Add support for import.meta

Author: mysticatea

acorn-loose/src/expression.js

@@ -310,10 +310,13 @@ lp.parseExprAtom = function() {
 
 lp.parseExprImport = function() {
   const node = this.startNode()
-  this.next() // skip `import`
+  const meta = this.parseIdent(true)
   switch (this.tok.type) {
   case tt.parenL:
     return this.parseDynamicImport(node)
+  case tt.dot:
+    node.meta = meta
+    return this.parseImportMeta(node)
   default:
     node.name = "import"
     return this.finishNode(node, "Identifier")
@@ -325,6 +328,12 @@ lp.parseDynamicImport = function(node) {
   return this.finishNode(node, "ImportExpression")
 }
 
+lp.parseImportMeta = function(node) {
+  this.next() // skip '.'
+  node.property = this.parseIdent(true)
+  return this.finishNode(node, "MetaProperty")
+}
+
 lp.parseNew = function() {
   let node = this.startNode(), startIndent = this.curIndent, line = this.curLineStart
   let meta = this.parseIdent(true)

acorn-loose/src/statement.js

@@ -176,10 +176,13 @@ lp.parseStatement = function() {
     return this.parseClass(true)
 
   case tt._import:
-    if (this.options.ecmaVersion > 10 && this.lookAhead(1).type === tt.parenL) {
-      node.expression = this.parseExpression()
-      this.semicolon()
-      return this.finishNode(node, "ExpressionStatement")
+    if (this.options.ecmaVersion > 10) {
+      const nextType = this.lookAhead(1).type
+      if (nextType === tt.parenL || nextType === tt.dot) {
+        node.expression = this.parseExpression()
+        this.semicolon()
+        return this.finishNode(node, "ExpressionStatement")
+      }
     }
 
     return this.parseImport()

acorn/src/expression.js

@@ -427,10 +427,18 @@ pp.parseExprAtom = function(refDestructuringErrors) {
 
 pp.parseExprImport = function() {
   const node = this.startNode()
-  this.next() // skip `import`
+
+  // Consume `import` as an identifier for `import.meta`.
+  // Because `this.parseIdent(true)` doesn't check escape sequences, it needs the check of `this.containsEsc`.
+  if (this.containsEsc) this.raiseRecoverable(this.start, "Escape sequence in keyword import")
+  const meta = this.parseIdent(true)
+
   switch (this.type) {
   case tt.parenL:
     return this.parseDynamicImport(node)
+  case tt.dot:
+    node.meta = meta
+    return this.parseImportMeta(node)
   default:
     this.unexpected()
   }
@@ -455,6 +463,22 @@ pp.parseDynamicImport = function(node) {
   return this.finishNode(node, "ImportExpression")
 }
 
+pp.parseImportMeta = function(node) {
+  this.next() // skip `.`
+
+  const containsEsc = this.containsEsc
+  node.property = this.parseIdent(true)
+
+  if (node.property.name !== "meta")
+    this.raiseRecoverable(node.property.start, "The only valid meta property for import is 'import.meta'")
+  if (containsEsc)
+    this.raiseRecoverable(node.start, "'import.meta' must not contain escaped characters")
+  if (this.options.sourceType !== "module")
+    this.raiseRecoverable(node.start, "Cannot use 'import.meta' outside a module")
+
+  return this.finishNode(node, "MetaProperty")
+}
+
 pp.parseLiteral = function(value) {
   let node = this.startNode()
   node.value = value
@@ -557,10 +581,12 @@ pp.parseNew = function() {
     node.meta = meta
     let containsEsc = this.containsEsc
     node.property = this.parseIdent(true)
-    if (node.property.name !== "target" || containsEsc)
-      this.raiseRecoverable(node.property.start, "The only valid meta property for new is new.target")
+    if (node.property.name !== "target")
+      this.raiseRecoverable(node.property.start, "The only valid meta property for new is 'new.target'")
+    if (containsEsc)
+      this.raiseRecoverable(node.start, "'new.target' must not contain escaped characters")
     if (!this.inNonArrowFunction())
-      this.raiseRecoverable(node.start, "new.target can only be used in functions")
+      this.raiseRecoverable(node.start, "'new.target' can only be used in functions")
     return this.finishNode(node, "MetaProperty")
   }
   let startPos = this.start, startLoc = this.startLoc, isImport = this.type === tt._import

acorn/src/statement.js

@@ -122,7 +122,7 @@ pp.parseStatement = function(context, topLevel, exports) {
       skipWhiteSpace.lastIndex = this.pos
       let skip = skipWhiteSpace.exec(this.input)
       let next = this.pos + skip[0].length, nextCh = this.input.charCodeAt(next)
-      if (nextCh === 40) // '('
+      if (nextCh === 40 || nextCh === 46) // '(' or '.'
         return this.parseExpressionStatement(node, this.parseExpression())
     }
 

bin/run_test262.js

@@ -11,7 +11,6 @@ const unsupportedFeatures = [
   "class-static-fields-public",
   "class-static-methods-private",
   "coalesce-expression",
-  "import.meta",
   "numeric-separator-literal",
   "optional-chaining",
   "top-level-await"

test/run.js

@@ -18,6 +18,7 @@
   require("./tests-bigint.js");
   require("./tests-dynamic-import.js");
   require("./tests-export-all-as-ns-from-source.js");
+  require("./tests-import-meta.js");
   var acorn = require("../acorn")
   var acorn_loose = require("../acorn-loose")
 

test/tests-dynamic-import.js

@@ -204,7 +204,7 @@ test(
   { ecmaVersion: 11 }
 );
 
