Add option to only show failures on test reports

docs/modules/pkl-gradle/pages/index.adoc

@@ -322,6 +322,15 @@ Default: `false` +
 Whether to ignore expected example files and generate them again.
 ====
 
+[[show-only-failed]]
+.showOnlyFailed: Property<Boolean>
+[%collapsible]
+====
+Default: `false` +
+Example: `showOnlyFailed = true` +
+Only show failed test output, hiding passing tests from the report.
+====
+
 [[power-assertions-test]]
 .powerAssertions: Property<Boolean>
 [%collapsible]
@@ -677,6 +686,14 @@ Default: `false` +
 Whether to ignore expected example files and generate them again.
 ====
 
+.showOnlyFailed: Property<Boolean>
+[%collapsible]
+====
+Default: `false` +
+Example: `showOnlyFailed = true` +
+Only show failed test output, hiding passing tests from the report.
+====
+
 Common properties:
 
 include::../partials/gradle-common-properties.adoc[]

pkl-cli/src/main/kotlin/org/pkl/cli/CliTestRunner.kt

@@ -29,7 +29,7 @@ import org.pkl.core.util.ErrorMessages
 class CliTestRunner
 @JvmOverloads
 constructor(
-  private val options: CliBaseOptions,
+  options: CliBaseOptions,
   private val testOptions: CliTestOptions,
   private val consoleWriter: Writer = System.out.writer(),
   private val errWriter: Writer = System.err.writer(),
@@ -64,13 +64,11 @@ constructor(
       var failed = false
       var isExampleWrittenFailure = true
       val moduleNames = mutableSetOf<String>()
-      val reporter = SimpleReport(useColor)
+      val reporter = SimpleReport(useColor, testOptions.showOnlyFailed)
       val allTestResults = mutableListOf<TestResults>()
 
       val junitDir = testOptions.junitDir
-      if (junitDir != null) {
-        junitDir.toFile().mkdirs()
-      }
+      junitDir?.toFile()?.mkdirs()
 
       for ((idx, moduleUri) in sources.withIndex()) {
         try {

pkl-commons-cli/src/main/kotlin/org/pkl/commons/cli/CliTestOptions.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright © 2024-2025 Apple Inc. and the Pkl project authors. All rights reserved.
+ * Copyright © 2024-2026 Apple Inc. and the Pkl project authors. All rights reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -22,4 +22,5 @@ class CliTestOptions(
   val overwrite: Boolean = false,
   val junitAggregateReports: Boolean = false,
   val junitAggregateSuiteName: String = "pkl-tests",
+  val showOnlyFailed: Boolean = false,
 )

pkl-commons-cli/src/main/kotlin/org/pkl/commons/cli/commands/TestOptions.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright © 2024-2025 Apple Inc. and the Pkl project authors. All rights reserved.
+ * Copyright © 2024-2026 Apple Inc. and the Pkl project authors. All rights reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -51,7 +51,16 @@ class TestOptions : OptionGroup() {
   private val overwrite: Boolean by
     option(names = arrayOf("--overwrite"), help = "Force generation of expected examples.").flag()
 
+  private val showOnlyFailed: Boolean by
+    option(names = arrayOf("--show-only-failed"), help = "Only show failed test output.").flag()
+
   val cliTestOptions: CliTestOptions by lazy {
-    CliTestOptions(junitReportDir, overwrite, junitAggregateReports, junitAggregateSuiteName)
+    CliTestOptions(
+      junitReportDir,
+      overwrite,
+      junitAggregateReports,
+      junitAggregateSuiteName,
+      showOnlyFailed,
+    )
   }
 }

pkl-core/src/main/java/org/pkl/core/stdlib/test/report/SimpleReport.java

@@ -1,5 +1,5 @@
 /*
- * Copyright © 2024-2025 Apple Inc. and the Pkl project authors. All rights reserved.
+ * Copyright © 2024-2026 Apple Inc. and the Pkl project authors. All rights reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -36,9 +36,11 @@ public final class SimpleReport implements TestReport {
   private static final String failingMark = "✘ ";
 
   private final boolean useColor;
+  private final boolean showOnlyFailed;
 
