Implement a new utility module for injecting module imports.

packages/babel-core/src/transformation/internal-plugins/block-hoist.js

@@ -10,6 +10,7 @@ export default {
    *  - 1 Default node position
    *  - 2 Priority over normal nodes
    *  - 3 We want this to be at the **very** top
+   *  - 4 Reserved for the helpers used to implement module imports.
    */
 
   name: "internal.blockHoist",

packages/babel-helper-module-imports/.npmignore

@@ -0,0 +1,3 @@
+src
+test
+*.log

packages/babel-helper-module-imports/README.md

@@ -0,0 +1,27 @@
+# babel-helper-module-imports
+
+## Usage
+
+### Adding a named impport
+
+```
+import { addNamed } from "babel-helper-module-imports";
+
+export default function({ types: t }) {
+  return {
+    visitor: {
+      ReferencedIdentifier(path) {
+        let importName = this.importName;
+        if (importName) {
+          importName = t.cloneDeep(importName);
+        } else {
+          // require('bluebird').coroutine
+          importName = this.importName = addName(path, 'coroutine', 'bluebird');
+        }
+
+        path.replaceWith(importName);
+      }
+    },
+  };
+}
+```

packages/babel-helper-module-imports/package.json

@@ -0,0 +1,14 @@
+{
+  "name": "babel-helper-module-imports",
+  "version": "7.0.0-beta.2",
+  "description": "Babel helper functions for inserting module loads",
+  "author": "Logan Smyth <loganfsmyth@gmail.com>",
+  "homepage": "https://babeljs.io/",
+  "license": "MIT",
+  "repository": "https://github.com/babel/babel/tree/master/packages/babel-helper-module-imports",
+  "main": "lib/index.js",
+  "dependencies": {
+    "babel-types": "7.0.0-beta.2",
+    "lodash": "^4.2.0"
+  }
+}

packages/babel-helper-module-imports/src/import-builder.js

@@ -0,0 +1,142 @@
+import assert from "assert";
+import * as t from "babel-types";
+
+/**
+ * A class to track and accumulate mutations to the AST that will eventually
+ * output a new require/import statement list.
+ */
+export default class ImportBuilder {
+  _statements = [];
+  _resultName = null;
+
+  _scope = null;
+  _file = null;
+
+  constructor(importedSource, scope, file) {
+    this._scope = scope;
+    this._file = file;
+    this._importedSource = importedSource;
+  }
+
+  done() {
+    return {
+      statements: this._statements,
+      resultName: this._resultName,
+    };
+  }
+
+  import() {
+    const importedSource = this._file.resolveModuleSource(this._importedSource);
+
+    this._statements.push(
+      t.importDeclaration([], t.stringLiteral(importedSource)),
+    );
+    return this;
+  }
+
+  require() {
+    const importedSource = this._file.resolveModuleSource(this._importedSource);
+
+    this._statements.push(
+      t.expressionStatement(
+        t.callExpression(t.identifier("require"), [
+          t.stringLiteral(importedSource),
+        ]),
+      ),
+    );
+    return this;
+  }
+
+  namespace(name) {
+    name = this._scope.generateUidIdentifier(name);
+
+    const statement = this._statements[this._statements.length - 1];
+    assert(statement.type === "ImportDeclaration");
+    assert(statement.specifiers.length === 0);
+    statement.specifiers = [t.importNamespaceSpecifier(name)];
+    this._resultName = t.clone(name);
+    return this;
+  }
+  default(name) {
+    name = this._scope.generateUidIdentifier(name);
+    const statement = this._statements[this._statements.length - 1];
+    assert(statement.type === "ImportDeclaration");
+    assert(statement.specifiers.length === 0);
+    statement.specifiers = [t.importDefaultSpecifier(name)];
+    this._resultName = t.clone(name);
+    return this;
+  }
+  named(name, importName) {
+    if (importName === "default") return this.default(name);
+
+    name = this._scope.generateUidIdentifier(name);
+    const statement = this._statements[this._statements.length - 1];
+    assert(statement.type === "ImportDeclaration");
+    assert(statement.specifiers.length === 0);
+    statement.specifiers = [t.importSpecifier(name, t.identifier(importName))];
+    this._resultName = t.clone(name);
+    return this;
+  }
+
+  var(name) {
+    name = this._scope.generateUidIdentifier(name);
+    let statement = this._statements[this._statements.length - 1];
+    if (statement.type !== "ExpressionStatement") {
+      assert(this._resultName);
+      statement = t.expressionStatement(this._resultName);
+      this._statements.push(statement);
+    }
+    this._statements[
+      this._statements.length - 1
+    ] = t.variableDeclaration("var", [
+      t.variableDeclarator(name, statement.expression),
+    ]);
+    this._resultName = t.clone(name);
+    return this;
+  }
+
+  defaultInterop() {
+    return this._interop(this._file.addHelper("interopRequireDefault"));
+  }
+  wildcardInterop() {
+    return this._interop(this._file.addHelper("interopRequireWildcard"));
+  }
+
+  _interop(callee) {
+    const statement = this._statements[this._statements.length - 1];
+    if (statement.type === "ExpressionStatement") {
+      statement.expression = t.callExpression(callee, [statement.expression]);
+    } else if (statement.type === "VariableDeclaration") {
+      assert(statement.declarations.length === 1);
+      statement.declarations[0].init = t.callExpression(callee, [
+        statement.declarations[0].init,
+      ]);
+    } else {
+      assert.fail("Unexpected type.");
+    }
+    return this;
+  }
+
+  prop(name) {
+    const statement = this._statements[this._statements.length - 1];
+    if (statement.type === "ExpressionStatement") {
+      statement.expression = t.memberExpression(
+        statement.expression,
+        t.identifier(name),
+      );
+    } else if (statement.type === "VariableDeclaration") {
+      assert(statement.declarations.length === 1);
+      statement.declarations[0].init = t.memberExpression(
+        statement.declarations[0].init,
+        t.identifier(name),
+      );
+    } else {
+      assert.fail("Unexpected type:" + statement.type);
+    }
+    return this;
+  }
+
+  read(name) {
+    this._resultName = t.memberExpression(this._resultName, t.identifier(name));
+  }
+}

