fix(perf): optimize hit counting and source map performance

Fixes #159

.editorconfig

@@ -0,0 +1,4 @@
+[*.{.js,.json}]
+end_of_line = lf
+indent_size = 2
+indent_style = space

.gitattributes

@@ -1,3 +1,6 @@
 test/fixtures/scripts/needs-compile.js eol=crlf
 test/fixtures/scripts/needs-compile.compiled.js eol=crlf
-test/fixtures/scripts/needs-compile.compiled.js.map eol=crlf
+test/fixtures/scripts/needs-compile.compiled.js.map eol=crlf
+test/fixtures/scripts/branches.covered.js eol=lf
+test/fixtures/scripts/branches.js eol=lf
+test/fixtures/scripts/functions.js eol=lf

.gitignore

@@ -4,3 +4,5 @@ coverage
 node_modules
 .idea
 .vscode
+*.iml
+yarn.lock

lib/range.js

@@ -0,0 +1,33 @@
+/**
+ * ...something resembling a binary search, to find the lowest line within the range.
+ * And then you could break as soon as the line is longer than the range...
+ */
+module.exports.sliceRange = (lines, startCol, endCol, inclusive = false) => {
+  let start = 0
+  let end = lines.length - 1
+
+  /**
+   * I consider this a temporary solution until I find an alternaive way to fix the "off by one issue"
+   */
+  const extStartCol = inclusive ? startCol - 1 : startCol
+
+  while (start < end) {
+    const mid = (start + end) >> 1
+    if (lines[mid].startCol <= startCol && lines[mid].endCol > extStartCol) {
+      start = mid
+      end = start
+    } else if (lines[mid].startCol > startCol) {
+      end = mid - 1
+    } else {
+      start = mid + 1
+    }
+  }
+  if (start === end) {
+    while (end < lines.length && extStartCol < lines[end].endCol && endCol >= lines[end].startCol) {
+      ++end
+    }
+    return lines.slice(start, end)
+  } else {
+    return []
+  }
+}

lib/source.js

@@ -1,4 +1,5 @@
 const CovLine = require('./line')
+const { sliceRange } = require('./range')
 const { GREATEST_LOWER_BOUND, LEAST_UPPER_BOUND } = require('source-map').SourceMapConsumer
 
 module.exports = class CovSource {
@@ -75,27 +76,24 @@ module.exports = class CovSource {
   // given a start column and end column in absolute offsets within
   // a source file (0 - EOF), returns the relative line column positions.
   offsetToOriginalRelative (sourceMap, startCol, endCol) {
-    const lines = this.lines.filter((line, i) => {
-      return startCol <= line.endCol && endCol >= line.startCol
-    })
+    const lines = sliceRange(this.lines, startCol, endCol, true)
     if (!lines.length) return {}
 
     const start = originalPositionTryBoth(
       sourceMap,
       lines[0].line,
       Math.max(0, startCol - lines[0].startCol)
     )
+    if (!(start && start.source)) {
+      return {}
+    }
+
     let end = originalEndPositionFor(
       sourceMap,
       lines[lines.length - 1].line,
       endCol - lines[lines.length - 1].startCol
     )
-
-    if (!(start && end)) {
-      return {}
-    }
-
-    if (!(start.source && end.source)) {
+    if (!(end && end.source)) {
       return {}
     }
 

lib/v8-to-istanbul.js

@@ -5,6 +5,7 @@ const { fileURLToPath } = require('url')
 const CovBranch = require('./branch')
 const CovFunction = require('./function')
 const CovSource = require('./source')
+const { sliceRange } = require('./range')
 const compatError = Error(`requires Node.js ${require('../package.json').engines.node}`)
 let readFile = () => { throw compatError }
 try {
@@ -112,22 +113,25 @@ module.exports = class V8ToIstanbul {
         if (this.excludePath(path)) {
           return
         }
-        const lines = covSource.lines.filter(line => {
-          // Upstream tooling can provide a block with the functionName
-          // (empty-report), this will result in a report that has all
-          // lines zeroed out.
-          if (block.functionName === '(empty-report)') {
+        let lines
+        if (block.functionName === '(empty-report)') {
+          // (empty-report), this will result in a report that has all lines zeroed out.
+          lines = covSource.lines.filter((line) => {
             line.count = 0
-            this.all = true
             return true
-          }
+          })
+          this.all = lines.length > 0
+        } else {
+          lines = sliceRange(covSource.lines, startCol, endCol)
+        }
+        if (!lines.length) {
+          return
+        }
 
-          return startCol < line.endCol && endCol >= line.startCol
-        })
         const startLineInstance = lines[0]
         const endLineInstance = lines[lines.length - 1]
 
