[babel 8] Remove loose and spec options from preset-env (#16043)

* [babel 8] Remove `loose` and `spec` options from `preset-env`

* Add tests for good error messages

* [babel 8] Remove env's loose special-handling in class features plugins

packages/babel-helper-create-class-features-plugin/src/features.ts

@@ -37,16 +37,26 @@ const featuresSameLoose = new Map([
 const featuresKey = "@babel/plugin-class-features/featuresKey";
 const looseKey = "@babel/plugin-class-features/looseKey";
 
-// See /~https://github.com/babel/babel/issues/11622.
-// Since preset-env sets loose for the fields and private methods plugins, it can
-// cause conflicts with the loose mode set by an explicit plugin in the config.
-// To solve this problem, we ignore preset-env's loose mode if another plugin
-// explicitly sets it
-// The code to handle this logic doesn't check that "low priority loose" is always
-// the same. However, it is only set by the preset and not directly by users:
-// unless someone _wants_ to break it, it shouldn't be a problem.
-const looseLowPriorityKey =
-  "@babel/plugin-class-features/looseLowPriorityKey/#__internal__@babel/preset-env__please-overwrite-loose-instead-of-throwing";
+if (!process.env.BABEL_8_BREAKING) {
+  // See /~https://github.com/babel/babel/issues/11622.
+  // Since preset-env sets loose for the fields and private methods plugins, it can
+  // cause conflicts with the loose mode set by an explicit plugin in the config.
+  // To solve this problem, we ignore preset-env's loose mode if another plugin
+  // explicitly sets it
+  // The code to handle this logic doesn't check that "low priority loose" is always
+  // the same. However, it is only set by the preset and not directly by users:
+  // unless someone _wants_ to break it, it shouldn't be a problem.
+  // eslint-disable-next-line no-var
+  var looseLowPriorityKey =
+    "@babel/plugin-class-features/looseLowPriorityKey/#__internal__@babel/preset-env__please-overwrite-loose-instead-of-throwing";
+}
+
+if (!process.env.BABEL_8_BREAKING) {
+  // eslint-disable-next-line no-var
+  var canIgnoreLoose = function (file: File, feature: number) {
+    return !!(file.get(looseLowPriorityKey) & feature);
+  };
+}
 
 export function enableFeature(file: File, feature: number, loose: boolean) {
   // We can't blindly enable the feature because, if it was already set,
@@ -55,7 +65,12 @@ export function enableFeature(file: File, feature: number, loose: boolean) {
   //   @babel/plugin-class-properties { loose: false }
   // is transformed in loose mode.
   // We only enabled the feature if it was previously disabled.
-  if (!hasFeature(file, feature) || canIgnoreLoose(file, feature)) {
+  if (process.env.BABEL_8_BREAKING) {
+    if (!hasFeature(file, feature)) {
+      file.set(featuresKey, file.get(featuresKey) | feature);
+      setLoose(file, feature, loose);
+    }
+  } else if (!hasFeature(file, feature) || canIgnoreLoose(file, feature)) {
     file.set(featuresKey, file.get(featuresKey) | feature);
     if (
       // @ts-expect-error comparing loose with internal private magic string
@@ -77,28 +92,31 @@ export function enableFeature(file: File, feature: number, loose: boolean) {
   }
 
   let resolvedLoose: boolean | undefined;
-  let higherPriorityPluginName: string | undefined;
-
   for (const [mask, name] of featuresSameLoose) {
     if (!hasFeature(file, mask)) continue;
+    if (!process.env.BABEL_8_BREAKING) {
+      if (canIgnoreLoose(file, mask)) continue;
+    }
 
     const loose = isLoose(file, mask);
 
-    if (canIgnoreLoose(file, mask)) {
-      continue;
-    } else if (resolvedLoose === !loose) {
+    if (resolvedLoose === !loose) {
       throw new Error(
         "'loose' mode configuration must be the same for @babel/plugin-transform-class-properties, " +
           "@babel/plugin-transform-private-methods and " +
           "@babel/plugin-transform-private-property-in-object (when they are enabled).",
       );
     } else {
       resolvedLoose = loose;
-      higherPriorityPluginName = name;
+
+      if (!process.env.BABEL_8_BREAKING) {
+        // eslint-disable-next-line no-var
+        var higherPriorityPluginName = name;
+      }
     }
   }
 
