Implement assumptions defined in the babel/rfcs#5 RFC

- `mutableTemplateObject` and `ignoreToPrimitiveHint` (#12408)
- `setClassMethods` (#12407)
- `setComputedProperties` (#12490)
- `ignoreFunctionLength` (#12491)
- `noDocumentAll` (#12481)
- `iterableIsArray` and `arrayLikeIsIterable` (#12489)
- `pureGetters` (#12504)
- `skipForOfIteratorClosing` (#12496)
- `objectRestNoSymbols`, `setSpreadProperties` and `pureGetters` (#12505)
- `noNewArrows` (#12613, #12793)
- `setPublicClassFields` and `privateFieldsAsProperties` (#12497)
- `constantReexports` and `enumerableModuleMeta` (#12618)
- `constantSuper`, `superIsCallableConstructor` and `noClassCalls` (#12726)

Co-authored-by: Justin Ridgewell <justin@ridgewell.name>
Co-authored-by: Huáng Jùnliàng <JLHwung@users.noreply.github.com>

packages/babel-plugin-transform-computed-properties/src/index.js

@@ -4,8 +4,10 @@ import { template, types as t } from "@babel/core";
 export default declare((api, options) => {
   api.assertVersion(7);
 
-  const { loose } = options;
-  const pushComputedProps = loose
+  const setComputedProperties =
+    api.assumption("setComputedProperties") ?? options.loose;
+
+  const pushComputedProps = setComputedProperties
     ? pushComputedPropsLoose
     : pushComputedPropsSpec;
 

packages/babel-plugin-transform-computed-properties/test/fixtures/assumption-setComputedProperties/options.json

@@ -0,0 +1,9 @@
+{
+  "plugins": [
+    "external-helpers",
+    "transform-computed-properties"
+  ],
+  "assumptions": {
+    "setComputedProperties": true
+  }
+}

packages/babel-plugin-transform-computed-properties/test/fixtures/loose/setComputedProperties/input.js

@@ -0,0 +1,4 @@
+var obj = {
+  ["x" + foo]: "heh",
+  ["y" + bar]: "noo"
+};

packages/babel-plugin-transform-computed-properties/test/fixtures/loose/setComputedProperties/output.js

@@ -0,0 +1,3 @@
+var _obj;
+
+var obj = (_obj = {}, _obj["x" + foo] = "heh", _obj["y" + bar] = "noo", _obj);