-  public SimpleReport(boolean useColor) {
+  public SimpleReport(boolean useColor, boolean showOnlyFailed) {
     this.useColor = useColor;
+    this.showOnlyFailed = showOnlyFailed;
   }
 
   @Override
@@ -92,10 +94,13 @@ public void summarize(List<TestResults> allTestResults, Writer writer) throws IO
   }
 
   private void reportResults(TestSectionResults section, AnsiStringBuilder builder) {
-    if (!section.results().isEmpty()) {
+    var results =
+        showOnlyFailed
+            ? section.results().stream().filter(TestResult::isFailure).toList()
+            : section.results();
+    if (!results.isEmpty()) {
       builder.append("  ").append(section.name()).append('\n');
-      StringUtils.joinToStringBuilder(
-          builder, section.results(), "\n", res -> reportResult(res, builder));
+      StringUtils.joinToStringBuilder(builder, results, "\n", res -> reportResult(res, builder));
       builder.append('\n');
     }
   }

pkl-core/src/test/kotlin/org/pkl/core/stdlib/SimpleReportTest.kt

@@ -60,7 +60,7 @@ class SimpleReportTest {
     val testResults = listOf(resultsBuilder.build())
 
     val writer = StringWriter()
-    val simpleReport = SimpleReport(false)
+    val simpleReport = SimpleReport(false, false)
     simpleReport.summarize(testResults, writer)
 
     val expectedOutput =
@@ -71,4 +71,70 @@ class SimpleReportTest {
 
     assertThat(writer.toString().trimIndent()).isEqualTo(expectedOutput)
   }
+
+  @Test
+  fun `report with showOnlyFailed filters out passing tests`() {
+    val resultsBuilder = TestResults.Builder("module1", "module1")
+    resultsBuilder.setFactsSection(
+      TestSectionResults(
+        TestResults.TestSectionName.FACTS,
+        listOf(
+          TestResult("passing fact", 1, emptyList(), emptyList(), false),
+          TestResult(
+            "failing fact",
+            1,
+            listOf(TestResults.Failure("Fact Failure", "failed")),
+            emptyList(),
+            false,
+          ),
+        ),
+      )
+    )
+    resultsBuilder.setExamplesSection(
+      TestSectionResults(
+        TestResults.TestSectionName.EXAMPLES,
+        listOf(TestResult("passing example", 1, emptyList(), emptyList(), false)),
+      )
+    )
+    val testResults = resultsBuilder.build()
+
+    val writer = StringWriter()
+    val simpleReport = SimpleReport(false, true)
+    simpleReport.report(testResults, writer)
+
+    val output = writer.toString()
+    assertThat(output).contains("failing fact")
+    assertThat(output).doesNotContain("passing fact")
+    assertThat(output).doesNotContain("passing example")
+    assertThat(output).doesNotContain("examples")
+  }
+
+  @Test
+  fun `report without showOnlyFailed includes all tests`() {
+    val resultsBuilder = TestResults.Builder("module1", "module1")
+    resultsBuilder.setFactsSection(
+      TestSectionResults(
+        TestResults.TestSectionName.FACTS,
+        listOf(
+          TestResult("passing fact", 1, emptyList(), emptyList(), false),
+          TestResult(
+            "failing fact",
+            1,
+            listOf(TestResults.Failure("Fact Failure", "failed")),
+            emptyList(),
+            false,
+          ),
+        ),
+      )
+    )
+    val testResults = resultsBuilder.build()
+
+    val writer = StringWriter()
+    val simpleReport = SimpleReport(false, false)
+    simpleReport.report(testResults, writer)
+
+    val output = writer.toString()
+    assertThat(output).contains("passing fact")
+    assertThat(output).contains("failing fact")
+  }
 }

