spec.ts

@@ -339,6 +339,7 @@ describe('NxPlugin Plugin Generator', () => {
         compilerOptions: {
           composite: true,
           declaration: true,
+          customConditions: ['development'],
         },
       });
       writeJson(tree, 'tsconfig.json', {
@@ -447,6 +448,7 @@ describe('NxPlugin Plugin Generator', () => {
           "exports": {
             ".": {
               "default": "./dist/index.js",
+              "development": "./src/index.ts",
               "import": "./dist/index.js",
               "types": "./dist/index.d.ts",
             },
@@ -532,6 +534,25 @@ describe('NxPlugin Plugin Generator', () => {
       `);
     });
 
+    it('should not set the "development" condition in exports when it does not exist in tsconfig.base.json', async () => {
+      updateJson(tree, 'tsconfig.base.json', (json) => {
+        delete json.compilerOptions.customConditions;
+        return json;
+      });
+
+      await pluginGenerator(
+        tree,
+        getSchema({
+          e2eTestRunner: 'jest',
+          skipFormat: true,
+        })
+      );
+
+      expect(
+        readJson(tree, 'my-plugin/package.json').exports['.']
+      ).not.toHaveProperty('development');
+    });
+
     it('should set "nx.name" in package.json when the user provides a name that is different than the package name and "useProjectJson" is "false"', async () => {
       await pluginGenerator(tree, {
         directory: 'my-plugin',

packages/react-native/src/generators/library/library.spec.ts

@@ -459,6 +459,7 @@ describe('lib', () => {
         compilerOptions: {
           composite: true,
           declaration: true,
+          customConditions: ['development'],
         },
       });
       writeJson(appTree, 'tsconfig.json', {
@@ -599,6 +600,58 @@ describe('lib', () => {
       `);
     });
 
+    it('should create a correct package.json for buildable libraries', async () => {
+      await libraryGenerator(appTree, {
+        ...defaultSchema,
+        useProjectJson: false,
+        buildable: true,
+        skipFormat: true,
+      });
+
+      expect(appTree.read('my-lib/package.json', 'utf-8'))
+        .toMatchInlineSnapshot(`
+        "{
+          "name": "@proj/my-lib",
+          "version": "0.0.1",
+          "main": "./dist/index.cjs.js",
+          "module": "./dist/index.esm.js",
+          "types": "./dist/index.esm.d.ts",
+          "exports": {
+            "./package.json": "./package.json",
+            ".": {
+              "development": "./src/index.ts",
+              "types": "./dist/index.esm.d.ts",
+              "import": "./dist/index.esm.js",
+              "default": "./dist/index.cjs.js"
+            }
+          },
+          "peerDependencies": {
+            "react": "~18.3.1",
+            "react-native": "~0.76.3"
+          }
+        }
+        "
+      `);
+    });
+
+    it('should not set the "development" condition in exports when it does not exist in tsconfig.base.json', async () => {
+      updateJson(appTree, 'tsconfig.base.json', (json) => {
+        delete json.compilerOptions.customConditions;
+        return json;
+      });
+
+      await libraryGenerator(appTree, {
+        ...defaultSchema,
+        useProjectJson: false,
+        buildable: true,
+        skipFormat: true,
+      });
+
+      expect(
+        readJson(appTree, 'my-lib/package.json').exports['.']
+      ).not.toHaveProperty('development');
+    });
+
     it('should set "nx.name" in package.json when the user provides a name that is different than the package name', async () => {
       await libraryGenerator(appTree, {
         ...defaultSchema,

packages/react-native/src/generators/library/library.ts

@@ -78,15 +78,15 @@ export async function reactNativeLibraryGeneratorInternal(
 
   createFiles(host, options);
 
+  if (options.isUsingTsSolutionConfig) {
+    await addProjectToTsSolutionWorkspace(host, options.projectRoot);
+  }
+
   const addProjectTask = await addProject(host, options);
   if (addProjectTask) {
     tasks.push(addProjectTask);
   }
 
