Apply fixes depending on the source file used in the failures

[mgechev]

Introduction

I'm working on a tool called codelyzer. It exports a few tslint rules which are Angular specific. Internally the tool resolves the templates and styles of Angular components, parses them and performs analysis over them.

Later, based on this analysis the tool produces diagnostics which not always should be reported in the source file which was initially analyzed by tslint, i.e. tslint may initially perform analysis over app.component.ts but the diagnostics can be reported to app.component.html. This happens by providing app.component.html as source file to the template visitor which extends RuleWalker internally.

Actual behavior

Currently the produced replacements which should be applied to templates or styles are applied to the TypeScript file of the component which references them.

Expected behavior

The fixes should be applied to the files where the failure is reported, i.e. if the failure is reported for app.component.html and the value of failure.getFileName() === 'app.component.html' then the fix should be applied to app.component.html.

Fix

The fix will require change in linter.ts, something like:

...
  if (this.options.fix) {
    for (const rule of enabledRules) {
      const ruleFailures = this.applyRule(rule, sourceFile);
      source = fs.readFileSync(fileName, { encoding: "utf-8" });
      const fixsPerFile = this.getFixesPerFile(ruleFailures);
      if (Object.keys(fixsPerFile).length > 0) {
        this.fixes = this.fixes.concat(ruleFailures);
        Object.keys(fixsPerFile)
          .forEach(function (failureFileName) {
            const currentFixes = fixsPerFile[failureFileName];
            const content = fs.readFileSync(failureFileName, { encoding: "utf-8" });
            content = Fix.applyAll(content, currentFixes);
            fs.writeFileSync(failureFileName, content, { encoding: "utf-8" });
            if (fileName === failureFileName) {
              sourceFile = this.getSourceFile(failureFileName, source);
            }
          });
      }
      fileFailures = fileFailures.concat(ruleFailures);
    }
    hasLinterRun = true;
  }
...

private getFixesPerFile(ruleFailures: RuleFailure[]) {
  return ruleFailures
    .reduce((accum, c) => {
      const fn = c.getFileName();
      accum[fn] = accum[fn] || [];
      const fix = c.getFix();
      if (fix) {
        accum[fn].push(fix);
      }
      return accum;
    }, {})
}

Let me know what you think. Would love to open a PR.

The final goal is to provide automatic migration for the deprecations introduced by Angular 4.

The change will not introduce any breaking changes and will not change the current behavior.

[mgechev]

Here's the PR #2421.