fix: v8 coverage ranges that fall on \n characters cause exceptions

.gitattributes

@@ -0,0 +1,3 @@
+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

.gitignore

@@ -2,3 +2,4 @@
 coverage
 .nyc_output
 node_modules
+.idea

lib/source.js

@@ -56,7 +56,7 @@ module.exports = class CovSource {
     const start = originalPositionTryBoth(
       sourceMap,
       lines[0].line,
-      startCol - lines[0].startCol
+      Math.max(0, startCol - lines[0].startCol)
     )
     let end = originalEndPositionFor(
       sourceMap,

test/fixtures/scripts/needs-compile.js

@@ -0,0 +1,32 @@
+// compile me with babel 7+:
+// > babel --plugins @babel/plugin-proposal-class-properties test/fixtures/scripts/needs-compile.js --out-file test/fixtures/scripts/needs-compile.compiled.js --source-maps
+// in addition, a .gitattribute clause forces this file and its compilation assets to crlf
+
+// class uses private class fields - must be compiled
+// hello is called
+class Foo {
+  a = 1
+  #b = 2
+  constructor () {
+    this.c = this.a + this.#b;
+  }
+  hello (i) {
+    console.info('hello:', this.c + i)
+  }
+}
+
+// class uses private class fields - must be compiled
+// hello is never called
+class Bar {
+  #test = 99
+  constructor () {
+  }
+  hello () {
+    console.info(`Hello ${this.#test}`)
+  }
+}
+
+const foo = new Foo();
+foo.hello(1)
+const bar = new Bar()
+

test/v8-to-istanbul.js

@@ -6,6 +6,7 @@ const V8ToIstanbul = require('../lib/v8-to-istanbul')
 const crypto = require('crypto')
 const os = require('os')
 const sourcemap = require('source-map')
+const assert = require('assert')
 
 require('tap').mochaGlobals()
 require('should')
@@ -88,6 +89,36 @@ ${'//'}${'#'} sourceMappingURL=data:application/json;base64,${base64Sourcemap}
       // that means it was bale to access the content via the provided sources object
       v8ToIstanbul.sourceTranspiled.should.not.be.undefined()
     })
+
+    it('should clamp line source column >= 0', async () => {
+      const v8ToIstanbul = new V8ToIstanbul(
+        `file://${require.resolve('./fixtures/scripts/needs-compile.compiled.js')}`,
+        0
+      )
+
+      // read the file and find the first end of line char
+      const fileBody = readFileSync(require.resolve('./fixtures/scripts/needs-compile.compiled.js')).toString()
+      const matchedNewLineChar = fileBody.match(/(?<=\r?\n)/u).index
+
+      // this isn't an assertion for the test so much as it is an assertion that the
+      // test fixture hasn't be reverted from \r\n to \n.
+      assert(fileBody.substring(matchedNewLineChar - 2, matchedNewLineChar) === '\r\n', 'The test fixture is misconfigured!')
+
+      await v8ToIstanbul.load()
+      // apply a fake range that starts with the matched new line
+      // (these ranges can occur on v8 running on windows) and verify
+      // coverage is applied correctly. CovLine will have a
+      // gap between the endCol of the previous line ending on \r and startCol of the
+      // next line. This would cause -1 to be sent for the source map lookup.
+      // This would cause source map translation to throw
+      v8ToIstanbul.applyCoverage([{
+        functionName: 'fake',
+        ranges: [{
+          startOffset: matchedNewLineChar - 1,
+          endOffset: matchedNewLineChar + 10
+        }]
+      }])
+    })
   })
   describe('source map format edge cases', () => {
     let consoleWarn