Add 'dryRun' option to Linter

src/index.ts

@@ -39,12 +39,14 @@ export interface LintResult {
     warningCount: number;
     failures: RuleFailure[];
     fixes?: RuleFailure[];
+    fixedSources: Record<string, string>;
     format: string | FormatterConstructor;
     output: string;
 }
 
 export interface ILinterOptions {
     fix: boolean;
+    dryRun?: boolean;
     formatter?: string | FormatterConstructor;
     formattersDirectory?: string;
     rulesDirectory?: string | string[];

src/linter.ts

@@ -52,6 +52,7 @@ class Linter {
 
     private failures: RuleFailure[] = [];
     private fixes: RuleFailure[] = [];
+    private fixedSources: Record<string, string> = {};
 
     /**
      * Creates a TypeScript program object from a tsconfig.json file path and optional project directory.
@@ -137,6 +138,7 @@ class Linter {
         return {
             errorCount,
             failures: this.failures,
+            fixedSources: this.fixedSources,
             fixes: this.fixes,
             format: formatterName,
             output,
@@ -163,6 +165,7 @@ class Linter {
                 const fixableFailures = updatedFailures.filter((f) => f.hasFix());
                 this.fixes = this.fixes.concat(fixableFailures);
                 source = this.applyFixes(sourceFileName, source, fixableFailures);
+                this.fixedSources[sourceFileName] = source;
                 sourceFile = this.getSourceFile(sourceFileName, source);
             }
         }
@@ -176,15 +179,17 @@ class Linter {
     protected applyFixes(sourceFilePath: string, source: string, fixableFailures: RuleFailure[]): string {
         const fixesByFile = createMultiMap(fixableFailures, (f) => [f.getFileName(), f.getFix()!]);
         fixesByFile.forEach((fileFixes, filePath) => {
-            let fileNewSource: string;
+            let fileNewSource: string | undefined;
             if (path.resolve(filePath) === path.resolve(sourceFilePath)) {
                 source = Replacement.applyFixes(source, fileFixes);
                 fileNewSource = source;
-            } else {
+            } else if (!this.options.dryRun) {
                 const oldSource = fs.readFileSync(filePath, "utf-8");
                 fileNewSource = Replacement.applyFixes(oldSource, fileFixes);
             }
-            fs.writeFileSync(filePath, fileNewSource);
+            if (!this.options.dryRun && typeof fileNewSource === "string") {
+                fs.writeFileSync(filePath, fileNewSource);
+            }
             this.updateProgram(filePath);
         });
 

src/runner.ts

@@ -40,6 +40,11 @@ export interface Options {
      */
     config?: string;
 
+    /**
+     * When running with fix: true, do not write files to disk.
+     */
+    dryRun?: boolean;
+
     /**
      * Exclude globs from path expansion.
      */
@@ -211,6 +216,7 @@ async function doLinting(
     const possibleConfigAbsolutePath = options.config !== undefined ? path.resolve(options.config) : null;
     const linter = new Linter(
         {
+            dryRun: !!options.dryRun,
             fix: !!options.fix,
             formatter: options.format,
             formattersDirectory: options.formattersDirectory,

test/linterTests.ts

@@ -64,4 +64,16 @@ describe("Linter", () => {
         assert.equal(fs.readFileSync(templateFile, "utf-8"), templateDeclarationFixed);
     });
 
+    it("dry run does not write files to disk", () => {
+        const linter = new TestLinter({ fix: true, dryRun: true });
+        const templateFile = createTempFile("ts");
+        fs.writeFileSync(templateFile, templateDeclaration);
+        const sourceFile = createSourceFile(templateFile, `${templateDeclaration}`, ScriptTarget.ES2015);
+        const replacement = new Replacement(6, 9, "");
+        const failure = new RuleFailure(sourceFile, 6, 15, "Declaration doesn't exist", "foo-bar", replacement);
+        const result = linter.applyFixesHelper(templateFile, templateDeclaration, [failure]);
+        assert.equal(fs.readFileSync(templateFile, "utf-8"), templateDeclaration);
+        assert.equal(result, templateDeclarationFixed);
+    });
+
 });