-  if (resolvedLoose !== undefined) {
+  if (!process.env.BABEL_8_BREAKING && resolvedLoose !== undefined) {
     for (const [mask, name] of featuresSameLoose) {
       if (hasFeature(file, mask) && isLoose(file, mask) !== resolvedLoose) {
         setLoose(file, mask, resolvedLoose);
@@ -129,11 +147,9 @@ function setLoose(file: File, feature: number, loose: boolean) {
   if (loose) file.set(looseKey, file.get(looseKey) | feature);
   else file.set(looseKey, file.get(looseKey) & ~feature);
 
-  file.set(looseLowPriorityKey, file.get(looseLowPriorityKey) & ~feature);
-}
-
-function canIgnoreLoose(file: File, feature: number) {
-  return !!(file.get(looseLowPriorityKey) & feature);
+  if (!process.env.BABEL_8_BREAKING) {
+    file.set(looseLowPriorityKey, file.get(looseLowPriorityKey) & ~feature);
+  }
 }
 
 export function shouldTransform(path: NodePath<t.Class>, file: File): boolean {

packages/babel-helper-create-class-features-plugin/test/fixtures/plugin-proposal-class-properties/warn-loose-and-assumptions-preset-env/options.json → packages/babel-helper-create-class-features-plugin/test/fixtures/plugin-proposal-class-properties/warn-loose-and-assumptions-preset-env-babel-7/options.json

@@ -1,4 +1,5 @@
 {
+  "BABEL_8_BREAKING": false,
   "validateLogs": true,
   "presets": [["env", { "loose": true, "shippedProposals": true }]],
   "assumptions": {

packages/babel-plugin-transform-flow-comments/test/fixtures/flow-comments/transformed-class-method-loose-return-type-annotation/options.json

@@ -1,4 +1,6 @@
 {
-  "presets": [["env", { "loose": true, "targets": { "browsers": "ie 6" } }]],
-  "plugins": ["transform-flow-comments"]
+  "plugins": [
+    "transform-flow-comments",
+    ["transform-classes", { "loose": true }]
+  ]
 }

packages/babel-plugin-transform-flow-comments/test/fixtures/flow-comments/transformed-class-method-loose-return-type-annotation/output.js

@@ -1,5 +1,5 @@
 // @flow
-var C = /*#__PURE__*/function () {
+let C = /*#__PURE__*/function () {
   "use strict";
 
   function C() {}

packages/babel-plugin-transform-flow-strip-types/test/fixtures/regression/transformed-class-method-loose-return-type-annotation/options.json

@@ -1,4 +1,6 @@
 {
-  "presets": [["env", { "loose": true, "targets": { "browsers": "ie 6" } }]],
-  "plugins": ["transform-flow-strip-types"]
+  "plugins": [
+    "transform-flow-strip-types",
+    ["transform-classes", { "loose": true }]
+  ]
 }

packages/babel-plugin-transform-flow-strip-types/test/fixtures/regression/transformed-class-method-loose-return-type-annotation/output.js

@@ -1,4 +1,4 @@
-var C = /*#__PURE__*/function () {
+let C = /*#__PURE__*/function () {
   "use strict";
 
   function C() {}

packages/babel-preset-env/src/index.ts

@@ -1,6 +1,5 @@
 import semver, { type SemVer } from "semver";
 import { logPlugin } from "./debug.ts";
-import getOptionSpecificExcludesFor from "./get-option-specific-excludes.ts";
 import {
   addProposalSyntaxPlugins,
   removeUnnecessaryItems,
@@ -318,6 +317,14 @@ export default declarePreset((api, opts: Options) => {
 
   const babelTargets = api.targets();
 