packages/babel-helper-module-imports/src/import-injector.js

@@ -0,0 +1,425 @@
+import assert from "assert";
+import * as t from "babel-types";
+
+import ImportBuilder from "./import-builder";
+import isModule from "./is-module";
+
+export type ImportOptions = {
+  /**
+   * The module being referenced.
+   */
+  importedSource: string | null,
+
+  /**
+   * The type of module being imported:
+   *
+   *  * 'es6'      - An ES6 module.
+   *  * 'commonjs' - A CommonJS module. (Default)
+   */
+  importedType: "es6" | "commonjs",
+
+  /**
+   * The type of interop behavior for namespace/default/named when loading
+   * CommonJS modules.
+   *
+   * ## 'babel' (Default)
+   *
+   * Load using Babel's interop.
+   *
+   * If '.__esModule' is true, treat as 'compiled', else:
+   *
+   * * Namespace: A copy of the module.exports with .default
+   *     populated by the module.exports object.
+   * * Default: The module.exports value.
+   * * Named: The .named property of module.exports.
+   *
+   * The 'ensureLiveReference' has no effect on the liveness of these.
+   *
+   * ## 'compiled'
+   *
+   * Assume the module is ES6 compiled to CommonJS. Useful to avoid injecting
+   * interop logic if you are confident that the module is a certain format.
+   *
+   * * Namespace: The root module.exports object.
+   * * Default: The .default property of the namespace.
+   * * Named: The .named property of the namespace.
+   *
+   * Will return erroneous results if the imported module is _not_ compiled
+   * from ES6 with Babel.
+   *
+   * ## 'uncompiled'
+   *
+   * Assume the module is _not_ ES6 compiled to CommonJS. Used a simplified
+   * access pattern that doesn't require additional function calls.
+   *
+   * Will return erroneous results if the imported module _is_ compiled
+   * from ES6 with Babel.
+   *
+   * * Namespace: The module.exports object.
+   * * Default: The module.exports object.
+   * * Named: The .named property of module.exports.
+   */
+  importedInterop: "babel" | "node" | "compiled" | "uncompiled",
+
+  /**
+   * The type of CommonJS interop included in the environment that will be
+   * loading the output code.
+   *
+   *  * 'babel' - CommonJS modules load with Babel's interop. (Default)
+   *  * 'node'  - CommonJS modules load with Node's interop.
+   *
+   * See descriptions in 'importedInterop' for more details.
+   */
+  importingInterop: "babel" | "node",
+
+  /**
+   * Define whether we explicitly care that the import be a live reference.
+   * Only applies when importing default and named imports, not the namespace.
+   *
+   *  * true  - Force imported values to be live references.
+   *  * false - No particular requirements. Keeps the code simplest. (Default)
+   */
+  ensureLiveReference: boolean,
+
+  /**
+   * Define if we explicitly care that the result not be a property reference.
+   *
+   *  * true  - Force calls to exclude context. Useful if the value is going to
+   *            be used as function callee.
+   *  * false - No particular requirements for context of the access. (Default)
+   */
+  ensureNoContext: boolean,
+};
+
+/**
+ * A general helper classes add imports via transforms. See README for usage.
+ */
+export default class ImportInjector {
+  /**
+   * The path used for manipulation.
+   */
+  _programPath: NodePath;
+
+  /**
+   * The scope used to generate unique variable names.
+   */
+  _programScope;
+
+  /**
+   * The file used to inject helpers and resolve paths.
+   */
+  _file;
+
+  /**
+   * The default options to use with this instance when imports are added.
+   */
+  _defaultOpts: ImportOptions = {
+    importedSource: null,
+    importedType: "commonjs",
+    importedInterop: "babel",
+    importingInterop: "babel",
+    ensureLiveReference: false,
+    ensureNoContext: false,
+  };
+
+  constructor(path, importedSource, opts) {
+    const programPath = path.find(p => p.isProgram());
+
+    this._programPath = programPath;
+    this._programScope = programPath.scope;
+    this._file = programPath.hub.file;
+
+    this._defaultOpts = this._applyDefaults(importedSource, opts, true);
+  }
+
+  addDefault(importedSourceIn, opts) {
+    return this.addNamed("default", importedSourceIn, opts);
+  }
+
+  addNamed(importName, importedSourceIn, opts) {
+    assert(typeof importName === "string");
+
+    return this._generateImport(
+      this._applyDefaults(importedSourceIn, opts),
+      importName,
+    );
+  }
+
+  addNamespace(importedSourceIn, opts) {
+    return this._generateImport(
