fix(builtin): fix coverage source file paths

internal/coverage/lcov_merger-js.js

@@ -12,6 +12,7 @@ Object.defineProperty(exports, "__esModule", { value: true });
 const crypto = require("crypto");
 const fs = require("fs");
 const path = require("path");
+const readline = require("readline");
 function _getArg(argv, key) {
     return argv.find(a => a.startsWith(key)).split('=')[1];
 }
@@ -62,7 +63,15 @@ function main() {
             reporter: ['lcovonly']
         })
             .run();
-        fs.copyFileSync(path.join(c8OutputDir, 'lcov.info'), outputFile);
+        const inputFile = path.join(c8OutputDir, 'lcov.info');
+        const input = readline.createInterface({
+            input: fs.createReadStream(inputFile),
+        });
+        const output = fs.createWriteStream(outputFile);
+        input.on('line', line => {
+            const patched = line.replace('SF:../../../', 'SF:');
+            output.write(patched + '\n');
+        });
     });
 }
 if (require.main === module) {

internal/coverage/lcov_merger.ts

@@ -18,6 +18,7 @@
 import * as crypto from 'crypto';
 import * as fs from 'fs';
 import * as path from 'path';
+import * as readline from 'readline';
 
 function _getArg(argv: string[], key: string): string {
   return argv.find(a => a.startsWith(key))!.split('=')[1];
@@ -103,8 +104,18 @@ async function main() {
       })
       .run();
   // moves the report into the files bazel expects
-  // lcovonly names this file lcov.info
-  fs.copyFileSync(path.join(c8OutputDir, 'lcov.info'), outputFile);
+  // and fixes the paths as we're moving it up 3 dirs
+  const inputFile = path.join(c8OutputDir, 'lcov.info');
+  // we want to do this 1 line at a time to avoid using too much memory
+  const input = readline.createInterface({
+    input: fs.createReadStream(inputFile),
+  });
+  const output = fs.createWriteStream(outputFile);
+
+  input.on('line', line => {
+    const patched = line.replace('SF:../../../', 'SF:')
+    output.write(patched + '\n');
+  });
 }
 
 if (require.main === module) {