Refactor import and export parsing (#9326)

* [parser] Refactor import parsing

* [parser] Refactor export parsing

* Fix types

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

@@ -1470,35 +1470,109 @@ export default class StatementParser extends ExpressionParser {
 
   // Parses module export declaration.
 
-  // TODO: better type. Node is an N.AnyExport.
-  parseExport(node: N.Node): N.Node {
-    // export * from '...'
-    if (this.shouldParseExportStar()) {
-      this.parseExportStar(node);
-      if (node.type === "ExportAllDeclaration") return node;
-    } else if (this.isExportDefaultSpecifier()) {
-      this.expectPlugin("exportDefaultFrom");
-      const specifier = this.startNode();
-      specifier.exported = this.parseIdentifier(true);
-      const specifiers = [this.finishNode(specifier, "ExportDefaultSpecifier")];
-      node.specifiers = specifiers;
-      if (this.match(tt.comma) && this.lookahead().type === tt.star) {
-        this.expect(tt.comma);
-        const specifier = this.startNode();
-        this.expect(tt.star);
-        this.expectContextual("as");
-        specifier.exported = this.parseIdentifier();
-        specifiers.push(this.finishNode(specifier, "ExportNamespaceSpecifier"));
-      } else {
-        this.parseExportSpecifiersMaybe(node);
-      }
+  parseExport(node: N.Node): N.AnyExport {
+    const hasDefault = this.maybeParseExportDefaultSpecifier(node);
+    const parseAfterDefault = !hasDefault || this.eat(tt.comma);
+    const hasStar = parseAfterDefault && this.eatExportStar(node);
+    const hasNamespace =
+      hasStar && this.maybeParseExportNamespaceSpecifier(node);
+    const parseAfterNamespace =
+      parseAfterDefault && (!hasNamespace || this.eat(tt.comma));
+    const isFromRequired = hasDefault || hasStar;
+
+    if (hasStar && !hasNamespace) {
+      if (hasDefault) this.unexpected();
       this.parseExportFrom(node, true);
-    } else if (this.eat(tt._default)) {
+
+      return this.finishNode(node, "ExportAllDeclaration");
+    }
+
+    const hasSpecifiers = this.maybeParseExportNamedSpecifiers(node);
+
+    if (
+      (hasDefault && parseAfterDefault && !hasStar && !hasSpecifiers) ||
+      (hasNamespace && parseAfterNamespace && !hasSpecifiers)
+    ) {
+      throw this.unexpected(null, tt.braceL);
+    }
+
+    let hasDeclaration;
+    if (isFromRequired || hasSpecifiers) {
+      hasDeclaration = false;
+      this.parseExportFrom(node, isFromRequired);
+    } else {
+      hasDeclaration = this.maybeParseExportDeclaration(node);
+    }
+
+    if (isFromRequired || hasSpecifiers || hasDeclaration) {
+      this.checkExport(node, true);
+      return this.finishNode(node, "ExportNamedDeclaration");
+    }
+
+    if (this.eat(tt._default)) {
       // export default ...
       node.declaration = this.parseExportDefaultExpression();
       this.checkExport(node, true, true);
+
       return this.finishNode(node, "ExportDefaultDeclaration");
-    } else if (this.shouldParseExportDeclaration()) {
+    }
+
+    throw this.unexpected(null, tt.braceL);
+  }
+
+  // eslint-disable-next-line no-unused-vars
+  eatExportStar(node: N.Node): boolean {
+    return this.eat(tt.star);
+  }
+
+  maybeParseExportDefaultSpecifier(node: N.Node): boolean {
+    if (this.isExportDefaultSpecifier()) {
+      // export defaultObj ...
+      this.expectPlugin("exportDefaultFrom");
+      const specifier = this.startNode();
+      specifier.exported = this.parseIdentifier(true);
+      node.specifiers = [this.finishNode(specifier, "ExportDefaultSpecifier")];
+      return true;
+    }
+    return false;
+  }
+
+  maybeParseExportNamespaceSpecifier(node: N.Node): boolean {
+    if (this.isContextual("as")) {
+      if (!node.specifiers) node.specifiers = [];
+      this.expectPlugin("exportNamespaceFrom");
+
+      const specifier = this.startNodeAt(
+        this.state.lastTokStart,
+        this.state.lastTokStartLoc,
+      );
+
+      this.next();
+
+      specifier.exported = this.parseIdentifier(true);
+      node.specifiers.push(
+        this.finishNode(specifier, "ExportNamespaceSpecifier"),
+      );
+      return true;
+    }
+    return false;
+  }
+
+  maybeParseExportNamedSpecifiers(node: N.Node): boolean {
+    if (this.match(tt.braceL)) {
+      if (!node.specifiers) node.specifiers = [];
+      node.specifiers.push(...this.parseExportSpecifiers());
+
+      node.source = null;
+      node.declaration = null;
+
+      return true;
+    }
+    return false;
+  }
+
+  maybeParseExportDeclaration(node: N.Node): boolean {
+    if (this.shouldParseExportDeclaration()) {
       if (this.isContextual("async")) {
         const next = this.lookahead();
 