+  if (process.env.BABEL_8_BREAKING && ("loose" in opts || "spec" in opts)) {
+    throw new Error(
+      "@babel/preset-env: The 'loose' and 'spec' options have been removed, " +
+        "and you should configure granular compiler assumptions instead. See " +
+        "https://babeljs.io/assumptions for more information.",
+    );
+  }
+
   const {
     bugfixes,
     configPath,
@@ -326,16 +333,19 @@ export default declarePreset((api, opts: Options) => {
     forceAllTransforms,
     ignoreBrowserslistConfig,
     include: optionsInclude,
-    loose,
     modules: optionsModules,
     shippedProposals,
-    spec,
     targets: optionsTargets,
     useBuiltIns,
     corejs: { version: corejs, proposals },
     browserslistEnv,
   } = normalizeOptions(opts);
 
+  if (!process.env.BABEL_8_BREAKING) {
+    // eslint-disable-next-line no-var
+    var { loose, spec = false } = opts;
+  }
+
   let targets = babelTargets;
 
   if (
@@ -413,7 +423,9 @@ option \`forceAllTransforms: true\` instead.
     exclude.plugins,
     transformTargets,
     getSpecialModulesPluginNames(modules, shouldTransformDynamicImport),
-    getOptionSpecificExcludesFor({ loose }),
+    process.env.BABEL_8_BREAKING || !loose
+      ? undefined
+      : ["transform-typeof-symbol"],
     pluginSyntaxMap,
   );
   if (shippedProposals) {
@@ -456,9 +468,10 @@ option \`forceAllTransforms: true\` instead.
   const plugins = Array.from(pluginNames)
     .map(pluginName => {
       if (
-        pluginName === "transform-class-properties" ||
-        pluginName === "transform-private-methods" ||
-        pluginName === "transform-private-property-in-object"
+        !process.env.BABEL_8_BREAKING &&
+        (pluginName === "transform-class-properties" ||
+          pluginName === "transform-private-methods" ||
+          pluginName === "transform-private-property-in-object")
       ) {
         return [
           getPlugin(pluginName),
@@ -477,7 +490,9 @@ option \`forceAllTransforms: true\` instead.
       }
       return [
         getPlugin(pluginName),
-        { spec, loose, useBuiltIns: pluginUseBuiltIns },
+        process.env.BABEL_8_BREAKING
+          ? { useBuiltIns: pluginUseBuiltIns }
+          : { spec, loose, useBuiltIns: pluginUseBuiltIns },
       ];
     })
     .concat(polyfillPlugins);

packages/babel-preset-env/src/normalize-options.ts

@@ -271,6 +271,11 @@ export default function normalizeOptions(opts: Options) {
 
   checkDuplicateIncludeExcludes(include, exclude);
 
+  if (!process.env.BABEL_8_BREAKING) {
+    v.validateBooleanOption("loose", opts.loose);
+    v.validateBooleanOption("spec", opts.spec);
+  }
+
   return {
     bugfixes: v.validateBooleanOption(
       TopLevelOptions.bugfixes,
@@ -296,14 +301,12 @@ export default function normalizeOptions(opts: Options) {
       opts.ignoreBrowserslistConfig,
       false,
     ),
-    loose: v.validateBooleanOption(TopLevelOptions.loose, opts.loose),
     modules: validateModulesOption(opts.modules),
     shippedProposals: v.validateBooleanOption(
       TopLevelOptions.shippedProposals,
       opts.shippedProposals,
       false,
     ),
-    spec: v.validateBooleanOption(TopLevelOptions.spec, opts.spec, false),
     targets: normalizeTargets(opts.targets),
     useBuiltIns: useBuiltIns,
     browserslistEnv: v.validateStringOption(

packages/babel-preset-env/src/options.ts

@@ -7,15 +7,20 @@ export const TopLevelOptions = {
   forceAllTransforms: "forceAllTransforms",
   ignoreBrowserslistConfig: "ignoreBrowserslistConfig",
   include: "include",
-  loose: "loose",
   modules: "modules",
   shippedProposals: "shippedProposals",
-  spec: "spec",
   targets: "targets",
   useBuiltIns: "useBuiltIns",
   browserslistEnv: "browserslistEnv",
 } as const;
 