+      this._applyDefaults(importedSourceIn, opts),
+      null,
+    );
+  }
+
+  addSideEffect(importedSourceIn, opts) {
+    return this._generateImport(
+      this._applyDefaults(importedSourceIn, opts),
+      false,
+    );
+  }
+
+  _applyDefaults(importedSource, opts, isInit = false) {
+    const optsList = [];
+    if (typeof importedSource === "string") {
+      optsList.push({ importedSource });
+      optsList.push(opts);
+    } else {
+      assert(!opts, "Unexpected secondary arguments.");
+
+      optsList.push(importedSource);
+    }
+
+    const newOpts = Object.assign({}, this._defaultOpts);
+    for (const opts of optsList) {
+      if (!opts) continue;
+      Object.keys(newOpts).forEach(key => {
+        if (opts[key] !== undefined) newOpts[key] = opts[key];
+      });
+
+      if (!isInit) {
+        if (opts.nameHint !== undefined) newOpts.nameHint = opts.nameHint;
+        if (opts.blockHoist !== undefined) newOpts.blockHoist = opts.blockHoist;
+      }
+    }
+    return newOpts;
+  }
+
+  _generateImport(opts, importName) {
+    const isDefault = importName === "default";
+    const isNamed = !!importName && !isDefault;
+    const isNamespace = importName === null;
+
+    const {
+      importedSource,
+      importedType,
+      importedInterop,
+      importingInterop,
+      ensureLiveReference,
+      ensureNoContext,
+
+      // Provide a hint for generateUidIdentifier for the local variable name
+      // to use for the import, if the code will generate a simple assignment
+      // to a variable.
+      nameHint = importName,
+
+      // Not meant for public usage. Allows code that absolutely must control
+      // ordering to set a specific hoist value on the import nodes.
+      blockHoist,
+    } = opts;
+
+    const isMod = isModule(this._programPath, true);
+    const isModuleForNode = isMod && importingInterop === "node";
+    const isModuleForBabel = isMod && importingInterop === "babel";
+
+    const builder = new ImportBuilder(
+      importedSource,
+      this._programScope,
+      this._file,
+    );
+
+    if (importedType === "es6") {
+      if (!isModuleForNode && !isModuleForBabel) {
+        throw new Error("Cannot import an ES6 module from CommonJS");
+      }
+
+      // import * as namespace from ''; namespace
+      // import def from ''; def
+      // import { named } from ''; named
+      builder.import();
+      if (isNamespace) {
+        builder.namespace("namespace");
+      } else if (isDefault || isNamed) {
+        builder.named(nameHint, importName);
+      }
+    } else if (importedType !== "commonjs") {
+      throw new Error(`Unexpected interopType "${importedType}"`);
+    } else if (importedInterop === "babel") {
+      if (isModuleForNode) {
+        // import _tmp from ''; var namespace = interopRequireWildcard(_tmp); namespace
+        // import _tmp from ''; var def = interopRequireDefault(_tmp).default; def
+        // import _tmp from ''; _tmp.named
+
+        builder.import();
+        if (isNamespace) {
+          builder
+            .default("es6Default")
+            .var(nameHint || "namespace")
+            .wildcardInterop();
+        } else if (isDefault) {
+          if (ensureLiveReference) {
+            builder
+              .default("es6Default")
+              .var("namespace")
+              .defaultInterop()
+              .read("default");
+          } else {
+            builder
+              .default("es6Default")
+              .var(nameHint)
+              .defaultInterop()
+              .prop(importName);
+          }
+        } else if (isNamed) {
+          builder.default("es6Default").read(importName);
+        }
+      } else if (isModuleForBabel) {
+        // import * as namespace from ''; namespace
+        // import def from ''; def
+        // import { named } from ''; named
+        builder.import();
+        if (isNamespace) {
+          builder.namespace("namespace");
+        } else if (isDefault || isNamed) {
+          builder.named(nameHint, importName);
+        }
+      } else {
+        // var namespace = interopRequireWildcard(require(''));
+        // var def = interopRequireDefault(require('')).default; def
+        // var named = require('').named; named
+        builder.require();
+        if (isNamespace) {
+          builder.var("namespace").wildcardInterop();
+        } else if ((isDefault || isNamed) && ensureLiveReference) {
+          builder.var("namespace").read(importName);
+
+          if (isDefault) builder.defaultInterop();