@@ -1511,14 +1585,10 @@ export default class StatementParser extends ExpressionParser {
       node.specifiers = [];
       node.source = null;
       node.declaration = this.parseExportDeclaration(node);
-    } else {
-      // export { x, y as z } [from '...']
-      node.declaration = null;
-      node.specifiers = this.parseExportSpecifiers();
-      this.parseExportFrom(node);
+
+      return true;
     }
-    this.checkExport(node, true);
-    return this.finishNode(node, "ExportNamedDeclaration");
+    return false;
   }
 
   isAsyncFunction() {
@@ -1605,17 +1675,9 @@ export default class StatementParser extends ExpressionParser {
     );
   }
 
-  parseExportSpecifiersMaybe(node: N.ExportNamedDeclaration): void {
-    if (this.eat(tt.comma)) {
-      node.specifiers = node.specifiers.concat(this.parseExportSpecifiers());
-    }
-  }
-
   parseExportFrom(node: N.ExportNamedDeclaration, expect?: boolean): void {
     if (this.eatContextual("from")) {
-      node.source = this.match(tt.string)
-        ? this.parseExprAtom()
-        : this.unexpected();
+      node.source = this.parseImportSource();
       this.checkExport(node);
     } else {
       if (expect) {
@@ -1628,39 +1690,6 @@ export default class StatementParser extends ExpressionParser {
     this.semicolon();
   }
 
-  shouldParseExportStar(): boolean {
-    return this.match(tt.star);
-  }
-
-  parseExportStar(node: N.ExportNamedDeclaration): void {
-    this.expect(tt.star);
-
-    if (this.isContextual("as")) {
-      this.parseExportNamespace(node);
-    } else {
-      this.parseExportFrom(node, true);
-      this.finishNode(node, "ExportAllDeclaration");
-    }
-  }
-
-  parseExportNamespace(node: N.ExportNamedDeclaration): void {
-    this.expectPlugin("exportNamespaceFrom");
-
-    const specifier = this.startNodeAt(
-      this.state.lastTokStart,
-      this.state.lastTokStartLoc,
-    );
-
-    this.next();
-
-    specifier.exported = this.parseIdentifier(true);
-
-    node.specifiers = [this.finishNode(specifier, "ExportNamespaceSpecifier")];
-
-    this.parseExportSpecifiersMaybe(node);
-    this.parseExportFrom(node, true);
-  }
-
   shouldParseExportDeclaration(): boolean {
     if (this.match(tt.at)) {
       this.expectOnePlugin(["decorators", "decorators-legacy"]);
@@ -1760,27 +1789,24 @@ export default class StatementParser extends ExpressionParser {
   }
 
   checkDuplicateExports(
-    node: N.Identifier | N.ExportNamedDeclaration | N.ExportSpecifier,
+    node:
+      | N.Identifier
+      | N.ExportNamedDeclaration
+      | N.ExportSpecifier
+      | N.ExportDefaultSpecifier,
     name: string,
   ): void {
     if (this.state.exportedIdentifiers.indexOf(name) > -1) {
-      this.raiseDuplicateExportError(node, name);
+      throw this.raise(
+        node.start,
+        name === "default"
+          ? "Only one default export allowed per module."
+          : `\`${name}\` has already been exported. Exported identifiers must be unique.`,
+      );
     }
     this.state.exportedIdentifiers.push(name);
   }
 
-  raiseDuplicateExportError(
-    node: N.Identifier | N.ExportNamedDeclaration | N.ExportSpecifier,
-    name: string,
-  ): empty {
-    throw this.raise(
-      node.start,
-      name === "default"
-        ? "Only one default export allowed per module."
-        : `\`${name}\` has already been exported. Exported identifiers must be unique.`,
-    );
-  }
-
   // Parses a comma-separated list of module exports.
 
   parseExportSpecifiers(): Array<N.ExportSpecifier> {
@@ -1820,23 +1846,26 @@ export default class StatementParser extends ExpressionParser {
 
   // Parses import declaration.
 
