Support min coverage threshold

CHANGELOG.md

@@ -1,5 +1,10 @@
 # Diff-Coverage Maven plugin
 
+## 1.2.0
+
+### Added
+- `entityCountThreshold` parameter in `violations` configuration: if the number of changed entities is below the threshold, the coverage check for that entity is skipped
+
 ## 1.1.0
 
 - Added Java 25 class files support

README.md

@@ -43,18 +43,24 @@ The plugin does the next steps:
                 </diffSource>
 
                 <!-- Optional -->
-                <violations> 
+                <violations>
                     <!-- Default 'false'. Fail build if violation rules weren't met  -->
                     <failOnViolation>true</failOnViolation>
 
                     <!-- Sets min coverage rule for: instructions, lines, branches -->
                     <minCoverage>0.7</minCoverage>
-                    
+
                     <!-- Each rule could be configured separately -->
                     <!-- Default '0.0'. If value is '0.0' then the rule is disabled -->
                     <minLines>0.1</minLines>
                     <minBranches>0.7</minBranches>
                     <minInstructions>1.0</minInstructions>
+
+                    <!-- Optional. Default '0' (disabled).
+                         If the number of changed entities is below this threshold,
+                         coverage violation checks are skipped.
+                         Useful to avoid failures on small PRs with few changed lines. -->
+                    <entityCountThreshold>20</entityCountThreshold>
                 </violations>
 
                 <!-- Optional. Exec files include pattern. By default 'build/jacoco.exec' file is used -->

src/it/violation-rule-threshold-check/diffFile.patch

@@ -0,0 +1,14 @@
+===================================================================
+--- a/src/main/java/com/test/Example.java	(revision 9e78667391946d3461759f5589b67d3a676d8ce7)
++++ b/src/main/java/com/test/Example.java	(date 1593433398791)
+@@ -5,7 +5,10 @@
+ 	public void sayHello(boolean a) {
+ 		if (a) {
+ 			System.out.println("if");
++		} else {
++			System.out.println("else");
+ 		}
++		System.out.println("return");
+ 	}
+
+ }

src/it/violation-rule-threshold-check/pom.xml

@@ -0,0 +1,71 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+
+  <groupId>jacoco</groupId>
+  <artifactId>it-threshold-check-passes</artifactId>
+  <version>1.0-SNAPSHOT</version>
+
+  <properties>
+    <maven.compiler.source>1.8</maven.compiler.source>
+    <maven.compiler.target>1.8</maven.compiler.target>
+  </properties>
+
+  <dependencies>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <version>4.13.2</version>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.jacoco</groupId>
+        <artifactId>jacoco-maven-plugin</artifactId>
+        <version>0.8.14</version>
+        <executions>
+          <execution>
+            <goals>
+              <goal>prepare-agent</goal>
+            </goals>
+          </execution>
+        </executions>
+      </plugin>
+      <plugin>
+        <groupId>io.github.surpsg</groupId>
+        <artifactId>diff-coverage-maven-plugin</artifactId>
+
+        <configuration>
+          <diffSource>
+            <file>diffFile.patch</file>
+          </diffSource>
+
+          <violations>
+            <failOnViolation>true</failOnViolation>
+            <minCoverage>1.0</minCoverage>
+            <entityCountThreshold>20</entityCountThreshold>
+          </violations>
+
+          <reports>
+            <report>
+              <type>console</type>
+              <enabled>false</enabled>
+            </report>
+          </reports>
+        </configuration>
+
+        <executions>
+          <execution>
+            <goals>
+              <goal>diffCoverage</goal>
+            </goals>
+          </execution>
+        </executions>
+      </plugin>
+    </plugins>
+  </build>
+</project>

src/it/violation-rule-threshold-check/src/main/java/com/test/Example.java

@@ -0,0 +1,14 @@
+package com.test;
+
+public class Example {
+
+	public void sayHello(boolean a) {
+		if (a) {
+			System.out.println("if");
+		} else {
+			System.out.println("else");
+		}
+		System.out.println("return");
+	}
+
+}

src/it/violation-rule-threshold-check/src/test/java/com/test/ExampleTest.java

@@ -0,0 +1,11 @@
+package com.test;
+import org.junit.Test;
+
+public class ExampleTest {
+
+	@Test
+	public void test() {
+		new Example().sayHello(true);
+	}
+
+}

src/it/violation-rule-threshold-check/verify.bsh

@@ -0,0 +1,9 @@
+import java.io.*;
+import org.codehaus.plexus.util.*;
+
+String expectedIgnoredMsg = "was ignored because threshold=20";
+
+String buildLog = FileUtils.fileRead( new File( basedir, "build.log" ) );
+if ( !buildLog.contains( expectedIgnoredMsg ) ) {
+    throw new RuntimeException( "Expected coverage violations to be ignored due to entityCountThreshold, but message not found: " + expectedIgnoredMsg );
+}

src/main/kotlin/io/github/surpsg/DiffCoverageConfiguration.kt

@@ -19,8 +19,13 @@ class ViolationsConfiguration(
     var minBranches: Double = 0.0,
     var minInstructions: Double = 0.0,
 
-    var minCoverage: Double = MIN_COVERAGE_PROPERTY_DEFAULT
-)
+    var minCoverage: Double = MIN_COVERAGE_PROPERTY_DEFAULT,
+
+    var entityCountThreshold: Int = 0
+) {
+    val entityCountThresholdOrNull: Int?
+        get() = entityCountThreshold.takeIf { it > 0 }
+}
 
 class Report(
     var type: String? = null,

src/main/kotlin/io/github/surpsg/DiffCoverageMojo.kt

@@ -114,7 +114,11 @@ class DiffCoverageMojo : AbstractMojo() {
             failOnViolation = violations.failOnViolation
             violationRules += if (isMinCoverageSet) {
                 CoverageEntity.entries.map { entity ->
-                    ViolationRule { coverageEntity = entity; minCoverageRatio = violations.minCoverage }
+                    ViolationRule {
+                        coverageEntity = entity
+                        minCoverageRatio = violations.minCoverage
+                        entityCountThreshold = violations.entityCountThresholdOrNull
+                    }
                 }
             } else {
                 buildCoverageRules()
@@ -139,7 +143,11 @@ class DiffCoverageMojo : AbstractMojo() {
     )
         .filter { it.second > 0.0 }
         .map { (entity, value) ->
-            ViolationRule { coverageEntity = entity; minCoverageRatio = value }
+            ViolationRule {
+                coverageEntity = entity
+                minCoverageRatio = value
+                entityCountThreshold = violations.entityCountThresholdOrNull
+            }
         }
         .toSet()