+        } else if (isDefault) {
+          builder
+            .var(nameHint)
+            .defaultInterop()
+            .prop(importName);
+        } else if (isNamed) {
+          builder.var(nameHint).prop(importName);
+        }
+      }
+    } else if (importedInterop === "compiled") {
+      if (isModuleForNode) {
+        // import namespace from ''; namespace
+        // import namespace from ''; namespace.default
+        // import namespace from ''; namespace.named
+
+        builder.import();
+        if (isNamespace) {
+          builder.default("namespace");
+        } else if (isDefault || isNamed) {
+          builder.default("namespace").read(importName);
+        }
+      } else if (isModuleForBabel) {
+        // import * as namespace from ''; namespace
+        // import def from ''; def
+        // import { named } from ''; named
+        // Note: These lookups will break if the module has no __esModule set,
+        // hence the warning that 'compiled' will not work on standard CommonJS.
+
+        builder.import();
+        if (isNamespace) {
+          builder.namespace("namespace");
+        } else if (isDefault || isNamed) {
+          builder.named(nameHint, importName);
+        }
+      } else {
+        // var namespace = require(''); namespace
+        // var namespace = require(''); namespace.default
+        // var namespace = require(''); namespace.named
+        // var named = require('').named;
+
+        builder.require();
+        if (isNamespace) {
+          builder.var("namespace");
+        } else if (isDefault || isNamed) {
+          if (ensureLiveReference) {
+            builder.var("namespace").read(importName);
+          } else {
+            builder.prop(importName).var(nameHint);
+          }
+        }
+      }
+    } else if (importedInterop === "uncompiled") {
+      if (isDefault && ensureLiveReference) {
+        throw new Error("No live reference for commonjs default");
+      }
+
+      if (isModuleForNode) {
+        // import namespace from ''; namespace
+        // import def from ''; def;
+        // import namespace from ''; namespace.named
+
+        builder.import();
+        if (isNamespace) {
+          builder.default("namespace");
+        } else if (isDefault) {
+          builder.default(nameHint);
+        } else if (isNamed) {
+          builder.default("namespace").read(importName);
+        }
+      } else if (isModuleForBabel) {
+        // import namespace from '';
+        // import def from '';
+        // import { named } from ''; named;
+        // Note: These lookups will break if the module has __esModule set,
+        // hence the warning that 'uncompiled' will not work on ES6 transpiled
+        // to CommonJS.
+
+        builder.import();
+        if (isNamespace) {
+          builder.default("namespace");
+        } else if (isDefault) {
+          builder.default(nameHint);
+        } else if (isNamed) {
+          builder.named(nameHint, importName);
+        }
+      } else {
+        // var namespace = require(''); namespace
+        // var def = require(''); def
+        // var namespace = require(''); namespace.named
+        // var named = require('').named;
+
+        builder.require();
+        if (isNamespace) {
+          builder.var("namespace");
+        } else if (isDefault) {
+          builder.var(nameHint);
+        } else if (isNamed) {
+          if (ensureLiveReference) {
+            builder.var("namespace").read(importName);
+          } else {
+            builder.var(nameHint).prop(importName);
+          }
+        }
+      }
+    } else {
+      throw new Error(`Unknown importedInterop "${importedInterop}".`);
+    }
+
+    const { statements, resultName } = builder.done();
+
+    this._insertStatements(statements, blockHoist);
+
+    if (
+      (isDefault || isNamed) &&
+      ensureNoContext &&
+      resultName.type !== "Identifier"
+    ) {
+      return t.sequenceExpression([t.numericLiteral(0), resultName]);
+    }
+    return resultName;
+  }
+
+  _insertStatements(statements, blockHoist = 3) {
+    statements.forEach(node => {
+      node._blockHoist = blockHoist;
+    });
+
+    const targetPath = this._programPath.get("body").filter(p => {
+      const val = p.node._blockHoist;
+      return Number.isFinite(val) && val < 4;
+    })[0];
+
+    if (targetPath) {
+      targetPath.insertBefore(statements);
+    } else {
+      this._programPath.unshiftContainer("body", statements);
+    }
+  }
+}

