Add gradle diffCoverage report (#248)

* Add gradle diffCoverage report

Signed-off-by: Daniel Widdis <[email protected]>

* Document usage in CONTRIBUTING

Signed-off-by: Daniel Widdis <[email protected]>

* Fail on violation, match thresholds to AD project

Signed-off-by: Daniel Widdis <[email protected]>

* Work around JGit uncommitted file issue by executing git diff

Signed-off-by: Daniel Widdis <[email protected]>

Signed-off-by: Daniel Widdis <[email protected]>

Author: dbwiddis

.github/workflows/build.yml

@@ -12,7 +12,9 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v3
-
+        with:
+          # needed for git diff to find main branch
+          fetch-depth: "0"
       - name: Spotless Check
         run: ./gradlew spotlessCheck
   check:
@@ -27,6 +29,9 @@ jobs:
         run: |
           ./gradlew publishToMavenLocal
       - uses: actions/checkout@v3
+        with:
+          # needed for git diff to find main branch
+          fetch-depth: "0"
       - name: Set up JDK 11
         uses: actions/setup-java@v2
         with:

CONTRIBUTING.md

@@ -1,13 +1,14 @@
-- [Contributing to OpenSearch-SDK-Java](#contributing-to-opensearch-sdk-java)
+- [Contributing to OpenSearch SDK for Java](#contributing-to-opensearch-sdk-for-java)
   - [First Things First](#first-things-first)
   - [Ways to Contribute](#ways-to-contribute)
     - [Bug Reports](#bug-reports)
     - [Feature Requests](#feature-requests)
     - [Contributing Code](#contributing-code)
   - [Developer Certificate of Origin](#developer-certificate-of-origin)
+  - [Code Coverage](#code-coverage)
   - [Review Process](#review-process)
 
-# Contributing to OpenSearch-SDK
+# Contributing to OpenSearch SDK for Java
 
 OpenSearch-SDK is a community project that is built and maintained by people just like **you**. We're glad you're interested in helping out. There are several different ways you can do it, but before we talk about that, let's talk about how to get started.
 
@@ -77,6 +78,12 @@ Signed-off-by: Jane Smith <[email protected]>
 ```
 You may type this line on your own when writing your commit messages. However, if your user.name and user.email are set in your git configs, you can use `-s` or `--signoff` to add the `Signed-off-by` line to the end of the commit message.
 
+## Code Coverage
+
+Any new functionality requires testing. Your PR will trigger an automatic assessment of the code coverage of the lines you've added. You should add unit and/or integration tests to exercise as much of your new code as possible.
+
+If you'd like to preview your coverage before submitting your PR, to identify lines of code which are not tested, you may run `./gradlew diffCoverage` and review the report available in the project build directory at `build/reports/jacoco/diffCoverage/html/index.html`.
+
 ## Review Process
 
 We deeply appreciate everyone who takes the time to make a contribution. We will review all contributions as quickly as possible. As a reminder, [opening an issue](https://github.com/opensearch-project/opensearch-sdk-java/issues/new/choose) discussing your change before you make it is the best way to smooth the PR process. This will prevent a rejection because someone else is already working on the problem, or because the solution is incompatible with the architectural direction.

build.gradle

@@ -9,10 +9,13 @@
  * GitHub history for details.
  */
 
+import java.nio.file.Files
+
 plugins {
     id 'java'
     id "com.diffplug.spotless" version "6.11.0" apply false
     id 'jacoco'
+    id "com.form.diff-coverage" version "0.9.5"
 }
 
 
@@ -147,3 +150,37 @@ jacocoTestReport {
         xml.required = true
     }
 }
+
+// Get uncommitted files via git diff
+// https://github.com/form-com/diff-coverage-gradle/issues/73
+ext.createDiffFile = { ->
+    def file = Files.createTempFile(URLEncoder.encode(project.name, 'UTF-8'), '.diff').toFile()
+    def diffBase = 'refs/remotes/origin/main'
+    if (System.getenv('CI')) {
+        diffBase = 'origin/' + System.getenv('GITHUB_BASE_REF')
+    }
+    file.withOutputStream { out ->
+        exec {
+            commandLine 'git', 'diff', '--no-color', '--minimal', diffBase
+            standardOutput = out
+        }
+    }
+    return file
+}
+
+diffCoverageReport {
+    afterEvaluate {
+        diffSource.file = createDiffFile()
+    }
+
+    // View report at build/reports/jacoco/diffCoverage/html/index.html
+    reports {
+        html = true
+    }
+
+    violationRules {
+        minBranches = 0.60
+        minLines = 0.75
+        failOnViolation = true
+    }
+}