-  parseImport(node: N.Node): N.ImportDeclaration | N.TsImportEqualsDeclaration {
+  parseImport(node: N.Node): N.AnyImport {
     // import '...'
-    if (this.match(tt.string)) {
-      node.specifiers = [];
-      node.source = this.parseExprAtom();
-    } else {
-      node.specifiers = [];
-      this.parseImportSpecifiers(node);
+    node.specifiers = [];
+    if (!this.match(tt.string)) {
+      const hasDefault = this.maybeParseDefaultImportSpecifier(node);
+      const parseNext = !hasDefault || this.eat(tt.comma);
+      const hasStar = parseNext && this.maybeParseStarImportSpecifier(node);
+      if (parseNext && !hasStar) this.parseNamedImportSpecifiers(node);
       this.expectContextual("from");
-      node.source = this.match(tt.string)
-        ? this.parseExprAtom()
-        : this.unexpected();
     }
+    node.source = this.parseImportSource();
     this.semicolon();
     return this.finishNode(node, "ImportDeclaration");
   }
 
+  parseImportSource(): N.StringLiteral {
+    if (!this.match(tt.string)) this.unexpected();
+    return this.parseExprAtom();
+  }
+
   // eslint-disable-next-line no-unused-vars
   shouldParseDefaultImport(node: N.ImportDeclaration): boolean {
     return this.match(tt.name);
@@ -1853,9 +1882,7 @@ export default class StatementParser extends ExpressionParser {
     node.specifiers.push(this.finishNode(specifier, type));
   }
 
-  // Parses a comma-separated list of module imports.
-  parseImportSpecifiers(node: N.ImportDeclaration): void {
-    let first = true;
+  maybeParseDefaultImportSpecifier(node: N.ImportDeclaration): boolean {
     if (this.shouldParseDefaultImport(node)) {
       // import defaultObj, { x, y as z } from '...'
       this.parseImportSpecifierLocal(
@@ -1864,10 +1891,12 @@ export default class StatementParser extends ExpressionParser {
         "ImportDefaultSpecifier",
         "default import specifier",
       );
-
-      if (!this.eat(tt.comma)) return;
+      return true;
     }
+    return false;
+  }
 
+  maybeParseStarImportSpecifier(node: N.ImportDeclaration): boolean {
     if (this.match(tt.star)) {
       const specifier = this.startNode();
       this.next();
@@ -1879,10 +1908,13 @@ export default class StatementParser extends ExpressionParser {
         "ImportNamespaceSpecifier",
         "import namespace specifier",
       );
-
-      return;
+      return true;
     }
+    return false;
+  }
 
+  parseNamedImportSpecifiers(node: N.ImportDeclaration) {
+    let first = true;
     this.expect(tt.braceL);
     while (!this.eat(tt.braceR)) {
       if (first) {

packages/babel-parser/src/plugins/flow.js

@@ -1847,17 +1847,15 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       super.assertModuleNodeAllowed(node);
     }
 
-    parseExport(
-      node: N.ExportNamedDeclaration | N.ExportAllDeclaration,
-    ): N.ExportNamedDeclaration | N.ExportAllDeclaration {
-      node = super.parseExport(node);
+    parseExport(node: N.Node): N.AnyExport {
+      const decl = super.parseExport(node);
       if (
-        node.type === "ExportNamedDeclaration" ||
-        node.type === "ExportAllDeclaration"
+        decl.type === "ExportNamedDeclaration" ||
+        decl.type === "ExportAllDeclaration"
       ) {
-        node.exportKind = node.exportKind || "value";
+        decl.exportKind = decl.exportKind || "value";
       }
-      return node;
+      return decl;
     }
 
     parseExportDeclaration(node: N.ExportNamedDeclaration): ?N.Declaration {
@@ -1893,27 +1891,26 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       }
     }
 