packages/babel-helper-module-imports/src/index.js

@@ -0,0 +1,21 @@
+import ImportInjector from "./import-injector";
+
+export { ImportInjector };
+
+export { default as isModule } from "./is-module";
+
+export function addDefault(path, importedSource, opts) {
+  return new ImportInjector(path).addDefault(importedSource, opts);
+}
+
+export function addNamed(path, name, importedSource, opts) {
+  return new ImportInjector(path).addNamed(name, importedSource, opts);
+}
+
+export function addNamespace(path, importedSource, opts) {
+  return new ImportInjector(path).addNamespace(importedSource, opts);
+}
+
+export function addSideEffect(path, importedSource, opts) {
+  return new ImportInjector(path).addSideEffect(importedSource, opts);
+}

packages/babel-helper-module-imports/src/is-module.js

@@ -0,0 +1,31 @@
+/**
+ * A small utility to check if a file qualifies as a module, based on a few
+ * possible conditions.
+ */
+export default function isModule(
+  path: NodePath,
+  requireUnambiguous: boolean = false,
+) {
+  const { sourceType } = path.node;
+  if (sourceType !== "module" && sourceType !== "script") {
+    throw path.buildCodeFrameError(
+      `Unknown sourceType "${sourceType}", cannot transform.`,
+    );
+  }
+
+  const filename = path.hub.file.opts.filename;
+  if (/\.mjs$/.test(filename)) {
+    requireUnambiguous = false;
+  }
+
+  return (
+    path.node.sourceType === "module" &&
+    (!requireUnambiguous || isUnambiguousModule(path))
+  );
+}
+
+// This approach is not ideal. It is here to preserve compatibility for now,
+// but really this should just return true or be deleted.
+function isUnambiguousModule(path) {
+  return path.get("body").some(p => p.isModuleDeclaration());
+}

packages/babel-helper-module-transforms/package.json

@@ -8,6 +8,7 @@
   "repository": "https://github.com/babel/babel/tree/master/packages/babel-helper-module-transforms",
   "main": "lib/index.js",
   "dependencies": {
+    "babel-helper-module-imports": "7.0.0-beta.2",
     "babel-template": "7.0.0-beta.2",
     "babel-types": "7.0.0-beta.2",
     "lodash": "^4.2.0"

packages/babel-helper-module-transforms/src/index.js

@@ -3,6 +3,8 @@ import * as t from "babel-types";
 import template from "babel-template";
 import chunk from "lodash/chunk";
 
+import { isModule } from "babel-helper-module-imports";
+
 import rewriteThis from "./rewrite-this";
 import rewriteLiveReferences from "./rewrite-live-references";
 import normalizeAndLoadModuleMetadata, {
@@ -10,32 +12,7 @@ import normalizeAndLoadModuleMetadata, {
   isSideEffectImport,
 } from "./normalize-and-load-metadata";
 
-export { hasExports, isSideEffectImport };
+export { hasExports, isSideEffectImport, isModule };
-
-export function isModule(path: NodePath, requireUnambiguous: boolean = false) {
-  const { sourceType } = path.node;
-  if (sourceType !== "module" && sourceType !== "script") {
-    throw path.buildCodeFrameError(
-      `Unknown sourceType "${sourceType}", cannot transform.`,
-    );
-  }
-
-  const filename = path.hub.file.opts.filename;
-  if (/\.mjs$/.test(filename)) {
-    requireUnambiguous = false;
-  }
-
-  return (
-    path.node.sourceType === "module" &&
-    (!requireUnambiguous || isUnambiguousModule(path))
-  );
-}
-
-// This approach is not ideal. It is here to preserve compatibility for now,
-// but really this should just return true or be deleted.
-function isUnambiguousModule(path) {
-  return path.get("body").some(p => p.isModuleDeclaration());
-}
 
 /**
  * Perform all of the generic ES6 module rewriting needed to handle initial