Parse import reflection (#14926)

Co-authored-by: Nicolò Ribaudo <nicolo.ribaudo@gmail.com>

babel.config.js

@@ -772,7 +772,7 @@ function getTokenTypesMapping() {
       );
     }
 
-    const tokenTypesDefinition = typesDeclaration.init.properties;
+    const tokenTypesDefinition = typesDeclaration.init.expression.properties;
     for (let i = 0; i < tokenTypesDefinition.length; i++) {
       tokenTypesMapping.set(tokenTypesDefinition[i].key.name, i);
     }

packages/babel-generator/src/generators/modules.ts

@@ -201,8 +201,13 @@ export function ImportDeclaration(this: Printer, node: t.ImportDeclaration) {
 
   const isTypeKind = node.importKind === "type" || node.importKind === "typeof";
   if (isTypeKind) {
+    this.printInnerComments(node, false);
     this.word(node.importKind);
     this.space();
+  } else if (node.module) {
+    this.printInnerComments(node, false);
+    this.word("module");
+    this.space();
   }
 
   const specifiers = node.specifiers.slice(0);

packages/babel-generator/test/fixtures/comments/import-reflection-inner-comment/input.mjs

@@ -0,0 +1 @@
+/* 0 */import /* 1 */module /* 2 */from /* 3 */from /* 4 */"./module.wasm"/* 5 */;

packages/babel-generator/test/fixtures/comments/import-reflection-inner-comment/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": ["importReflection"]
+}

packages/babel-generator/test/fixtures/comments/import-reflection-inner-comment/output.js

@@ -0,0 +1 @@
+/* 0 */import /* 1 */module /* 2 */from /* 3 */ from /* 4 */"./module.wasm" /* 5 */;

packages/babel-generator/test/fixtures/import-reflection/basic/input.js

@@ -0,0 +1 @@
+import module foo from "./module.wasm";

packages/babel-generator/test/fixtures/import-reflection/basic/output.js

@@ -0,0 +1 @@
+import module foo from "./module.wasm";

packages/babel-generator/test/fixtures/import-reflection/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": ["importReflection"]
+}

packages/babel-parser/data/schema.json

@@ -142,6 +142,7 @@
               "functionSent",
               "importAssertions",
               "importMeta",
+              "importReflection",
               "jsx",
               "logicalAssignment",
               "moduleStringNames",

packages/babel-parser/src/index.ts

@@ -80,7 +80,9 @@ function generateExportedTokenTypes(
   internalTokenTypes: InternalTokenTypes,
 ): Record<string, ExportedTokenType> {
   const tokenTypes: Record<string, ExportedTokenType> = {};
-  for (const typeName of Object.keys(internalTokenTypes)) {
+  for (const typeName of Object.keys(
+    internalTokenTypes,
+  ) as (keyof InternalTokenTypes)[]) {
     tokenTypes[typeName] = getExportedToken(internalTokenTypes[typeName]);
   }
   return tokenTypes;

packages/babel-parser/src/parse-error/standard-errors.ts

@@ -117,6 +117,9 @@ export default {
   ImportCallSpreadArgument: "`...` is not allowed in `import()`.",
   ImportJSONBindingNotDefault:
     "A JSON module can only be imported with `default`.",
+  ImportReflectionHasAssertion: "`import module x` cannot have assertions.",
+  ImportReflectionNotBinding:
+    'Only `import module x from "./module"` is valid.',
   IncompatibleRegExpUVFlags:
     "The 'u' and 'v' regular expression flags cannot be enabled at the same time.",
   InvalidBigIntLiteral: "Invalid BigIntLiteral.",

packages/babel-parser/src/parser/statement.ts

@@ -2654,6 +2654,24 @@ export default abstract class StatementParser extends ExpressionParser {
     return false;
   }
 
+  checkImportReflection(node: Undone<N.ImportDeclaration>) {
+    if (node.module) {
+      if (
+        node.specifiers.length !== 1 ||
+        node.specifiers[0].type !== "ImportDefaultSpecifier"
+      ) {
+        this.raise(Errors.ImportReflectionNotBinding, {
+          at: node.specifiers[0].loc.start,
+        });
+      }
+      if (node.assertions?.length > 0) {
+        this.raise(Errors.ImportReflectionHasAssertion, {
+          at: node.specifiers[0].loc.start,
+        });
+      }
+    }
+  }
+
   checkJSONModuleImport(
     node: Undone<
       N.ExportAllDeclaration | N.ExportNamedDeclaration | N.ImportDeclaration
@@ -2687,13 +2705,47 @@ export default abstract class StatementParser extends ExpressionParser {
     }
   }
 
