Add support for sourceType: commonjs option

FEATURE: The `sourceType` option can now be set to `"commonjs"` to have the parser treat the top level
scope as a function scope.

Author: ota-meshi

acorn-loose/src/statement.js

@@ -10,7 +10,7 @@ lp.parseTopLevel = function() {
   while (this.tok.type !== tt.eof) node.body.push(this.parseStatement())
   this.toks.adaptDirectivePrologue(node.body)
   this.last = this.tok
-  node.sourceType = this.options.sourceType
+  node.sourceType = this.options.sourceType === "commonjs" ? "script" : this.options.sourceType
   return this.finishNode(node, "Program")
 }
 

acorn/README.md

@@ -61,11 +61,12 @@ required):
   implemented through plugins.
 
 - **sourceType**: Indicate the mode the code should be parsed in. Can be
-  either `"script"` or `"module"`. This influences global strict mode
+  either `"script"`, `"module"` or `"commonjs"`. This influences global strict mode
   and parsing of `import` and `export` declarations.
 
   **NOTE**: If set to `"module"`, then static `import` / `export` syntax
-  will be valid, even if `ecmaVersion` is less than 6.
+  will be valid, even if `ecmaVersion` is less than 6. If set to `"commonjs"`,
+  it is the same as `"script"` except that the top-level scope behaves like a function.
 
 - **onInsertedSemicolon**: If given a callback, that callback will be
   called whenever a missing semicolon is inserted by the parser. The
@@ -97,7 +98,7 @@ required):
   for `ecmaVersion` 2022 and later, `false` for lower versions.
   Setting this option to `true` allows to have top-level `await`
   expressions. They are still not allowed in non-`async` functions,
-  though.
+  though. Setting this option to `true` is not allowed when `sourceType: "commonjs"`.
 
 - **allowSuperOutsideMethod**: By default, `super` outside a method
   raises an error. Set this to `true` to accept such code.

acorn/src/acorn.d.ts

@@ -614,10 +614,10 @@ export interface Options {
 
   /**
    * `sourceType` indicates the mode the code should be parsed in.
-   * Can be either `"script"` or `"module"`. This influences global
+   * Can be either `"script"`, `"module"` or `"commonjs"`. This influences global
    * strict mode and parsing of `import` and `export` declarations.
    */
-  sourceType?: "script" | "module"
+  sourceType?: "script" | "module" | "commonjs"
 
   /**
    * a callback that will be called when a semicolon is automatically inserted.

acorn/src/options.js

@@ -13,7 +13,7 @@ export const defaultOptions = {
   // for new syntax features.
   ecmaVersion: null,
   // `sourceType` indicates the mode the code should be parsed in.
-  // Can be either `"script"` or `"module"`. This influences global
+  // Can be either `"script"`, `"module"` or `"commonjs"`. This influences global
   // strict mode and parsing of `import` and `export` declarations.
   sourceType: "script",
   // `onInsertedSemicolon` can be a callback that will be called when
@@ -137,6 +137,9 @@ export function getOptions(opts) {
   if (isArray(options.onComment))
     options.onComment = pushComment(options, options.onComment)
 
+  if (options.sourceType === "commonjs" && options.allowAwaitOutsideFunction)
+    throw new Error("Cannot use allowAwaitOutsideFunction with sourceType: commonjs")
+
   return options
 }
 

acorn/src/state.js

@@ -83,7 +83,12 @@ export class Parser {
 
     // Scope tracking for duplicate variable names (see scope.js)
     this.scopeStack = []
-    this.enterScope(SCOPE_TOP)
+    this.enterScope(
+      this.options.sourceType === "commonjs"
+        // In commonjs, the top-level scope behaves like a function scope
+        ? SCOPE_FUNCTION
+        : SCOPE_TOP
+    )
 
     // For RegExp validation
     this.regexpState = null

acorn/src/statement.js

@@ -27,7 +27,7 @@ pp.parseTopLevel = function(node) {
       this.raiseRecoverable(this.undefinedExports[name].start, `Export '${name}' is not defined`)
   this.adaptDirectivePrologue(node.body)
   this.next()
-  node.sourceType = this.options.sourceType
+  node.sourceType = this.options.sourceType === "commonjs" ? "script" : this.options.sourceType
   return this.finishNode(node, "Program")
 }
 

test/driver.js

@@ -27,13 +27,13 @@ exports.runTests = function(config, callback) {
     try {
       var ast = parse(test.code, testOpts);
     } catch(e) {
-      if (!(e instanceof SyntaxError)) { console.log(e.stack); throw e; }
       if (test.error) {
         if (test.error.charAt(0) === "~" ? e.message.indexOf(test.error.slice(1)) > -1 : e.message === test.error)
           callback("ok", test.code);
         else
           callback("fail", test.code, "Expected error message: " + test.error + "\nGot error message: " + e.message);
       } else {
+        if (!(e instanceof SyntaxError)) { console.log(e.stack); throw e; }
         callback("error", test.code, e.message || e.toString());
       }
       continue

test/run.js

@@ -31,6 +31,7 @@
   require("./tests-module-string-names.js");
   require("./tests-import-attributes.js");
   require("./tests-using.js");
+  require("./tests-commonjs.js");
   var acorn = require("../acorn")
   var acorn_loose = require("../acorn-loose")
 