pkl-gradle/src/main/java/org/pkl/gradle/PklPlugin.java

@@ -98,6 +98,7 @@ private void configureProjectPackageTasks(
           spec.getOutputPath()
               .convention(project.getLayout().getBuildDirectory().dir("generated/pkl/packages"));
           spec.getOverwrite().convention(false);
+          spec.getShowOnlyFailed().convention(false);
           var packageTask = createTask(project, ProjectPackageTask.class, spec);
           packageTask.configure(
               task -> {
@@ -106,6 +107,7 @@ private void configureProjectPackageTasks(
                 task.getSkipPublishCheck().set(spec.getSkipPublishCheck());
                 task.getJunitReportsDir().set(spec.getJunitReportsDir());
                 task.getOverwrite().set(spec.getOverwrite());
+                task.getShowOnlyFailed().set(spec.getShowOnlyFailed());
               });
           project
               .getPluginManager()
@@ -274,12 +276,14 @@ private void configureTestTasks(Project project, NamedDomainObjectContainer<Test
           configureBaseSpec(project, spec);
 
           spec.getOverwrite().convention(false);
+          spec.getShowOnlyFailed().convention(false);
 
           var testTask = createModulesTask(project, TestTask.class, spec);
           testTask.configure(
               task -> {
                 task.getJunitReportsDir().set(spec.getJunitReportsDir());
                 task.getOverwrite().set(spec.getOverwrite());
+                task.getShowOnlyFailed().set(spec.getShowOnlyFailed());
               });
 
           project

pkl-gradle/src/main/java/org/pkl/gradle/spec/ProjectPackageSpec.java

@@ -1,5 +1,5 @@
 /*
- * Copyright © 2024 Apple Inc. and the Pkl project authors. All rights reserved.
+ * Copyright © 2024-2026 Apple Inc. and the Pkl project authors. All rights reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -29,4 +29,6 @@ public interface ProjectPackageSpec extends BasePklSpec {
   Property<Boolean> getOverwrite();
 
   Property<Boolean> getSkipPublishCheck();
+
+  Property<Boolean> getShowOnlyFailed();
 }

pkl-gradle/src/main/java/org/pkl/gradle/spec/TestSpec.java

@@ -1,5 +1,5 @@
 /*
- * Copyright © 2024 Apple Inc. and the Pkl project authors. All rights reserved.
+ * Copyright © 2024-2026 Apple Inc. and the Pkl project authors. All rights reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -22,4 +22,6 @@ public interface TestSpec extends ModulesSpec {
   DirectoryProperty getJunitReportsDir();
 
   Property<Boolean> getOverwrite();
+
+  Property<Boolean> getShowOnlyFailed();
 }

pkl-gradle/src/main/java/org/pkl/gradle/task/ProjectPackageTask.java

@@ -60,6 +60,10 @@ public abstract class ProjectPackageTask extends BasePklTask {
   @Optional
   public abstract Property<Boolean> getSkipPublishCheck();
 
+  @Input
+  @Optional
+  public abstract Property<Boolean> getShowOnlyFailed();
+
   public ProjectPackageTask() {
     this.getJunitAggregateSuiteName().convention("pkl-tests");
   }
@@ -81,7 +85,8 @@ protected void doRunTask() {
                 mapAndGetOrNull(getJunitReportsDir(), it -> it.getAsFile().toPath()),
                 getOverwrite().get(),
                 getJunitAggregateReports().getOrElse(false),
-                getJunitAggregateSuiteName().get()),
+                getJunitAggregateSuiteName().get(),
+                getShowOnlyFailed().getOrElse(false)),
             getOutputPath().get().getAsFile().getAbsolutePath(),
             getSkipPublishCheck().getOrElse(false),
             new PrintWriter(System.out),

pkl-gradle/src/main/java/org/pkl/gradle/task/TestTask.java

@@ -41,6 +41,10 @@ public abstract class TestTask extends ModulesTask {
   @Input
   public abstract Property<Boolean> getOverwrite();
 
+  @Input
+  @Optional
+  public abstract Property<Boolean> getShowOnlyFailed();
+
   public TestTask() {
     this.getJunitAggregateSuiteName().convention("pkl-tests");
     this.getPowerAssertions().convention(true);
@@ -54,7 +58,8 @@ protected void doRunTask() {
                 mapAndGetOrNull(getJunitReportsDir(), it -> it.getAsFile().toPath()),
                 getOverwrite().get(),
                 getJunitAggregateReports().getOrElse(false),
-                getJunitAggregateSuiteName().get()),
+                getJunitAggregateSuiteName().get(),
+                getShowOnlyFailed().getOrElse(false)),
             new PrintWriter(System.out),
             new PrintWriter(System.err))
         .run();