+  parseMaybeImportReflection(node: Undone<N.ImportDeclaration>) {
+    let isImportReflection = false;
+    if (this.isContextual(tt._module)) {
+      const lookahead = this.lookahead();
+      if (tokenIsIdentifier(lookahead.type)) {
+        if (lookahead.type !== tt._from) {
+          // import module x
+          isImportReflection = true;
+        } else {
+          const nextNextTokenFirstChar = this.input.charCodeAt(
+            this.nextTokenStartSince(lookahead.end),
+          );
+          if (nextNextTokenFirstChar === charCodes.lowercaseF) {
+            // import module from from ...
+            isImportReflection = true;
+          }
+        }
+      } else {
+        // import module { x } ...
+        // This is invalid, we will continue parsing and throw
+        // a recoverable error later
+        isImportReflection = true;
+      }
+    }
+    if (isImportReflection) {
+      this.expectPlugin("importReflection");
+      this.next(); // eat tt._module;
+      node.module = true;
+    } else if (this.hasPlugin("importReflection")) {
+      node.module = false;
+    }
+  }
+
   // Parses import declaration.
   // https://tc39.es/ecma262/#prod-ImportDeclaration
 
   parseImport(this: Parser, node: Undone<N.ImportDeclaration>): N.AnyImport {
     // import '...'
     node.specifiers = [];
     if (!this.match(tt.string)) {
+      this.parseMaybeImportReflection(node);
       // check if we have a default import like
       // import React from "react";
       const hasDefault = this.maybeParseDefaultImportSpecifier(node);
@@ -2726,6 +2778,7 @@ export default abstract class StatementParser extends ExpressionParser {
         node.attributes = attributes;
       }
     }
+    this.checkImportReflection(node);
     this.checkJSONModuleImport(node);
 
     this.semicolon();

packages/babel-parser/src/plugins/flow/index.ts

@@ -164,6 +164,8 @@ const FlowErrors = ParseErrorEnum`flow`({
   }) =>
     `String enum members need to consistently either all use initializers, or use no initializers, in enum \`${enumName}\`.`,
   GetterMayNotHaveThisParam: "A getter cannot have a `this` parameter.",
+  ImportReflectionHasImportType:
+    "An `import module` declaration can not use `type` or `typeof` keyword.",
   ImportTypeShorthandOnlyInPureImport:
     "The `type` and `typeof` keywords on named imports can only be used on regular `import` statements. It cannot be used with `import type` or `import typeof` statements.",
   InexactInsideExact:
@@ -2718,6 +2720,15 @@ export default (superClass: typeof Parser) =>
       return isMaybeDefaultImport(this.state.type);
     }
 
+    checkImportReflection(node: Undone<N.ImportDeclaration>) {
+      super.checkImportReflection(node);
+      if (node.module && node.importKind !== "value") {
+        this.raise(FlowErrors.ImportReflectionHasImportType, {
+          at: node.specifiers[0].loc.start,
+        });
+      }
+    }
+
     parseImportSpecifierLocal<
       T extends
         | N.ImportSpecifier

packages/babel-parser/src/plugins/typescript/index.ts

@@ -121,6 +121,8 @@ const TSErrors = ParseErrorEnum`typescript`({
   ExpectedAmbientAfterExportDeclare:
     "'export declare' must be followed by an ambient declaration.",
   ImportAliasHasImportType: "An import alias can not use 'import type'.",
+  ImportReflectionHasImportType:
+    "An `import module` declaration can not use `type` modifier",
   IncompatibleModifiers: ({
     modifiers,
   }: {
@@ -2603,6 +2605,15 @@ export default (superClass: ClassWithMixin<typeof Parser, IJSXParserMixin>) =>
       }
     }
 
+    checkImportReflection(node: Undone<N.ImportDeclaration>) {
+      super.checkImportReflection(node);
+      if (node.module && node.importKind !== "value") {
+        this.raise(TSErrors.ImportReflectionHasImportType, {
+          at: node.specifiers[0].loc.start,
+        });
+      }
+    }
+
     /*
     Don't bother doing this check in TypeScript code because:
     1. We may have a nested export statement with the same name:

packages/babel-parser/src/tokenizer/types.ts

@@ -134,11 +134,9 @@ function createKeywordLike(
 // For performance the token type helpers depend on the following declarations order.
 // When adding new token types, please also check if the token helpers need update.
 
