feat: exclude lines that are missing from source maps

index.d.ts

@@ -20,6 +20,6 @@ declare class V8ToIstanbul {
   toIstanbul(): CoverageMapData
 }
 
-declare function v8ToIstanbul(scriptPath: string, wrapperLength?: number, sources?: Sources, excludePath?: (path: string) => boolean): V8ToIstanbul
+declare function v8ToIstanbul(scriptPath: string, wrapperLength?: number, sources?: Sources, excludePath?: (path: string) => boolean, excludeEmptyLines?: boolean): V8ToIstanbul
 
 export = v8ToIstanbul

index.js

@@ -1,5 +1,5 @@
 const V8ToIstanbul = require('./lib/v8-to-istanbul')
 
-module.exports = function (path, wrapperLength, sources, excludePath) {
-  return new V8ToIstanbul(path, wrapperLength, sources, excludePath)
+module.exports = function (path, wrapperLength, sources, excludePath, excludeEmptyLines) {
+  return new V8ToIstanbul(path, wrapperLength, sources, excludePath, excludeEmptyLines)
 }

lib/source.js

@@ -1,23 +1,31 @@
 const CovLine = require('./line')
 const { sliceRange } = require('./range')
-const { originalPositionFor, generatedPositionFor, GREATEST_LOWER_BOUND, LEAST_UPPER_BOUND } = require('@jridgewell/trace-mapping')
+const { originalPositionFor, generatedPositionFor, eachMapping, GREATEST_LOWER_BOUND, LEAST_UPPER_BOUND } = require('@jridgewell/trace-mapping')
 
 module.exports = class CovSource {
-  constructor (sourceRaw, wrapperLength) {
+  constructor (sourceRaw, wrapperLength, traceMap) {
     sourceRaw = sourceRaw ? sourceRaw.trimEnd() : ''
     this.lines = []
     this.eof = sourceRaw.length
     this.shebangLength = getShebangLength(sourceRaw)
     this.wrapperLength = wrapperLength - this.shebangLength
-    this._buildLines(sourceRaw)
+    this._buildLines(sourceRaw, traceMap)
   }
 
-  _buildLines (source) {
+  _buildLines (source, traceMap) {
     let position = 0
     let ignoreCount = 0
     let ignoreAll = false
+    const linesToCover = traceMap && this._parseLinesToCover(traceMap)
+
     for (const [i, lineStr] of source.split(/(?<=\r?\n)/u).entries()) {
-      const line = new CovLine(i + 1, position, lineStr)
+      const lineNumber = i + 1
+      const line = new CovLine(lineNumber, position, lineStr)
+
+      if (linesToCover && !linesToCover.has(lineNumber)) {
+        line.ignore = true
+      }
+
       if (ignoreCount > 0) {
         line.ignore = true
         ignoreCount--
@@ -125,6 +133,18 @@ module.exports = class CovSource {
     if (this.lines[line - 1] === undefined) return this.eof
     return Math.min(this.lines[line - 1].startCol + relCol, this.lines[line - 1].endCol)
   }
+
+  _parseLinesToCover (traceMap) {
+    const linesToCover = new Set()
+
+    eachMapping(traceMap, (mapping) => {
+      if (mapping.originalLine !== null) {
+        linesToCover.add(mapping.originalLine)
+      }
+    })
+
+    return linesToCover
+  }
 }
 
 // this implementation is pulled over from istanbul-lib-sourcemap:

lib/v8-to-istanbul.js

@@ -25,12 +25,13 @@ const isNode8 = /^v8\./.test(process.version)
 const cjsWrapperLength = isOlderNode10 ? require('module').wrapper[0].length : 0
 
 module.exports = class V8ToIstanbul {
-  constructor (scriptPath, wrapperLength, sources, excludePath) {
+  constructor (scriptPath, wrapperLength, sources, excludePath, excludeEmptyLines) {
     assert(typeof scriptPath === 'string', 'scriptPath must be a string')
     assert(!isNode8, 'This module does not support node 8 or lower, please upgrade to node 10')
     this.path = parsePath(scriptPath)
     this.wrapperLength = wrapperLength === undefined ? cjsWrapperLength : wrapperLength
     this.excludePath = excludePath || (() => false)
+    this.excludeEmptyLines = excludeEmptyLines === true
     this.sources = sources || {}
     this.generatedLines = []
     this.branches = {}
@@ -58,8 +59,8 @@ module.exports = class V8ToIstanbul {
         if (!this.sourceMap.sourcesContent) {
           this.sourceMap.sourcesContent = await this.sourcesContentFromSources()
         }
-        this.covSources = this.sourceMap.sourcesContent.map((rawSource, i) => ({ source: new CovSource(rawSource, this.wrapperLength), path: this.sourceMap.sources[i] }))
-        this.sourceTranspiled = new CovSource(rawSource, this.wrapperLength)
+        this.covSources = this.sourceMap.sourcesContent.map((rawSource, i) => ({ source: new CovSource(rawSource, this.wrapperLength, this.excludeEmptyLines ? this.sourceMap : null), path: this.sourceMap.sources[i] }))
+        this.sourceTranspiled = new CovSource(rawSource, this.wrapperLength, this.excludeEmptyLines ? this.sourceMap : null)
       } else {
         const candidatePath = this.rawSourceMap.sourcemap.sources.length >= 1 ? this.rawSourceMap.sourcemap.sources[0] : this.rawSourceMap.sourcemap.file
         this.path = this._resolveSource(this.rawSourceMap, candidatePath || this.path)
@@ -82,8 +83,8 @@ module.exports = class V8ToIstanbul {
           // We fallback to reading the original source from disk.
           originalRawSource = await readFile(this.path, 'utf8')
         }
-        this.covSources = [{ source: new CovSource(originalRawSource, this.wrapperLength), path: this.path }]
-        this.sourceTranspiled = new CovSource(rawSource, this.wrapperLength)
+        this.covSources = [{ source: new CovSource(originalRawSource, this.wrapperLength, this.excludeEmptyLines ? this.sourceMap : null), path: this.path }]
+        this.sourceTranspiled = new CovSource(rawSource, this.wrapperLength, this.excludeEmptyLines ? this.sourceMap : null)
       }
     } else {
       this.covSources = [{ source: new CovSource(rawSource, this.wrapperLength), path: this.path }]

