Fix(estree): Reset export's start after decorator

eslint/babel-eslint-tests/test/integration/eslint/verify.js

@@ -2,6 +2,32 @@ import verifyAndAssertMessages from "../../helpers/verifyAndAssertMessages.js";
 import path from "path";
 import { fileURLToPath } from "url";
 
+function verifyDecoratorsLegacyAndAssertMessages(
+  code,
+  rules,
+  expectedMessages,
+  sourceType,
+) {
+  const overrideConfig = {
+    parserOptions: {
+      sourceType,
+      babelOptions: {
+        configFile: path.resolve(
+          path.dirname(fileURLToPath(import.meta.url)),
+          "../../../../babel-eslint-shared-fixtures/config/babel.config.decorators-legacy.js",
+        ),
+      },
+    },
+  };
+  return verifyAndAssertMessages(
+    code,
+    rules,
+    expectedMessages,
+    sourceType,
+    overrideConfig,
+  );
+}
+
 describe("verify", () => {
   it("arrow function support (issue #1)", () => {
     verifyAndAssertMessages("describe('stuff', () => {});");
@@ -1073,32 +1099,6 @@ describe("verify", () => {
   });
 
   describe("decorators #72 (legacy)", () => {
-    function verifyDecoratorsLegacyAndAssertMessages(
-      code,
-      rules,
-      expectedMessages,
-      sourceType,
-    ) {
-      const overrideConfig = {
-        parserOptions: {
-          sourceType,
-          babelOptions: {
-            configFile: path.resolve(
-              path.dirname(fileURLToPath(import.meta.url)),
-              "../../../../babel-eslint-shared-fixtures/config/babel.config.decorators-legacy.js",
-            ),
-          },
-        },
-      };
-      return verifyAndAssertMessages(
-        code,
-        rules,
-        expectedMessages,
-        sourceType,
-        overrideConfig,
-      );
-    }
-
     it("class declaration", () => {
       verifyDecoratorsLegacyAndAssertMessages(
         `
@@ -1247,6 +1247,16 @@ describe("verify", () => {
     });
   });
 
+  describe("decorators #15085 (legacy)", () => {
+    it("works with keyword-spacing rule", () => {
+      verifyDecoratorsLegacyAndAssertMessages(
+        "@dec export class C {}; @dec export default class {}",
+        { "keyword-spacing": 1 },
+        [],
+      );
+    });
+  });
+
   it("detects minimal no-unused-vars case #120", () => {
     verifyAndAssertMessages("var unused;", { "no-unused-vars": 1 }, [
       "1:5 'unused' is defined but never used. no-unused-vars",

packages/babel-parser/src/plugins/estree.ts

@@ -455,6 +455,7 @@ export default (superClass: typeof Parser) =>
       unfinished: Undone<N.AnyExport>,
       decorators: N.Decorator[] | null,
     ) {
+      const exportStartLoc = this.state.lastTokStartLoc;
       const node = super.parseExport(unfinished, decorators);
 
       switch (node.type) {
@@ -476,6 +477,27 @@ export default (superClass: typeof Parser) =>
             delete node.specifiers;
           }
 
+        // fallthrough
+        case "ExportDefaultDeclaration":
+          {
+            const { declaration } = node;
+            if (
+              declaration?.type === "ClassDeclaration" &&
+              declaration.decorators?.length > 0 &&
+              // decorator comes before export
+              declaration.start === node.start
+            ) {
+              this.resetStartLocation(
+                node,
+                // For compatibility with ESLint's keyword-spacing rule, which assumes that an
+                // export declaration must start with export.
+                // https://github.com/babel/babel/issues/15085
+                // Here we reset export declaration's start to be the start of the export token
+                exportStartLoc,
+              );
+            }
+          }
+
           break;
       }
 

packages/babel-parser/test/fixtures/estree/export/decorator-before-export/input.js

@@ -0,0 +1,2 @@
+@dec export class C {}
+@dec export default class {}

packages/babel-parser/test/fixtures/estree/export/decorator-before-export/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": ["estree", "decorators-legacy"]
+}

packages/babel-parser/test/fixtures/estree/export/decorator-before-export/output.json

@@ -0,0 +1,70 @@
+{
+  "type": "File",
+  "start":0,"end":51,"loc":{"start":{"line":1,"column":0},"end":{"line":2,"column":28}},
+  "program": {
+    "type": "Program",
+    "start":0,"end":51,"loc":{"start":{"line":1,"column":0},"end":{"line":2,"column":28}},
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ExportNamedDeclaration",
+        "start":5,"end":22,"loc":{"start":{"line":1,"column":5},"end":{"line":1,"column":22}},
+        "specifiers": [],
+        "source": null,
+        "declaration": {
+          "type": "ClassDeclaration",
+          "start":0,"end":22,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":22}},
+          "id": {
+            "type": "Identifier",
+            "start":18,"end":19,"loc":{"start":{"line":1,"column":18},"end":{"line":1,"column":19},"identifierName":"C"},
+            "name": "C"
+          },
+          "superClass": null,
+          "body": {
+            "type": "ClassBody",
+            "start":20,"end":22,"loc":{"start":{"line":1,"column":20},"end":{"line":1,"column":22}},
+            "body": []
+          },
+          "decorators": [
+            {
+              "type": "Decorator",
+              "start":0,"end":4,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":4}},
+              "expression": {
+                "type": "Identifier",
+                "start":1,"end":4,"loc":{"start":{"line":1,"column":1},"end":{"line":1,"column":4},"identifierName":"dec"},
+                "name": "dec"
+              }
+            }
+          ]
+        }
+      },
+      {
+        "type": "ExportDefaultDeclaration",
+        "start":28,"end":51,"loc":{"start":{"line":2,"column":5},"end":{"line":2,"column":28}},
+        "declaration": {
+          "type": "ClassDeclaration",
+          "start":23,"end":51,"loc":{"start":{"line":2,"column":0},"end":{"line":2,"column":28}},
+          "id": null,
+          "superClass": null,
+          "body": {
+            "type": "ClassBody",
+            "start":49,"end":51,"loc":{"start":{"line":2,"column":26},"end":{"line":2,"column":28}},
+            "body": []
+          },
+          "decorators": [
+            {
+              "type": "Decorator",
+              "start":23,"end":27,"loc":{"start":{"line":2,"column":0},"end":{"line":2,"column":4}},
+              "expression": {
+                "type": "Identifier",
+                "start":24,"end":27,"loc":{"start":{"line":2,"column":1},"end":{"line":2,"column":4},"identifierName":"dec"},
+                "name": "dec"
+              }
+            }
+          ]
+        }
+      }
+    ]
+  }
+}