-export type InternalTokenTypes = {
-  [name: string]: TokenType;
-};
+export type InternalTokenTypes = typeof tt;
 
-export const tt: InternalTokenTypes = {
+export const tt = {
   // Punctuation token types.
   bracketL: createToken("[", { beforeExpr, startsExpr }),
   bracketHashL: createToken("#[", { beforeExpr, startsExpr }),
@@ -346,7 +344,7 @@ export const tt: InternalTokenTypes = {
 
   // placeholder plugin
   placeholder: createToken("%%", { startsExpr: true }),
-};
+} as const;
 
 export function tokenIsIdentifier(token: TokenType): boolean {
   return token >= tt._as && token <= tt.name;

packages/babel-parser/src/types.d.ts

@@ -922,6 +922,7 @@ export interface ImportDeclaration extends NodeBase {
   source: Literal;
   importKind?: "type" | "typeof" | "value"; // TODO: Not in spec,
   assertions?: ImportAttribute[];
+  module?: boolean;
 }
 
 export interface ImportSpecifier extends ModuleSpecifier {

packages/babel-parser/src/typings.d.ts

@@ -22,6 +22,7 @@ export type Plugin =
   | "jsx"
   | "logicalAssignment"
   | "importAssertions"
+  | "importReflection"
   | "moduleBlocks"
   | "moduleStringNames"
   | "nullishCoalescingOperator"

packages/babel-parser/test/fixtures/experimental/_no-plugin/import-reflection/input.mjs

@@ -0,0 +1 @@
+import module foo from "./module.wasm";

packages/babel-parser/test/fixtures/experimental/_no-plugin/import-reflection/options.json

@@ -0,0 +1,3 @@
+{
+  "throws": "This experimental syntax requires enabling the parser plugin: \"importReflection\". (1:7)"
+}

packages/babel-parser/test/fixtures/experimental/import-reflection/invalid-assertions/input.mjs

@@ -0,0 +1 @@
+import module foo from "./module.json" assert { type: "json" }

packages/babel-parser/test/fixtures/experimental/import-reflection/invalid-assertions/options.json

@@ -0,0 +1,4 @@
+{
+  "plugins": ["importReflection", "importAssertions"],
+  "sourceType": "module"
+}

packages/babel-parser/test/fixtures/experimental/import-reflection/invalid-assertions/output.json

@@ -0,0 +1,61 @@
+{
+  "type": "File",
+  "start":0,"end":62,"loc":{"start":{"line":1,"column":0,"index":0},"end":{"line":1,"column":62,"index":62}},
+  "errors": [
+    "SyntaxError: `import module x` cannot have assertions. (1:14)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":62,"loc":{"start":{"line":1,"column":0,"index":0},"end":{"line":1,"column":62,"index":62}},
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ImportDeclaration",
+        "start":0,"end":62,"loc":{"start":{"line":1,"column":0,"index":0},"end":{"line":1,"column":62,"index":62}},
+        "specifiers": [
+          {
+            "type": "ImportDefaultSpecifier",
+            "start":14,"end":17,"loc":{"start":{"line":1,"column":14,"index":14},"end":{"line":1,"column":17,"index":17}},
+            "local": {
+              "type": "Identifier",
+              "start":14,"end":17,"loc":{"start":{"line":1,"column":14,"index":14},"end":{"line":1,"column":17,"index":17},"identifierName":"foo"},
+              "name": "foo"
+            }
+          }
+        ],
+        "module": true,
+        "source": {
+          "type": "StringLiteral",
+          "start":23,"end":38,"loc":{"start":{"line":1,"column":23,"index":23},"end":{"line":1,"column":38,"index":38}},
+          "extra": {
+            "rawValue": "./module.json",
+            "raw": "\"./module.json\""
+          },
+          "value": "./module.json"
+        },
+        "assertions": [
+          {
+            "type": "ImportAttribute",
+            "start":48,"end":60,"loc":{"start":{"line":1,"column":48,"index":48},"end":{"line":1,"column":60,"index":60}},
+            "key": {
+              "type": "Identifier",
+              "start":48,"end":52,"loc":{"start":{"line":1,"column":48,"index":48},"end":{"line":1,"column":52,"index":52},"identifierName":"type"},
+              "name": "type"
+            },
+            "value": {
+              "type": "StringLiteral",
+              "start":54,"end":60,"loc":{"start":{"line":1,"column":54,"index":54},"end":{"line":1,"column":60,"index":60}},
+              "extra": {
+                "rawValue": "json",
+                "raw": "\"json\""
+              },
+              "value": "json"
+            }
+          }
+        ]
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/import-reflection/invalid-default-named-import/input.mjs