+if (!process.env.BABEL_8_BREAKING) {
+  Object.assign(TopLevelOptions, {
+    loose: "loose",
+    spec: "spec",
+  });
+}
+
 export const ModulesOption = {
   false: false,
   auto: "auto",

packages/babel-preset-env/src/types.d.ts

@@ -30,16 +30,18 @@ export type Options = {
   forceAllTransforms: boolean;
   ignoreBrowserslistConfig: boolean;
   include: PluginListOption;
-  loose: boolean;
   modules: ModuleOption;
   shippedProposals: boolean;
-  spec: boolean;
   targets: {
     uglify?: boolean;
     esmodules?: boolean;
   } & InputTargets;
   useBuiltIns: BuiltInsOption;
   browserslistEnv: string;
+
+  // TODO(Babel 8): Remove these options
+  loose: boolean;
+  spec: boolean;
 };
 
 // Babel

packages/babel-preset-env/test/fixtures/loose-class-features-precedence/methods-loose-preset-not-loose/options.json

@@ -1,4 +1,5 @@
 {
+  "BABEL_8_BREAKING": false,
   "validateLogs": true,
   "presets": [
     ["env", {

packages/babel-preset-env/test/fixtures/loose-class-features-precedence/preset-loose-no-plugins/options.json

@@ -1,4 +1,5 @@
 {
+  "BABEL_8_BREAKING": false,
   "validateLogs": true,
   "presets": [
     ["env", {

packages/babel-preset-env/test/fixtures/loose-class-features-precedence/preset-not-loose-no-plugins/options.json

@@ -1,4 +1,5 @@
 {
+  "BABEL_8_BREAKING": false,
   "validateLogs": true,
   "presets": [
     ["env", {

packages/babel-preset-env/test/fixtures/loose-class-features-precedence/properties-and-methods-loose-preset-not-loose/options.json

@@ -1,4 +1,5 @@
 {
+  "BABEL_8_BREAKING": false,
   "validateLogs": true,
   "presets": [
     ["env", {

packages/babel-preset-env/test/fixtures/loose-class-features-precedence/properties-and-methods-not-loose-preset-loose/options.json

@@ -1,4 +1,5 @@
 {
+  "BABEL_8_BREAKING": false,
   "validateLogs": true,
   "presets": [
     ["env", {

packages/babel-preset-env/test/fixtures/loose-class-features-precedence/properties-loose-preset-loose/options.json

@@ -1,4 +1,5 @@
 {
+  "BABEL_8_BREAKING": false,
   "validateLogs": true,
   "presets": [
     ["env", {

packages/babel-preset-env/test/fixtures/loose-class-features-precedence/properties-loose-preset-not-loose/options.json

@@ -1,4 +1,5 @@
 {
+  "BABEL_8_BREAKING": false,
   "validateLogs": true,
   "presets": [
     ["env", {

packages/babel-preset-env/test/fixtures/loose-class-features-precedence/properties-not-loose-preset-loose/options.json

@@ -1,4 +1,5 @@
 {
+  "BABEL_8_BREAKING": false,
   "validateLogs": true,
   "presets": [
     ["env", {

packages/babel-preset-env/test/fixtures/modules/modules-amd-loose/options.json → packages/babel-preset-env/test/fixtures/modules/modules-amd-loose-babel-7/options.json

@@ -1,4 +1,5 @@
 {
+  "BABEL_8_BREAKING": false,
   "presets": [
     [
       "env",

packages/babel-preset-env/test/fixtures/preset-options/removed-loose/input.js

@@ -0,0 +1 @@
+;

packages/babel-preset-env/test/fixtures/preset-options/removed-loose/options.json

@@ -0,0 +1,5 @@
+{
+  "BABEL_8_BREAKING": true,
+  "presets": [["env", { "loose": true }]],
+  "throws": "@babel/preset-env: The 'loose' and 'spec' options have been removed, and you should configure granular compiler assumptions instead. See https://babeljs.io/assumptions for more information."
+}

packages/babel-preset-env/test/fixtures/preset-options/removed-spec/input.js

@@ -0,0 +1 @@
+;