-  if (options.isUsingTsSolutionConfig) {
-    await addProjectToTsSolutionWorkspace(host, options.projectRoot);
-  }
-
   const lintTask = await addLinting(host, {
     ...options,
     projectName: options.name,
@@ -296,6 +296,15 @@ function createFiles(host: Tree, options: NormalizedSchema) {
 function determineEntryFields(
   options: NormalizedSchema
 ): Pick<PackageJson, 'main' | 'types' | 'exports'> {
+  if (
+    options.buildable ||
+    options.publishable ||
+    !options.isUsingTsSolutionConfig
+  ) {
+    // For buildable libraries, the entries are configured by the bundler (i.e. Rollup).
+    return undefined;
+  }
+
   return {
     main: options.js ? './src/index.js' : './src/index.ts',
     types: options.js ? './src/index.js' : './src/index.ts',

packages/react/src/generators/library/library.spec.ts

@@ -939,6 +939,7 @@ module.exports = withNx(
         compilerOptions: {
           composite: true,
           declaration: true,
+          customConditions: ['development'],
         },
       });
       writeJson(tree, 'tsconfig.json', {
@@ -1246,6 +1247,7 @@ module.exports = withNx(
           "exports": {
             ".": {
               "default": "./dist/index.esm.js",
+              "development": "./src/index.ts",
               "import": "./dist/index.esm.js",
               "types": "./dist/index.esm.d.ts",
             },
@@ -1265,6 +1267,27 @@ module.exports = withNx(
       `);
     });
 
+    it('should not set the "development" condition in exports when it does not exist in tsconfig.base.json', async () => {
+      updateJson(tree, 'tsconfig.base.json', (json) => {
+        delete json.compilerOptions.customConditions;
+        return json;
+      });
+
+      await libraryGenerator(tree, {
+        ...defaultSchema,
+        bundler: 'rollup',
+        directory: 'libs/mylib',
+        publishable: true,
+        importPath: '@acme/mylib',
+        useProjectJson: false,
+        skipFormat: true,
+      });
+
+      expect(
+        readJson(tree, 'libs/mylib/package.json').exports['.']
+      ).not.toHaveProperty('development');
+    });
+
     it('should add project to workspaces when using TS solution', async () => {
       tree.write('pnpm-workspace.yaml', `packages:`);
 

packages/remix/src/generators/library/library.impl.spec.ts

@@ -149,6 +149,7 @@ describe('Remix Library Generator', () => {
         compilerOptions: {
           composite: true,
           declaration: true,
+          customConditions: ['development'],
         },
       });
       writeJson(tree, 'tsconfig.json', {
@@ -196,6 +197,59 @@ describe('Remix Library Generator', () => {
       `);
     });
 
+    it('should create a correct package.json for buildable libraries', async () => {
+      await libraryGenerator(tree, {
+        directory: 'packages/foo',
+        style: 'css',
+        addPlugin: true,
+        useProjectJson: false,
+        buildable: true,
+        skipFormat: true,
+      });
+
+      expect(tree.read('packages/foo/package.json', 'utf-8'))
+        .toMatchInlineSnapshot(`
+        "{
+          "name": "@proj/foo",
+          "version": "0.0.1",
+          "type": "module",
+          "main": "./dist/index.esm.js",
+          "module": "./dist/index.esm.js",
+          "types": "./dist/index.esm.d.ts",
+          "exports": {
+            "./package.json": "./package.json",
+            ".": {
+              "development": "./src/index.ts",
+              "types": "./dist/index.esm.d.ts",
+              "import": "./dist/index.esm.js",
+              "default": "./dist/index.esm.js"
+            }
+          }
+        }
+        "
+      `);
+    });
+
+    it('should not set the "development" condition in exports when it does not exist in tsconfig.base.json', async () => {
+      updateJson(tree, 'tsconfig.base.json', (json) => {
+        delete json.compilerOptions.customConditions;
+        return json;
+      });
+
+      await libraryGenerator(tree, {
+        directory: 'packages/foo',
+        style: 'css',
+        addPlugin: true,
+        useProjectJson: false,
+        buildable: true,
+        skipFormat: true,
+      });
+
+      expect(
+        readJson(tree, 'packages/foo/package.json').exports['.']
+      ).not.toHaveProperty('development');
+    });
+
     it('should generate server entrypoint', async () => {
       await libraryGenerator(tree, {
         directory: 'test',

packages/rollup/src/generators/configuration/configuration.ts

@@ -181,6 +181,9 @@ function updatePackageJson(
       ({ main, outputPath } = mergedTarget.options);
     }
 
