Fix: duplicated autofix output for inverted fix ranges (fixes #8116) (#…

…8117)

The padded-blocks rule sometimes produces a fix range where the start index of the range is larger than the end index. Due to the changes in fcc38db, when source-code-fixer encountered such a range, it would output the text between the end index and the start index twice. This commit ensures that source-code-fixer behaves the same way as it previously did when it encounters an inverted fix range (it should act as if the start and end indices were equal). In the future, we should also update padded-blocks to avoid producing inverted fix ranges.

lib/rules/padded-blocks.js

@@ -188,6 +188,9 @@ module.exports = {
                         node,
                         loc: { line: openBrace.loc.start.line, column: openBrace.loc.start.column },
                         fix(fixer) {
+
+                            // FIXME: The start of this range is sometimes larger than the end.
+                            // https://github.com/eslint/eslint/issues/8116
                             return fixer.replaceTextRange([openBrace.end, nextToken.start - nextToken.loc.start.column], "\n");
                         },
                         message: NEVER_MESSAGE

lib/util/source-code-fixer.js

@@ -108,7 +108,13 @@ SourceCodeFixer.applyFixes = function(sourceCode, messages) {
             // Make output to this fix.
             output += text.slice(Math.max(0, lastPos), Math.max(0, start));
             output += fix.text;
-            lastPos = end;
+
+            /*
+             * If the start of the range is larger than the end for some reason, make sure
+             * the text between the end and the start doesn't get duplicated.
+             * https://github.com/eslint/eslint/issues/8116
+             */
+            lastPos = Math.max(start, end);
         }
         output += text.slice(Math.max(0, lastPos));
 

tests/lib/rules/padded-blocks.js

@@ -463,6 +463,12 @@ ruleTester.run("padded-blocks", rule, {
                     line: 9
                 }
             ]
+        },
+        {
+            code: "function foo() { // a\n\n  b;\n}",
+            output: "function foo() {\n // a\n\n  b;\n}",
+            options: ["never"],
+            errors: [NEVER_MESSAGE]
         }
     ]
 });

tests/lib/util/source-code-fixer.js

@@ -122,6 +122,13 @@ const INSERT_AT_END = {
         message: "nofix2",
         line: 1,
         column: 7
+    },
+    REVERSED_RANGE = {
+        message: "reversed range",
+        fix: {
+            range: [3, 0],
+            text: " "
+        }
     };
 
 //------------------------------------------------------------------------------
@@ -407,6 +414,12 @@ describe("SourceCodeFixer", () => {
                 assert.equal(result.messages.length, 0);
             });
 
+            it("should handle reversed ranges gracefully", () => {
+                const result = SourceCodeFixer.applyFixes(sourceCode, [REVERSED_RANGE]);
+
+                assert.equal(result.output, "\uFEFFvar  answer = 6 * 7;");
+            });
+
         });
 
         describe("Text Replacement", () => {