@@ -0,0 +1 @@
+import module foo, {bar} from "./module.wasm";

packages/babel-parser/test/fixtures/experimental/import-reflection/invalid-default-named-import/output.json

@@ -0,0 +1,55 @@
+{
+  "type": "File",
+  "start":0,"end":46,"loc":{"start":{"line":1,"column":0,"index":0},"end":{"line":1,"column":46,"index":46}},
+  "errors": [
+    "SyntaxError: Only `import module x from \"./module\"` is valid. (1:14)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":46,"loc":{"start":{"line":1,"column":0,"index":0},"end":{"line":1,"column":46,"index":46}},
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ImportDeclaration",
+        "start":0,"end":46,"loc":{"start":{"line":1,"column":0,"index":0},"end":{"line":1,"column":46,"index":46}},
+        "specifiers": [
+          {
+            "type": "ImportDefaultSpecifier",
+            "start":14,"end":17,"loc":{"start":{"line":1,"column":14,"index":14},"end":{"line":1,"column":17,"index":17}},
+            "local": {
+              "type": "Identifier",
+              "start":14,"end":17,"loc":{"start":{"line":1,"column":14,"index":14},"end":{"line":1,"column":17,"index":17},"identifierName":"foo"},
+              "name": "foo"
+            }
+          },
+          {
+            "type": "ImportSpecifier",
+            "start":20,"end":23,"loc":{"start":{"line":1,"column":20,"index":20},"end":{"line":1,"column":23,"index":23}},
+            "imported": {
+              "type": "Identifier",
+              "start":20,"end":23,"loc":{"start":{"line":1,"column":20,"index":20},"end":{"line":1,"column":23,"index":23},"identifierName":"bar"},
+              "name": "bar"
+            },
+            "local": {
+              "type": "Identifier",
+              "start":20,"end":23,"loc":{"start":{"line":1,"column":20,"index":20},"end":{"line":1,"column":23,"index":23},"identifierName":"bar"},
+              "name": "bar"
+            }
+          }
+        ],
+        "module": true,
+        "source": {
+          "type": "StringLiteral",
+          "start":30,"end":45,"loc":{"start":{"line":1,"column":30,"index":30},"end":{"line":1,"column":45,"index":45}},
+          "extra": {
+            "rawValue": "./module.wasm",
+            "raw": "\"./module.wasm\""
+          },
+          "value": "./module.wasm"
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/import-reflection/invalid-export-from/input.mjs

@@ -0,0 +1 @@
+export module x from "./module.wasm";

packages/babel-parser/test/fixtures/experimental/import-reflection/invalid-export-from/options.json

@@ -0,0 +1,8 @@
+{
+  "plugins": [
+    "importReflection",
+    "exportDefaultFrom"
+  ],
+  "sourceType": "module",
+  "throws": "Unexpected token, expected \"{\" (1:7)"
+}

packages/babel-parser/test/fixtures/experimental/import-reflection/invalid-flow-type-import-1/input.mjs

@@ -0,0 +1 @@
+import type module foo from "./module.wasm";

packages/babel-parser/test/fixtures/experimental/import-reflection/invalid-flow-type-import-1/options.json

@@ -0,0 +1,8 @@
+{
+  "plugins": [
+    "importReflection",
+    "flow"
+  ],
+  "sourceType": "module",
+  "throws": "Unexpected token, expected \"from\" (1:19)"
+}

packages/babel-parser/test/fixtures/experimental/import-reflection/invalid-flow-type-import-2/input.mjs

@@ -0,0 +1 @@
+import module type foo from "./module.wasm";