-        if (block.isBlockCoverage && lines.length) {
+        if (block.isBlockCoverage) {
           this.branches[path] = this.branches[path] || []
           // record branches.
           this.branches[path].push(new CovBranch(
@@ -138,7 +142,7 @@ module.exports = class V8ToIstanbul {
             range.count
           ))
 
-          // if block-level granularity is enabled, we we still create a single
+          // if block-level granularity is enabled, we still create a single
           // CovFunction tracking object for each set of ranges.
           if (block.functionName && i === 0) {
             this.functions[path] = this.functions[path] || []
@@ -151,7 +155,7 @@ module.exports = class V8ToIstanbul {
               range.count
             ))
           }
-        } else if (block.functionName && lines.length) {
+        } else if (block.functionName) {
           this.functions[path] = this.functions[path] || []
           // record functions.
           this.functions[path].push(new CovFunction(

tap-snapshots/test/v8-to-istanbul.js.test.cjs

@@ -1877,38 +1877,9 @@ Object {
     "0": Array [
       1,
     ],
-    "1": Array [
-      1,
-    ],
   },
   "branchMap": Object {
     "0": Object {
-      "line": 2,
-      "loc": Object {
-        "end": Object {
-          "column": 7,
-          "line": 8,
-        },
-        "start": Object {
-          "column": -1,
-          "line": 2,
-        },
-      },
-      "locations": Array [
-        Object {
-          "end": Object {
-            "column": 7,
-            "line": 8,
-          },
-          "start": Object {
-            "column": -1,
-            "line": 2,
-          },
-        },
-      ],
-      "type": "branch",
-    },
-    "1": Object {
       "line": 2,
       "loc": Object {
         "end": Object {

test/range.js

@@ -0,0 +1,35 @@
+/* global describe, it */
+const { sliceRange } = require('../lib/range')
+
+require('tap').mochaGlobals()
+require('should')
+
+describe('range', () => {
+  describe('slice range', () => {
+    it('can deal with empty arrays', () => {
+      sliceRange([], 0, 1).should.eql([])
+    })
+    it('can find lines that match exactly', () => {
+      const THREE_LINES = [
+        { startCol: 0, endCol: 10 },
+        { startCol: 11, endCol: 20 },
+        { startCol: 21, endCol: 30 }
+      ]
+      sliceRange(THREE_LINES, 0, 10).should.eql([THREE_LINES[0]])
+      sliceRange(THREE_LINES, 11, 20).should.eql([THREE_LINES[1]])
+      sliceRange(THREE_LINES, 21, 30).should.eql([THREE_LINES[2]])
+    })
+    it('can cover a range that spans two lines', () => {
+      const SIX_LINES = [
+        { startCol: 0, endCol: 3 },
+        { startCol: 4, endCol: 10 },
+        { startCol: 11, endCol: 14 },
+        { startCol: 15, endCol: 20 },
+        { startCol: 21, endCol: 24 },
+        { startCol: 25, endCol: 30 }
+      ]
+      sliceRange(SIX_LINES, 5, 14).should.eql(SIX_LINES.slice(1, 3))
+      sliceRange(SIX_LINES, 15, 21).should.eql(SIX_LINES.slice(3, 5))
+    })
+  })
+})

test/source.js

@@ -1,6 +1,7 @@
 /* global describe, it */
 
 const CovSource = require('../lib/source')
+const { SourceMapConsumer } = require('source-map')
 
 require('tap').mochaGlobals()
 require('should')
@@ -38,6 +39,30 @@ describe('Source', () => {
       const source = new CovSource(sourceRaw, 0)
       source.offsetToOriginalRelative(undefined, Infinity, Infinity).should.deepEqual({})
     })
+
+    it('range crossing two sourcemaps', async () => {
+      const sourceRaw = `\
+(() => {
+  // hello.ts
+  function hello() {
+    console.log("hello world");
+  }
+
+  // greet.ts
+  hello();
+})();
+//# sourceMappingURL=greet.js.map\
+`
+      const source = new CovSource(sourceRaw, 0)
+      const sourceMap = await new SourceMapConsumer({
+        version: 3,
+        sources: ['../hello.ts', '../greet.ts'],
+        sourcesContent: ['export function hello() {\r\n  console.log("hello world")\r\n}', 'import {hello} from "./hello"\r\n\r\nhello()\r\n'],
+        mappings: ';;AAAO,mBAAiB;AACtB,YAAQ,IAAI;AAAA;;;ACCd;',
+        names: []
+      })
+      source.offsetToOriginalRelative(sourceMap, 25, 97).should.deepEqual({})
+    })
   })
 
   describe('ignore', () => {