-testFail('function failsParse() { return import.then(); }', 'Unexpected token (1:37)', {
+testFail('function failsParse() { return import.then(); }', 'The only valid meta property for import is \'import.meta\' (1:38)', {
   ecmaVersion: 11,
   loose: false
 });

test/tests-harmony.js

@@ -14781,10 +14781,10 @@ test("function foo() { new.target; }", {
   sourceType: "script"
 }, {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 (1:0)", {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 (1:0)", {ecmaVersion: 6});
 test("function x() { return () => new.target }", {}, {ecmaVersion: 6});
-testFail("let y = () => new.target", "new.target can only be used in functions (1:14)", {ecmaVersion: 6});
+testFail("let y = () => new.target", "'new.target' can only be used in functions (1:14)", {ecmaVersion: 6});
 
 test("export default function foo() {} false", {
   body: [

test/tests-import-meta.js

@@ -0,0 +1,97 @@
+// Tests for ECMAScript 2020 `import.meta`
+
+if (typeof exports != 'undefined') {
+  var test = require('./driver.js').test;
+  var testFail = require('./driver.js').testFail;
+}
+
+test(
+  "import.meta",
+  {
+    "type": "Program",
+    "start": 0,
+    "end": 11,
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start": 0,
+        "end": 11,
+        "expression": {
+          "type": "MetaProperty",
+          "start": 0,
+          "end": 11,
+          "meta": {
+            "type": "Identifier",
+            "start": 0,
+            "end": 6,
+            "name": "import"
+          },
+          "property": {
+            "type": "Identifier",
+            "start": 7,
+            "end": 11,
+            "name": "meta"
+          }
+        }
+      }
+    ],
+    "sourceType": "module"
+  },
+  { ecmaVersion: 11, sourceType: "module" }
+);
+
+test(
+  "import.meta.url",
+  {
+    "type": "Program",
+    "start": 0,
+    "end": 15,
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start": 0,
+        "end": 15,
+        "expression": {
+          "type": "MemberExpression",
+          "start": 0,
+          "end": 15,
+          "object": {
+            "type": "MetaProperty",
+            "start": 0,
+            "end": 11,
+            "meta": {
+              "type": "Identifier",
+              "start": 0,
+              "end": 6,
+              "name": "import"
+            },
+            "property": {
+              "type": "Identifier",
+              "start": 7,
+              "end": 11,
+              "name": "meta"
+            }
+          },
+          "property": {
+            "type": "Identifier",
+            "start": 12,
+            "end": 15,
+            "name": "url"
+          },
+          "computed": false
+        }
+      }
+    ],
+    "sourceType": "module"
+  },
+  { ecmaVersion: 11, sourceType: "module" }
+);
+
+testFail("import.meta", "Unexpected token (1:6)", { ecmaVersion: 10, sourceType: "module" });
+testFail("import.meta", "Cannot use 'import.meta' outside a module (1:0)", { ecmaVersion: 11, sourceType: "script" });
+testFail("import['meta']", "Unexpected token (1:6)", { ecmaVersion: 11, sourceType: "module" });
+testFail("a = import['meta']", "Unexpected token (1:10)", { ecmaVersion: 11, sourceType: "module" });
+testFail("import.target", "The only valid meta property for import is 'import.meta' (1:7)", { ecmaVersion: 11, sourceType: "module" });
+testFail("new.meta", "The only valid meta property for new is 'new.target' (1:4)", { ecmaVersion: 11, sourceType: "module" });
+testFail("im\\u0070ort.meta", "Escape sequence in keyword import (1:0)", { ecmaVersion: 11, sourceType: "module" });
+testFail("import.\\u006d\\u0065\\u0074\\u0061", "'import.meta' must not contain escaped characters (1:0)", { ecmaVersion: 11, sourceType: "module" });

test/tests.js

@@ -29428,7 +29428,7 @@ test("(\\u0061sync ())", {
 }, {ecmaVersion: 8})
 testFail("({ \\u0061sync x() { await x } })", "Unexpected token (1:14)", {ecmaVersion: 8})
 testFail("for (x \\u006ff y) {}", "Unexpected token (1:7)", {ecmaVersion: 6})
-testFail("function x () { new.ta\\u0072get }", "The only valid meta property for new is new.target (1:20)", {ecmaVersion: 6})
+testFail("function x () { new.ta\\u0072get }", "'new.target' must not contain escaped characters (1:16)", {ecmaVersion: 6})
 testFail("class X { st\\u0061tic y() {} }", "Unexpected token (1:22)", {ecmaVersion: 6})
 
 testFail("(x=1)=2", "Parenthesized pattern (1:0)")