fix: Remove no-extra-semi autofix before potential directives (#17297)

Author: fasttime

docs/src/rules/no-extra-semi.md

@@ -16,6 +16,8 @@ Typing mistakes and misunderstandings about where semicolons are required can le
 
 This rule disallows unnecessary semicolons.
 
+Problems reported by this rule can be fixed automatically, except when removing a semicolon would cause a following statement to become a directive such as `"use strict"`.
+
 Examples of **incorrect** code for this rule:
 
 ::: incorrect

lib/rules/no-extra-semi.js

@@ -38,6 +38,23 @@ module.exports = {
     create(context) {
         const sourceCode = context.sourceCode;
 
+        /**
+         * Checks if a node or token is fixable.
+         * A node is fixable if it can be removed without turning a subsequent statement into a directive after fixing other nodes.
+         * @param {Token} nodeOrToken The node or token to check.
+         * @returns {boolean} Whether or not the node is fixable.
+         */
+        function isFixable(nodeOrToken) {
+            const nextToken = sourceCode.getTokenAfter(nodeOrToken);
+
+            if (!nextToken || nextToken.type !== "String") {
+                return true;
+            }
+            const stringNode = sourceCode.getNodeByRangeIndex(nextToken.range[0]);
+
+            return !astUtils.isTopLevelExpressionStatement(stringNode.parent);
+        }
+
         /**
          * Reports an unnecessary semicolon error.
          * @param {Node|Token} nodeOrToken A node or a token to be reported.
@@ -47,17 +64,18 @@ module.exports = {
             context.report({
                 node: nodeOrToken,
                 messageId: "unexpected",
-                fix(fixer) {
-
-                    /*
-                     * Expand the replacement range to include the surrounding
-                     * tokens to avoid conflicting with semi.
-                     * https://github.com/eslint/eslint/issues/7928
-                     */
-                    return new FixTracker(fixer, context.sourceCode)
-                        .retainSurroundingTokens(nodeOrToken)
-                        .remove(nodeOrToken);
-                }
+                fix: isFixable(nodeOrToken)
+                    ? fixer =>
+
+                        /*
+                         * Expand the replacement range to include the surrounding
+                         * tokens to avoid conflicting with semi.
+                         * https://github.com/eslint/eslint/issues/7928
+                         */
+                        new FixTracker(fixer, context.sourceCode)
+                            .retainSurroundingTokens(nodeOrToken)
+                            .remove(nodeOrToken)
+                    : null
             });
         }
 

tests/lib/rules/no-extra-semi.js

@@ -190,6 +190,43 @@ ruleTester.run("no-extra-semi", rule, {
             output: "class A { static { a; } foo(){} }",
             parserOptions: { ecmaVersion: 2022 },
             errors: [{ messageId: "unexpected", type: "Punctuator", column: 24 }]
+        },
+
+        // https://github.com/eslint/eslint/issues/16988
+        {
+            code: "; 'use strict'",
+            output: null,
+            errors: [{ messageId: "unexpected", type: "EmptyStatement" }]
+        },
+        {
+            code: "; ; 'use strict'",
+            output: " ; 'use strict'",
+            errors: [{ messageId: "unexpected", type: "EmptyStatement" }, { messageId: "unexpected", type: "EmptyStatement" }]
+        },
+        {
+            code: "debugger;\n;\n'use strict'",
+            output: null,
+            errors: [{ messageId: "unexpected", type: "EmptyStatement", line: 2 }]
+        },
+        {
+            code: "function foo() { ; 'bar'; }",
+            output: null,
+            errors: [{ messageId: "unexpected", type: "EmptyStatement" }]
+        },
+        {
+            code: "{ ; 'foo'; }",
+            output: "{  'foo'; }",
+            errors: [{ messageId: "unexpected", type: "EmptyStatement" }]
+        },
+        {
+            code: "; ('use strict');",
+            output: " ('use strict');",
+            errors: [{ messageId: "unexpected", type: "EmptyStatement" }]
+        },
+        {
+            code: "; 1;",
+            output: " 1;",
+            errors: [{ messageId: "unexpected", type: "EmptyStatement" }]
         }
     ]
 });