@@ -84,6 +85,28 @@
           return opts.loose !== false;
         }
       }
+    },
+
+    // Test whether the test for `sourceType: 'script'` produces the same result for `'commonjs'`.
+    'Normal with sourceType: commonjs': {
+      config: {
+        parse: (code, option) => acorn.parse(code, Object.assign({}, option, { sourceType: 'commonjs' })),
+        filter: function (test) {
+          var opts = test.options || {};
+          return opts.commonjs !== false && !opts.allowAwaitOutsideFunction && (!opts.sourceType || opts.sourceType === 'script');
+        }
+      }
+    },
+    'Loose with sourceType: commonjs': {
+      config: {
+        parse: (code, option) => acorn_loose.parse(code, Object.assign({}, option, { sourceType: 'commonjs' })),
+        loose: true,
+        filter: function (test) {
+          var opts = test.options || {};
+          if (opts.loose === false) return false;
+          return opts.commonjs !== false && !opts.allowAwaitOutsideFunction && (!opts.sourceType || opts.sourceType === 'script');
+        }
+      }
     }
   };
 

test/tests-commonjs.js

@@ -0,0 +1,97 @@
+if (typeof exports !== "undefined") {
+  var test = require("./driver.js").test
+  var testFail = require("./driver.js").testFail
+}
+
+// Top-level using declaration with commonjs
+test("using x = resource;", {
+  type: "Program",
+  body: [{
+    type: "VariableDeclaration",
+    declarations: [{
+      type: "VariableDeclarator",
+      id: {
+        type: "Identifier",
+        name: "x"
+      },
+      init: {
+        type: "Identifier",
+        name: "resource"
+      }
+    }],
+    kind: "using"
+  }],
+  sourceType: "script"
+}, {ecmaVersion: 17, sourceType: "commonjs"});
+
+// Top-level new.target with commonjs
+test("new.target", {
+  type: "Program",
+  body: [{
+    type: "ExpressionStatement",
+    expression: {
+      type: "MetaProperty",
+      meta: {type: "Identifier", name: "new"},
+      property: {type: "Identifier", name: "target"}
+    }
+  }],
+  sourceType: "script"
+}, {ecmaVersion: 6, sourceType: "commonjs"});
+
+// new.target at top-level scope with commonjs
+test("let y = () => new.target", {
+  type: "Program",
+  body: [{
+    type: "VariableDeclaration",
+    declarations: [{
+      type: "VariableDeclarator",
+      id: {
+        type: "Identifier",
+        name: "y"
+      },
+      init: {
+        type: "ArrowFunctionExpression",
+        body: {
+          type: "MetaProperty",
+          meta: {type: "Identifier", name: "new"},
+          property: {type: "Identifier", name: "target"}
+        },
+        params: []
+      }
+    }],
+    kind: "let"
+  }],
+  sourceType: "script"
+}, {ecmaVersion: 6, sourceType: "commonjs"});
+
+// Top-level return statement with commonjs
+test("return {} / 2", {
+  type: "Program",
+  body: [{
+    type: "ReturnStatement",
+    argument: {
+      type: "BinaryExpression",
+      left: {
+        type: "ObjectExpression",
+        properties: []
+      },
+      right: {
+        type: "Literal",
+        value: 2
+      },
+      operator: "/"
+    }
+  }],
+  sourceType: "script"
+}, {sourceType: "commonjs"});
+
+// Illegal return statement with commonjs
+testFail(`class X { static { return; } }`, "'return' outside of function (1:19)", {ecmaVersion: 13, sourceType: "commonjs"});
+
+// Top-level await using declaration with commonjs
+testFail("await using x = resource;", "Await using cannot appear outside of async function (1:0)", {ecmaVersion: 17, sourceType: "commonjs"});
+
+// Disallowing allowAwaitOutsideFunction with commonjs
+testFail("await 1", "Cannot use allowAwaitOutsideFunction with sourceType: commonjs", {allowAwaitOutsideFunction: true, sourceType: "commonjs"});
+testFail("x", "Cannot use allowAwaitOutsideFunction with sourceType: commonjs", {allowAwaitOutsideFunction: true, sourceType: "commonjs"});
+test("x", {}, {allowAwaitOutsideFunction: false, sourceType: "commonjs"});

test/tests-harmony.js

@@ -14873,9 +14873,9 @@ test("function foo() { new.target; }", {
 }, {ecmaVersion: 6});
 
 testFail("new.prop", "The only valid meta property for new is 'new.target' (1:4)", {ecmaVersion: 6});
-testFail("new.target", "'new.target' can only be used in functions and class static block (1:0)", {ecmaVersion: 6});
+testFail("new.target", "'new.target' can only be used in functions and class static block (1:0)", {ecmaVersion: 6, commonjs: false});
 test("function x() { return () => new.target }", {}, {ecmaVersion: 6});
-testFail("let y = () => new.target", "'new.target' can only be used in functions and class static block (1:14)", {ecmaVersion: 6});
+testFail("let y = () => new.target", "'new.target' can only be used in functions and class static block (1:14)", {ecmaVersion: 6, commonjs: false});
 
 test("export default function foo() {} false", {
   body: [