+    // the file must exist in the TS solution setup
+    const tsconfigBase = readJson(tree, 'tsconfig.base.json');
+
     packageJson = getUpdatedPackageJsonContent(packageJson, {
       main,
       outputPath,
@@ -191,6 +194,10 @@ function updatePackageJson(
       format: options.format ?? ['esm'],
       outputFileExtensionForCjs: '.cjs.js',
       outputFileExtensionForEsm: '.esm.js',
+      skipDevelopmentExports:
+        !tsconfigBase.compilerOptions?.customConditions?.includes(
+          'development'
+        ),
     });
 
     // rollup has a specific declaration file generation not handled by the util above,

packages/vite/src/generators/configuration/configuration.spec.ts

@@ -331,7 +331,7 @@ describe('@nx/vite:configuration', () => {
   });
 
   describe('TS solution setup', () => {
-    beforeAll(async () => {
+    beforeEach(async () => {
       tree = createTreeWithEmptyWorkspace();
       updateJson(tree, '/package.json', (json) => {
         json.workspaces = ['packages/*', 'apps/*'];
@@ -341,6 +341,7 @@ describe('@nx/vite:configuration', () => {
         compilerOptions: {
           composite: true,
           declaration: true,
+          customConditions: ['development'],
         },
       });
       writeJson(tree, 'tsconfig.json', {
@@ -371,6 +372,7 @@ describe('@nx/vite:configuration', () => {
           "exports": {
             ".": {
               "default": "./dist/index.js",
+              "development": "./src/index.ts",
               "import": "./dist/index.js",
               "types": "./dist/index.d.ts",
             },
@@ -386,6 +388,31 @@ describe('@nx/vite:configuration', () => {
       `);
     });
 
+    it('should not set the "development" condition in exports when it does not exist in tsconfig.base.json', async () => {
+      updateJson(tree, 'tsconfig.base.json', (json) => {
+        delete json.compilerOptions.customConditions;
+        return json;
+      });
+      addProjectConfiguration(tree, 'my-lib', {
+        root: 'packages/my-lib',
+      });
+      writeJson(tree, 'packages/my-lib/tsconfig.lib.json', {});
+      writeJson(tree, 'packages/my-lib/tsconfig.json', {});
+
+      await viteConfigurationGenerator(tree, {
+        addPlugin: true,
+        uiFramework: 'none',
+        project: 'my-lib',
+        projectType: 'library',
+        newProject: true,
+        skipFormat: true,
+      });
+
+      expect(
+        readJson(tree, 'packages/my-lib/package.json').exports['.']
+      ).not.toHaveProperty('development');
+    });
+
     it('should create package.json without exports field for apps', async () => {
       addProjectConfiguration(tree, 'my-app', {
         root: 'apps/my-app',

packages/vite/src/generators/configuration/configuration.ts

@@ -219,6 +219,10 @@ function updatePackageJson(
     const rootDir = join(project.root, 'src');
     const outputPath = joinPathFragments(project.root, 'dist');
 
+    // the file must exist in the TS solution setup, which is the only case this
+    // function is called
+    const tsconfigBase = readJson(tree, 'tsconfig.base.json');
+
     packageJson = getUpdatedPackageJsonContent(packageJson, {
       main,
       outputPath,
@@ -227,6 +231,10 @@ function updatePackageJson(
       generateExportsField: true,
       packageJsonPath,
       format: ['esm'],
+      skipDevelopmentExports:
+        !tsconfigBase.compilerOptions?.customConditions?.includes(
+          'development'
+        ),
     });
   }
 

