Report removed files in baseline comparisons

README.md

@@ -42,6 +42,11 @@ typegap --baseline coverage.json
 typegap --compare coverage.json
 ```
 
+Baseline comparisons report changed and new files, plus files that were present
+in the saved baseline but are absent from the current scan. Removed files retain
+their previous coverage in both text and JSON output, so deleting a low-coverage
+file cannot appear as an unexplained overall improvement.
+
 The global install points at the checkout, so rebuild after pulling changes.
 When the first npm release is available, `npm install --global typegap` will
 become the registry installation path; it is not supported today.

src/reporter.test.ts

@@ -73,6 +73,32 @@ describe('generateReport', () => {
     ]);
   });
 
+  it('reports a removed low-coverage file behind an overall improvement', () => {
+    const removedFile = makeResult().files[0];
+    removedFile.file = 'removed.ts';
+    removedFile.coverage = 0;
+    const keptFile = { ...makeResult().files[0], file: 'kept.ts', coverage: 100 };
+    const oldResult = makeResult({ files: [removedFile, keptFile], coverage: 50 });
+    saveBaseline(oldResult, BASELINE_FILE);
+
+    const newResult = makeResult({ files: [keptFile], coverage: 100 });
+    const json = JSON.parse(generateReport(newResult, {
+      format: 'json',
+      compareBaseline: BASELINE_FILE,
+    }).output);
+    const text = generateReport(newResult, { compareBaseline: BASELINE_FILE }).output;
+
+    expect(json.comparison.coverageDelta).toBe(50);
+    expect(json.comparison.files).toEqual([
+      {
+        file: 'removed.ts',
+        coverageBefore: 0,
+        status: 'removed',
+      },
+    ]);
+    expect(text).toMatch(/removed\.ts:.*removed.*\(0\.0%\)/);
+  });
+
   it('returns exit code 0 when above min coverage', () => {
     const result = makeResult();
     const { exitCode } = generateReport(result, { minCoverage: 70 });

src/reporter.ts

@@ -103,7 +103,11 @@ export function compareWithBaseline(result: ProjectResult, baseline: Baseline, c
     }
 
     if (file.status === 'new') {
-      lines.push(`  ${file.file}: ${pc.yellow('new')} (${file.coverageCurrent.toFixed(1)}%)`);
+      lines.push(`  ${file.file}: ${pc.yellow('new')} (${file.coverageCurrent!.toFixed(1)}%)`);
+    }
+
+    if (file.status === 'removed') {
+      lines.push(`  ${file.file}: ${pc.yellow('removed')} (${file.coverageBefore!.toFixed(1)}%)`);
     }
   }
 
@@ -276,6 +280,8 @@ export function getBaselineComparison(
       continue;
     }
 
+    baselineMap.delete(filePath);
+
     const coverageDelta = round(f.coverage - prev.coverage);
     if (coverageDelta !== 0) {
       files.push({
@@ -288,6 +294,14 @@ export function getBaselineComparison(
     }
   }
 
+  for (const [filePath, prev] of baselineMap) {
+    files.push({
+      file: filePath,
+      coverageBefore: prev.coverage,
+      status: 'removed',
+    });
+  }
+
   return {
     baselineTimestamp: baseline.timestamp,
     coverageBefore: baseline.coverage,

src/types.ts

@@ -92,8 +92,8 @@ export interface BaselineComparison {
   files: Array<{
     file: string;
     coverageBefore?: number;
-    coverageCurrent: number;
+    coverageCurrent?: number;
     coverageDelta?: number;
-    status: 'changed' | 'new';
+    status: 'changed' | 'new' | 'removed';
   }>;
 }