feat(babel): overrideContext option (#1342)

.changeset/lovely-moles-laugh.md

@@ -0,0 +1,5 @@
+---
+'@linaria/babel-preset': patch
+---
+
+The new option, 'overrideContext,' allows the extension of the module evaluation context.

docs/CONFIGURATION.md

@@ -175,6 +175,20 @@ module.exports = {
   - `unit` - the unit.
   - `valueSlug` - the value slug.
 
+
+- `overrideContext: (context: Partial<vm.Context>, filename: string) => Partial<vm.Context>`
+
+  A custom function to override the context used to evaluate modules. This can be used to add custom globals or override the default ones.
+    
+  ```js
+  module.exports = {
+    overrideContext: (context, filename) => ({
+      ...context,
+      HighLevelAPI: () => "I'm a high level API",
+    }),
+  };
+  ```
+
 - `rules: EvalRule[]`
 
   The set of rules that defines how the matched files will be transformed during the evaluation.

packages/babel/src/module.ts

@@ -250,7 +250,7 @@ class Module {
       evaluatedCreated = true;
     }
 
-    const source = entrypoint.transformedCode;
+    const { transformedCode: source, pluginOptions } = entrypoint;
 
     if (!source) {
       this.debug(`evaluate`, 'there is nothing to evaluate');
@@ -277,14 +277,15 @@ class Module {
 
     const { context, teardown } = createVmContext(
       filename,
-      entrypoint.pluginOptions.features,
+      pluginOptions.features,
       {
         module: this,
         exports: entrypoint.exports,
         require: this.require,
         __linaria_dynamic_import: async (id: string) => this.require(id),
         __dirname: path.dirname(filename),
-      }
+      },
+      pluginOptions.overrideContext
     );
 
     try {

packages/babel/src/vm/createVmContext.ts

@@ -2,7 +2,7 @@ import * as vm from 'vm';
 
 import type { Window } from 'happy-dom';
 
-import type { FeatureFlags } from '@linaria/utils';
+import type { FeatureFlags, StrictOptions } from '@linaria/utils';
 import { isFeatureEnabled } from '@linaria/utils';
 
 import * as process from './process';
@@ -72,17 +72,24 @@ function createNothing() {
 export function createVmContext(
   filename: string,
   features: FeatureFlags<'happyDOM'>,
-  additionalContext: Partial<vm.Context>
+  additionalContext: Partial<vm.Context>,
+  overrideContext: StrictOptions['overrideContext'] = (i) => i
 ) {
   const isHappyDOMEnabled = isFeatureEnabled(features, 'happyDOM', filename);
 
   const { teardown, window } = isHappyDOMEnabled
     ? createHappyDOMWindow()
     : createNothing();
-  const baseContext = createBaseContext(window, {
-    __filename: filename,
-    ...additionalContext,
-  });
+  const baseContext = createBaseContext(
+    window,
+    overrideContext(
+      {
+        __filename: filename,
+        ...additionalContext,
+      },
+      filename
+    )
+  );
 
   const context = vm.createContext(baseContext);
 

packages/testkit/src/module.test.ts

@@ -37,18 +37,22 @@ const createServices = (partial: Partial<Services>): Services => {
 const filename = path.resolve(__dirname, './__fixtures__/test.js');
 
 const options: StrictOptions = {
+  babelOptions: {},
   displayName: false,
   evaluate: true,
   extensions: ['.cjs', '.js', '.jsx', '.ts', '.tsx'],
-  rules: [],
-  babelOptions: {},
   features: {
     dangerousCodeRemover: true,
     globalCache: true,
     happyDOM: true,
     softErrors: false,
   },
   highPriorityPlugins: [],
+  overrideContext: (context) => ({
+    ...context,
+    HighLevelAPI: () => "I'm a high level API",
+  }),
+  rules: [],
 };
 
 const createEntrypoint = (
@@ -296,6 +300,16 @@ it("doesn't have access to the process object", () => {
   expect(() => mod.evaluate()).toThrow('process.abort is not a function');
 });
 
+it('has access to a overridden context', () => {
+  const { mod } = create`
+    module.exports = HighLevelAPI();
+  `;
+
+  safeEvaluate(mod);
+
+  expect(mod.exports).toBe("I'm a high level API");
+});
+
 it('has access to NODE_ENV', () => {
   const { mod } = create`
     module.exports = process.env.NODE_ENV;

packages/utils/src/options/types.ts

@@ -1,3 +1,5 @@
+import type { Context as VmContext } from 'vm';
+
 import type { TransformOptions } from '@babel/core';
 import type { File } from '@babel/types';
 
@@ -68,6 +70,10 @@ export type StrictOptions = {
   features: FeatureFlags;
   highPriorityPlugins: string[];
   ignore?: RegExp;
+  overrideContext?: (
+    context: Partial<VmContext>,
+    filename: string
+  ) => Partial<VmContext>;
   rules: EvalRule[];
   tagResolver?: (source: string, tag: string) => string | null;
   variableNameConfig?: 'var' | 'dashes' | 'raw';