packages/vue/src/generators/library/lib/determine-entry-fields.ts

@@ -4,25 +4,23 @@ import type { NormalizedSchema } from '../schema';
 export function determineEntryFields(
   options: NormalizedSchema
 ): Pick<PackageJson, 'module' | 'types' | 'exports'> {
-  if (options.bundler === 'none') {
+  if (options.bundler !== 'none' || !options.isUsingTsSolutionConfig) {
-    return {
+    // for buildable libraries, the entries are configured by the bundler
-      module: options.js ? './src/index.js' : './src/index.ts',
+    return undefined;
-      types: options.js ? './src/index.js' : './src/index.ts',
-      exports: {
-        '.': options.js
-          ? './src/index.js'
-          : {
-              types: './src/index.ts',
-              import: './src/index.ts',
-              default: './src/index.ts',
-            },
-        './package.json': './package.json',
-      },
-    };
   }
 
   return {
-    module: './dist/index.mjs',
+    module: options.js ? './src/index.js' : './src/index.ts',
-    types: './dist/index.d.ts',
+    types: options.js ? './src/index.js' : './src/index.ts',
+    exports: {
+      '.': options.js
+        ? './src/index.js'
+        : {
+            types: './src/index.ts',
+            import: './src/index.ts',
+            default: './src/index.ts',
+          },
+      './package.json': './package.json',
+    },
   };
 }

packages/vue/src/generators/library/library.spec.ts

@@ -521,6 +521,7 @@ module.exports = [
         compilerOptions: {
           composite: true,
           declaration: true,
+          customConditions: ['development'],
         },
       });
       writeJson(tree, 'tsconfig.json', {
@@ -585,6 +586,39 @@ module.exports = [
           "nx",
         ]
       `);
+      expect(tree.read('my-lib/package.json', 'utf-8')).toMatchInlineSnapshot(`
+        "{
+          "name": "@proj/my-lib",
+          "version": "0.0.1",
+          "module": "./src/index.ts",
+          "types": "./src/index.ts",
+          "exports": {
+            ".": {
+              "types": "./src/index.ts",
+              "import": "./src/index.ts",
+              "default": "./src/index.ts"
+            },
+            "./package.json": "./package.json"
+          },
+          "nx": {
+            "targets": {
+              "lint": {
+                "executor": "@nx/eslint:lint"
+              },
+              "test": {
+                "executor": "@nx/vite:test",
+                "outputs": [
+                  "{options.reportsDirectory}"
+                ],
+                "options": {
+                  "reportsDirectory": "../coverage/my-lib"
+                }
+              }
+            }
+          }
+        }
+        "
+      `);
       expect(readJson(tree, 'my-lib/tsconfig.json')).toMatchInlineSnapshot(`
         {
           "extends": "../tsconfig.base.json",
@@ -690,6 +724,60 @@ module.exports = [
       `);
     });
 
+    it('should create a correct package.json for buildable libraries', async () => {
+      await libraryGenerator(tree, {
+        ...defaultSchema,
+        setParserOptionsProject: true,
+        linter: 'eslint',
+        addPlugin: true,
+        useProjectJson: false,
+        bundler: 'vite',
+        skipFormat: true,
+      });
+
+      expect(tree.read('my-lib/package.json', 'utf-8')).toMatchInlineSnapshot(`
+        "{
+          "name": "@proj/my-lib",
+          "version": "0.0.1",
+          "type": "module",
+          "main": "./dist/index.js",
+          "module": "./dist/index.js",
+          "types": "./dist/index.d.ts",
+          "exports": {
+            "./package.json": "./package.json",
+            ".": {
+              "development": "./src/index.ts",
+              "types": "./dist/index.d.ts",
+              "import": "./dist/index.js",
+              "default": "./dist/index.js"
+            }
+          }
+        }
+        "
+      `);
+    });
+
+    it('should not set the "development" condition in exports when it does not exist in tsconfig.base.json', async () => {
+      updateJson(tree, 'tsconfig.base.json', (json) => {
+        delete json.compilerOptions.customConditions;
+        return json;
+      });
+
+      await libraryGenerator(tree, {
+        ...defaultSchema,
+        setParserOptionsProject: true,
+        linter: 'eslint',
+        addPlugin: true,
+        useProjectJson: false,
+        bundler: 'vite',
+        skipFormat: true,
+      });
+
+      expect(
+        readJson(tree, 'my-lib/package.json').exports['.']
+      ).not.toHaveProperty('development');
+    });
+
     it('should set "nx.name" in package.json when the user provides a name that is different than the package name', async () => {
       await libraryGenerator(tree, {
         ...defaultSchema,