test/source.js

@@ -2,6 +2,7 @@
 
 const CovSource = require('../lib/source')
 const { TraceMap } = require('@jridgewell/trace-mapping')
+const assert = require('assert')
 
 require('tap').mochaGlobals()
 require('should')
@@ -68,6 +69,101 @@ describe('Source', () => {
       })
       source.offsetToOriginalRelative(sourceMap, 25, 97).should.deepEqual({})
     })
+
+    it('ignores empty lines', () => {
+      const sourceRaw = `\
+function add(a: number, b: number) {
+  /**
+   * Multi
+   * line
+   * comment
+   */
+  if (a === 2 && b === 3) {
+    // This line should NOT be covered
+    return 5;
+  }
+
+  type TypescriptTypings = 1 | 2;
+
+  if (a === 1 && b === 1) {
+    // Comment
+    return 2;
+  }
+
+  interface MoreCompileTimeCode {
+    should: {
+      be: {
+        excluded: true;
+      };
+    };
+  }
+
+  return a + b;
+}
+
+add(2, 5);
+`
+      const sourceMap = new TraceMap({
+        "version": 3,
+        "file": "index.js",
+        "sourceRoot": "",
+        "sources": [
+          "../src/index.ts"
+        ],
+        "names": [],
+        "mappings": ";AAAA,SAAS,GAAG,CAAC,CAAS,EAAE,CAAS;IAM/B,IAAI,CAAC,KAAK,CAAC,IAAI,CAAC,KAAK,CAAC,EAAE,CAAC;QAEvB,OAAO,CAAC,CAAC;IACX,CAAC;IAID,IAAI,CAAC,KAAK,CAAC,IAAI,CAAC,KAAK,CAAC,EAAE,CAAC;QAEvB,OAAO,CAAC,CAAC;IACX,CAAC;IAUD,OAAO,CAAC,GAAG,CAAC,CAAC;AACf,CAAC;AAED,GAAG,CAAC,CAAC,EAAE,CAAC,CAAC,CAAC"
+      }
+      )
+
+      const source = new CovSource(sourceRaw, 0, sourceMap)
+      const lines = source.lines;
+
+      assert.equal(lines[0].ignore, false)
+
+      // Multiline comment
+      assert.equal(lines[1].ignore, true)
+      assert.equal(lines[2].ignore, true)
+      assert.equal(lines[3].ignore, true)
+      assert.equal(lines[4].ignore, true)
+      assert.equal(lines[5].ignore, true)
+
+      // If-block with inline comment
+      assert.equal(lines[6].ignore, false)
+      assert.equal(lines[7].ignore, true)
+      assert.equal(lines[8].ignore, false)
+      assert.equal(lines[9].ignore, false)
+      assert.equal(lines[10].ignore, true)
+
+      // Typescript Type
+      assert.equal(lines[11].ignore, true)
+
+      // If-block with inline comment
+      assert.equal(lines[12].ignore, true)
+      assert.equal(lines[13].ignore, false)
+      assert.equal(lines[14].ignore, true)
+      assert.equal(lines[15].ignore, false)
+      assert.equal(lines[16].ignore, false)
+      assert.equal(lines[17].ignore, true)
+
+      // Typescript interface
+      assert.equal(lines[18].ignore, true)
+      assert.equal(lines[19].ignore, true)
+      assert.equal(lines[20].ignore, true)
+      assert.equal(lines[21].ignore, true)
+      assert.equal(lines[22].ignore, true)
+      assert.equal(lines[23].ignore, true)
+      assert.equal(lines[24].ignore, true)
+      assert.equal(lines[25].ignore, true)
+
+      // Return statement + function closing
+      assert.equal(lines[26].ignore, false)
+      assert.equal(lines[27].ignore, false)
+
+      // Function call
+      assert.equal(lines[28].ignore, true)
+      assert.equal(lines[29].ignore, false)
+
+    })
   })
 
   for (const prefix of ['c8', 'v8']) {