From 3f0ca71b7022a2c352cfc179ebd61ded3c48f465 Mon Sep 17 00:00:00 2001
From: Weimin Yu <weiminyu@google.com>
Date: Wed, 7 Aug 2019 11:21:04 -0400
Subject: [PATCH] Generate code coverage report (#216)

* Generate code coverage report

Enable jacoco, the official Gradle code coverage plugin.

The 'build' task will write a code coverage report to
build/reports/jacoco for each subproject that has tests.
We should consider publish periodical reports to a well known
location.

This change also defines a minimum coverage verification task.
The task is for experiment only, and is not added to the build
process yet.
---
 build.gradle                                  |  2 +
 .../dependency-license/allowed_licenses.json  |  3 ++
 java_common.gradle                            | 46 +++++++++++++++++++
 3 files changed, 51 insertions(+)

diff --git a/build.gradle b/build.gradle
index 2e09d5d59..beafc10c3 100644
--- a/build.gradle
+++ b/build.gradle
@@ -44,6 +44,8 @@ plugins {
 
   id 'idea'
   id 'com.diffplug.gradle.spotless' version '3.18.0'
+
+  id 'jacoco'
 }
 
 wrapper {
diff --git a/config/dependency-license/allowed_licenses.json b/config/dependency-license/allowed_licenses.json
index aca7c1a6d..06f87a4d9 100644
--- a/config/dependency-license/allowed_licenses.json
+++ b/config/dependency-license/allowed_licenses.json
@@ -108,6 +108,9 @@
     {
       "moduleLicense": "Eclipse Public License 1.0"
     },
+    {
+      "moduleLicense": "Eclipse Public License v1.0"
+    },
     {
       "moduleLicense": "Google App Engine Terms of Service"
     },
diff --git a/java_common.gradle b/java_common.gradle
index 0decea3a9..a0ac49265 100644
--- a/java_common.gradle
+++ b/java_common.gradle
@@ -17,11 +17,17 @@ apply plugin: 'nebula.lint'
 apply plugin: 'net.ltgt.apt'
 apply plugin: 'net.ltgt.errorprone'
 apply plugin: 'checkstyle'
+apply plugin: 'jacoco'
 
 // Checkstyle should run as part of the testing task
 tasks.test.dependsOn tasks.checkstyleMain
 tasks.test.dependsOn tasks.checkstyleTest
 
+// Generate per-subproject reports in build/reports/jacoco directory.
+// TODO(weiminyu): publish periodical reports to well known location.
+// TODO(weiminyu): investigate incremental coverage change calculation and alert.
+tasks.test.finalizedBy jacocoTestReport
+
 dependencies {
     // compatibility with Java 8
     errorproneJavac("com.google.errorprone:javac:9+181-r4173-1")
@@ -87,3 +93,43 @@ spotless {
     endWithNewline()
   }
 }
+
+// Initialize for coverage minimum determination for each sub project.
+task initCoverageMinimums {
+  // Use current coverage ratio of each subproject as placeholder value.
+  // Long-term plan is to calculate incremental coverage on the fly.
+  rootProject.ext.coverageMinimums = [
+     'core'    : 0.6,
+     'proxy'   : 0.52,
+     'util'    : 0.57
+  ].asImmutable()
+
+  rootProject.ext.getMinCoverage = { key ->
+    if (rootProject.ext.coverageMinimums.containsKey(key)) {
+      return rootProject.ext.coverageMinimums.get(key)
+    }
+    return 0.0
+  }
+}
+
+// Alerts for coverage violation. Note that,
+// - This task is FYI only and needs to be invoked explicitly.
+// - This task does not address incremental coverage.
+jacocoTestCoverageVerification {
+
+  dependsOn initCoverageMinimums
+
+  violationRules {
+    rule {
+      // Each limit consists of the following properties:
+      // - An 'element' type: BUNDLE (default), PACKAGE, CLASS, SOURCEFILE, or METHOD.
+      // - A 'counter' type: INSTRUCTION (default), LINE, BRANCH, COMPLEXITY, METHOD, or CLASS
+      // - A 'value' type: TOTALCOUNT, COVEREDCOUNT, MISSEDCOUNT, COVEREDRATIO (default),
+      //   or MISSEDRATIO
+      // - The 'minimum' threshold, given as a fraction or a percentage (including '%')
+      limit {
+        minimum = rootProject.ext.getMinCoverage(project.getName())
+      }
+    }
+  }
+}