feat: exclude lines that are missing from source maps

Author: AriPerkkio

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

@@ -58,8 +58,8 @@ 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.sourceMap), path: this.sourceMap.sources[i] }))
+        this.sourceTranspiled = new CovSource(rawSource, this.wrapperLength, this.sourceMap)
       } 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 +82,8 @@ 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.sourceMap), path: this.path }]
+        this.sourceTranspiled = new CovSource(rawSource, this.wrapperLength, this.sourceMap)
       }
     } else {
       this.covSources = [{ source: new CovSource(rawSource, this.wrapperLength), path: this.path }]