feat!: use Node.js' source-map cache, to support tools like ts-node (#152)

BREAKING CHANGE: Node.js' source-map and lineLength cache is now used to remap coverage output (this allows tools like ts-node to be supported, which transpile at runtime).

Author: Benjamin E. Coe

.travis.yml

@@ -4,5 +4,5 @@ os:
   - osx
   - windows
 node_js:
-  - "12"
+  - "13"
 after_success: npm run coverage

lib/report.js

@@ -32,6 +32,7 @@ class Report {
       include: include
     })
     this.omitRelative = omitRelative
+    this.sourceMapCache = {}
     this.wrapperLength = wrapperLength
   }
 
@@ -63,8 +64,9 @@ class Report {
 
     for (const v8ScriptCov of v8ProcessCov.result) {
       try {
+        const sources = this._getSourceMap(v8ScriptCov)
         const path = resolve(this.resolve, v8ScriptCov.url)
-        const converter = v8toIstanbul(path, this.wrapperLength)
+        const converter = v8toIstanbul(path, this.wrapperLength, sources)
         await converter.load()
 
         if (resultCountPerPath.has(path)) {
@@ -98,6 +100,34 @@ class Report {
     return this._allCoverageFiles
   }
 
+  /**
+   * Returns source-map and fake source file, if cached during Node.js'
+   * execution. This is used to support tools like ts-node, which transpile
+   * using runtime hooks.
+   *
+   * Note: requires Node.js 13+
+   *
+   * @return {Object} sourceMap and fake source file (created from line #s).
+   * @private
+   */
+  _getSourceMap (v8ScriptCov) {
+    const sources = {}
+    if (this.sourceMapCache[`file://${v8ScriptCov.url}`]) {
+      const sourceMapAndLineLengths = this.sourceMapCache[`file://${v8ScriptCov.url}`]
+      sources.sourceMap = {
+        sourcemap: sourceMapAndLineLengths.data
+      }
+      if (sourceMapAndLineLengths.lineLengths) {
+        let source = ''
+        sourceMapAndLineLengths.lineLengths.forEach(length => {
+          source += `${''.padEnd(length, '.')}\n`
+        })
+        sources.source = source
+      }
+    }
+    return sources
+  }
+
   /**
    * Returns the merged V8 process coverage.
    *
@@ -111,6 +141,9 @@ class Report {
     const v8ProcessCovs = []
     for (const v8ProcessCov of this._loadReports()) {
       if (this._isCoverageObject(v8ProcessCov)) {
+        if (v8ProcessCov['source-map-cache']) {
+          Object.assign(this.sourceMapCache, v8ProcessCov['source-map-cache'])
+        }
         v8ProcessCovs.push(this._normalizeProcessCov(v8ProcessCov))
       }
     }

package-lock.json

@@ -41,7 +41,7 @@
     "istanbul-reports": "^2.2.6",
     "rimraf": "^3.0.0",
     "test-exclude": "^5.2.3",
-    "v8-to-istanbul": "^3.2.3",
+    "v8-to-istanbul": "^3.2.6",
     "yargs": "^14.0.0",
     "yargs-parser": "^14.0.0"
   },
@@ -51,7 +51,9 @@
     "coveralls": "^3.0.6",
     "mocha": "^6.2.0",
     "standard": "^14.1.0",
-    "standard-version": "^7.0.0"
+    "standard-version": "^7.0.0",
+    "ts-node": "^8.4.1",
+    "typescript": "^3.6.4"
   },
   "engines": {
     "node": ">=10.12.0"

package.json

@@ -0,0 +1,34 @@
+export interface FooOptions {
+  x: number;
+}
+
+class Foo {
+  x: number;
+  constructor (options: FooOptions) {
+    this.x = options.x ? options.x : 99
+    if (this.x) {
+      console.info('covered')
+    } else {
+      console.info('uncovered')
+    }
+    this.methodC()
+  }
+  methodA (): number {
+    console.info('covered')
+    return 33
+  }
+  /* c8 ignore next 3 */
+  methodB () {
+    console.info('uncovered')
+  }
+  private methodC () {
+    console.info('covered')
+  }
+  methodD () {
+    console.info('uncovered')
+  }
+}
+
+const a = new Foo({x: 0})
+const b = new Foo({x: 33})
+a.methodA()

test/fixtures/source-maps/branches/branches.uglify.js.map

@@ -311,4 +311,20 @@ describe('c8', () => {
       })
     })
   })
+
+  describe('ts-node', () => {
+    beforeEach(cb => rimraf('tmp/source-map', cb))
+
+    it('reads source-map from cache, and applies to coverage', () => {
+      const { output } = spawnSync(nodePath, [
+        c8Path,
+        '--exclude="test/*.js"',
+        '--temp-directory=tmp/source-map',
+        '--clean=true',
+        './node_modules/.bin/ts-node',
+        require.resolve('./fixtures/ts-node-basic.ts')
+      ])
+      output.toString('utf8').should.matchSnapshot()
+    })
+  })
 })

test/fixtures/source-maps/classes/classes.uglify.js.map

@@ -219,3 +219,18 @@ All files  |    83.33 |    85.71 |       60 |    83.33 |                   |
 -----------|----------|----------|----------|----------|-------------------|
 ,"
 `;
+
+exports[`c8 ts-node reads source-map from cache, and applies to coverage 1`] = `
+",covered
+covered
+covered
+covered
+covered
+------------------|----------|----------|----------|----------|-------------------|
+File              |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
+------------------|----------|----------|----------|----------|-------------------|
+All files         |    88.24 |     87.5 |       80 |    88.24 |                   |
+ ts-node-basic.ts |    88.24 |     87.5 |       80 |    88.24 |       12,13,28,29 |
+------------------|----------|----------|----------|----------|-------------------|
+,"
+`;