-    shouldParseExportStar(): boolean {
-      return (
-        super.shouldParseExportStar() ||
-        (this.isContextual("type") && this.lookahead().type === tt.star)
-      );
-    }
+    eatExportStar(node: N.Node): boolean {
+      if (super.eatExportStar(...arguments)) return true;
 
-    parseExportStar(node: N.ExportNamedDeclaration): void {
-      if (this.eatContextual("type")) {
+      if (this.isContextual("type") && this.lookahead().type === tt.star) {
         node.exportKind = "type";
+        this.next();
+        this.next();
+        return true;
       }
 
-      return super.parseExportStar(node);
+      return false;
     }
 
-    parseExportNamespace(node: N.ExportNamedDeclaration) {
-      if (node.exportKind === "type") {
-        this.unexpected();
+    maybeParseExportNamespaceSpecifier(node: N.Node): boolean {
+      const pos = this.state.start;
+      const hasNamespace = super.maybeParseExportNamespaceSpecifier(node);
+      if (hasNamespace && node.exportKind === "type") {
+        this.unexpected(pos);
       }
-
-      return super.parseExportNamespace(node);
+      return hasNamespace;
     }
 
     parseClassId(node: N.Class, isStatement: boolean, optionalId: ?boolean) {
@@ -2225,7 +2222,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
     }
 
     // parse typeof and type imports
-    parseImportSpecifiers(node: N.ImportDeclaration): void {
+    maybeParseDefaultImportSpecifier(node: N.ImportDeclaration): boolean {
       node.importKind = "value";
 
       let kind = null;
@@ -2252,7 +2249,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         }
       }
 
-      super.parseImportSpecifiers(node);
+      return super.maybeParseDefaultImportSpecifier(node);
     }
 
     // parse import-type/typeof shorthand

packages/babel-parser/src/plugins/typescript.js

@@ -1615,16 +1615,14 @@ export default (superClass: Class<Parser>): Class<Parser> =>
     */
     checkDuplicateExports() {}
 
-    parseImport(
-      node: N.Node,
-    ): N.ImportDeclaration | N.TsImportEqualsDeclaration {
+    parseImport(node: N.Node): N.AnyImport {
       if (this.match(tt.name) && this.lookahead().type === tt.eq) {
         return this.tsParseImportEqualsDeclaration(node);
       }
       return super.parseImport(node);
     }
 
-    parseExport(node: N.Node): N.Node {
+    parseExport(node: N.Node): N.AnyExport {
       if (this.match(tt._import)) {
         // `export import A = B;`
         this.expect(tt._import);

packages/babel-parser/src/types.js

@@ -783,7 +783,9 @@ export type AnyExport =
   | ExportNamedDeclaration
   | ExportDefaultDeclaration
   | ExportAllDeclaration
-  | TsExportAssignment;
+  | TsExportAssignment
+  | TsImportEqualsDeclaration
+  | TsNamespaceExportDeclaration;
 
 export type ModuleSpecifier = NodeBase & {
   local: Identifier,
@@ -820,7 +822,7 @@ export type ImportNamespaceSpecifier = ModuleSpecifier & {
 export type ExportNamedDeclaration = NodeBase & {
   type: "ExportNamedDeclaration",
   declaration: ?Declaration,
-  specifiers: $ReadOnlyArray<ExportSpecifier>,
+  specifiers: $ReadOnlyArray<ExportSpecifier | ExportDefaultSpecifier>,
   source: ?Literal,
 
   exportKind?: "type" | "value", // TODO: Not in spec
@@ -831,6 +833,11 @@ export type ExportSpecifier = NodeBase & {
   exported: Identifier,
 };
 
+export type ExportDefaultSpecifier = NodeBase & {
+  type: "ExportDefaultSpecifier",
+  exported: Identifier,
+};
+
 export type ExportDefaultDeclaration = NodeBase & {
   type: "ExportDefaultDeclaration",
   declaration:

packages/babel-parser/test/fixtures/experimental/export-extensions/default-and-named/output.json

@@ -145,7 +145,8 @@
             "raw": "\"bar\""
           },
           "value": "bar"
-        }
+        },
+        "declaration": null
       }
     ],
     "directives": []

packages/babel-parser/test/fixtures/experimental/export-extensions/ns-and-named/output.json

@@ -145,7 +145,8 @@
             "raw": "\"bar\""
           },
           "value": "bar"
-        }
+        },
+        "declaration": null
       }
     ],
     "directives": []