1 files changed, 126 insertions, 0 deletions
diff --git a/tools/code-coverage/PerTestCoverageUtils.jsm b/tools/code-coverage/PerTestCoverageUtils.jsm
new file mode 100644
index 0000000000..f1945273c1
--- /dev/null
+++ b/tools/code-coverage/PerTestCoverageUtils.jsm
@@ -0,0 +1,126 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* exported PerTestCoverageUtils */
+
+"use strict";
+
+var EXPORTED_SYMBOLS = ["PerTestCoverageUtils"];
+
+// This is the directory where gcov is emitting the gcda files.
+const gcovPrefixPath = Services.env.get("GCOV_PREFIX");
+// This is the directory where codecoverage.py is expecting to see the gcda files.
+const gcovResultsPath = Services.env.get("GCOV_RESULTS_DIR");
+// This is the directory where the JS engine is emitting the lcov files.
+const jsvmPrefixPath = Services.env.get("JS_CODE_COVERAGE_OUTPUT_DIR");
+// This is the directory where codecoverage.py is expecting to see the lcov files.
+const jsvmResultsPath = Services.env.get("JSVM_RESULTS_DIR");
+
+const gcovPrefixDir = Cc["@mozilla.org/file/local;1"].createInstance(
+  Ci.nsIFile
+);
+if (gcovPrefixPath) {
+  gcovPrefixDir.initWithPath(gcovPrefixPath);
+}
+
+let gcovResultsDir = Cc["@mozilla.org/file/local;1"].createInstance(Ci.nsIFile);
+if (gcovResultsPath) {
+  gcovResultsDir.initWithPath(gcovResultsPath);
+}
+
+const jsvmPrefixDir = Cc["@mozilla.org/file/local;1"].createInstance(
+  Ci.nsIFile
+);
+if (jsvmPrefixPath) {
+  jsvmPrefixDir.initWithPath(jsvmPrefixPath);
+}
+
+let jsvmResultsDir = Cc["@mozilla.org/file/local;1"].createInstance(Ci.nsIFile);
+if (jsvmResultsPath) {
+  jsvmResultsDir.initWithPath(jsvmResultsPath);
+}
+
+function awaitPromise(promise) {
+  let ret;
+  let complete = false;
+  let error = null;
+  promise
+    .catch(e => (error = e))
+    .then(v => {
+      ret = v;
+      complete = true;
+    });
+  Services.tm.spinEventLoopUntil(
+    "PerTestCoverageUtils.jsm:awaitPromise",
+    () => complete
+  );
+  if (error) {
+    throw new Error(error);
+  }
+  return ret;
+}
+
+function removeDirectoryContents(dir) {
+  let entries = dir.directoryEntries;
+  while (entries.hasMoreElements()) {
+    entries.nextFile.remove(true);
+  }
+}
+
+function moveDirectoryContents(src, dst) {
+  let entries = src.directoryEntries;
+  while (entries.hasMoreElements()) {
+    entries.nextFile.moveTo(dst, null);
+  }
+}
+
+var PerTestCoverageUtils = class PerTestCoverageUtilsClass {
+  // Resets the counters to 0.
+  static async beforeTest() {
+    if (!PerTestCoverageUtils.enabled) {
+      return;
+    }
+
+    // Flush the counters.
+    let codeCoverageService = Cc[
+      "@mozilla.org/tools/code-coverage;1"
+    ].getService(Ci.nsICodeCoverage);
+    await codeCoverageService.flushCounters();
+
+    // Remove coverage files created by the flush, and those that might have been created between the end of a previous test and the beginning of the next one (e.g. some tests can create a new content process for every sub-test).
+    removeDirectoryContents(gcovPrefixDir);
+    removeDirectoryContents(jsvmPrefixDir);
+
+    // Move coverage files from the GCOV_RESULTS_DIR and JSVM_RESULTS_DIR directories, so we can accumulate the counters.
+    moveDirectoryContents(gcovResultsDir, gcovPrefixDir);
+    moveDirectoryContents(jsvmResultsDir, jsvmPrefixDir);
+  }
+
+  static beforeTestSync() {
+    awaitPromise(this.beforeTest());
+  }
+
+  // Dumps counters and moves the gcda files in the directory expected by codecoverage.py.
+  static async afterTest() {
+    if (!PerTestCoverageUtils.enabled) {
+      return;
+    }
+
+    // Flush the counters.
+    let codeCoverageService = Cc[
+      "@mozilla.org/tools/code-coverage;1"
+    ].getService(Ci.nsICodeCoverage);
+    await codeCoverageService.flushCounters();
+
+    // Move the coverage files in GCOV_RESULTS_DIR and JSVM_RESULTS_DIR, so that the execution from now to shutdown (or next test) is not counted.
+    moveDirectoryContents(gcovPrefixDir, gcovResultsDir);
+    moveDirectoryContents(jsvmPrefixDir, jsvmResultsDir);
+  }
+
+  static afterTestSync() {
+    awaitPromise(this.afterTest());
+  }
+};
+
+PerTestCoverageUtils.enabled = !!gcovResultsPath;