Align JVM- and KLib-validation behavior for empty projects

Also, reworked error reporting for the compare task.

src/functionalTest/kotlin/kotlinx/validation/test/DefaultConfigTests.kt

@@ -26,8 +26,13 @@ internal class DefaultConfigTests : BaseKotlinGradleTest() {
             }
         }
 
+        val projectName = rootProjectDir.name
         runner.buildAndFail().apply {
-            assertTrue { output.contains("Please ensure that ':apiDump' was executed") }
+            Assertions.assertThat(output).contains(
+                "Expected file with API declarations 'api/$projectName.api' does not exist."
+            ).contains(
+                "Please ensure that ':apiDump' was executed in order to get an API dump to compare the build against"
+            )
             assertTaskFailure(":apiCheck")
         }
     }

src/functionalTest/kotlin/kotlinx/validation/test/KlibVerificationTests.kt

@@ -14,6 +14,7 @@ import org.gradle.testkit.runner.BuildResult
 import org.jetbrains.kotlin.konan.target.HostManager
 import org.jetbrains.kotlin.konan.target.KonanTarget
 import org.jetbrains.kotlin.utils.addToStdlib.butIf
+import org.junit.Assert
 import org.junit.Assume
 import org.junit.Test
 import java.io.File
@@ -49,27 +50,32 @@ internal class KlibVerificationTests : BaseKotlinGradleTest() {
             resolve("/examples/gradle/base/withNativePlugin.gradle.kts")
         }
     }
+
     private fun BaseKotlinScope.additionalBuildConfig(config: String) {
         buildGradleKts {
             resolve(config)
         }
     }
+
     private fun BaseKotlinScope.addToSrcSet(pathTestFile: String, sourceSet: String = "commonMain") {
         val fileName = Paths.get(pathTestFile).fileName.toString()
         kotlin(fileName, sourceSet) {
             resolve(pathTestFile)
         }
     }
+
     private fun BaseKotlinScope.runApiCheck() {
         runner {
             arguments.add(":apiCheck")
         }
     }
+
     private fun BaseKotlinScope.runApiDump() {
         runner {
             arguments.add(":apiDump")
         }
     }
+
     private fun assertApiCheckPassed(buildResult: BuildResult) {
         buildResult.assertTaskSuccess(":apiCheck")
     }
@@ -581,8 +587,10 @@ internal class KlibVerificationTests : BaseKotlinGradleTest() {
         checkKlibDump(runner.build(), "/examples/classes/AnotherBuildConfig.klib.dump")
 
         // Update the source file by adding a declaration
-        val updatedSourceFile = File(this::class.java.getResource(
-            "/examples/classes/AnotherBuildConfigModified.kt")!!.toURI()
+        val updatedSourceFile = File(
+            this::class.java.getResource(
+                "/examples/classes/AnotherBuildConfigModified.kt"
+            )!!.toURI()
         )
         val existingSource = runner.projectDir.resolve(
             "src/commonMain/kotlin/AnotherBuildConfig.kt"
@@ -602,8 +610,10 @@ internal class KlibVerificationTests : BaseKotlinGradleTest() {
         checkKlibDump(runner.build(), "/examples/classes/AnotherBuildConfig.klib.dump")
 
         // Update the source file by adding a declaration
-        val updatedSourceFile = File(this::class.java.getResource(
-            "/examples/classes/AnotherBuildConfigLinuxArm64.kt")!!.toURI()
+        val updatedSourceFile = File(
+            this::class.java.getResource(
+                "/examples/classes/AnotherBuildConfigLinuxArm64.kt"
+            )!!.toURI()
         )
         val existingSource = runner.projectDir.resolve(
             "src/linuxArm64Main/kotlin/AnotherBuildConfigLinuxArm64.kt"
@@ -627,8 +637,10 @@ internal class KlibVerificationTests : BaseKotlinGradleTest() {
         assertApiCheckPassed(runner.build())
 
         // Update the source file by adding a declaration
-        val updatedSourceFile = File(this::class.java.getResource(
-            "/examples/classes/AnotherBuildConfigModified.kt")!!.toURI()
+        val updatedSourceFile = File(
+            this::class.java.getResource(
+                "/examples/classes/AnotherBuildConfigModified.kt"
+            )!!.toURI()
         )
         val existingSource = runner.projectDir.resolve(
             "src/commonMain/kotlin/AnotherBuildConfig.kt"
@@ -701,13 +713,18 @@ internal class KlibVerificationTests : BaseKotlinGradleTest() {
     }
 
     @Test
-    fun `apiCheck should not fail for empty project`() {
+    fun `apiCheck should fail for empty project`() {
         val runner = test {
             baseProjectSetting()
             addToSrcSet("/examples/classes/AnotherBuildConfig.kt", sourceSet = "commonTest")
             runApiCheck()
         }
-        runner.build()
+        runner.buildAndFail().apply {
+            assertTaskFailure(":klibApiExtractForValidation")
+            Assertions.assertThat(output).contains(
+                "File with project's API declarations 'api/testproject.klib.api' does not exist."
+            )
+        }
     }
 
     @Test

src/main/kotlin/KotlinApiCompareTask.kt

@@ -14,15 +14,13 @@ import org.gradle.api.file.RegularFileProperty
 import org.gradle.api.tasks.*
 
 @CacheableTask
-public open class KotlinApiCompareTask @Inject constructor(): DefaultTask() {
+public open class KotlinApiCompareTask @Inject constructor() : DefaultTask() {
 
-    @get:InputFiles
-    @get:SkipWhenEmpty
+    @get:InputFiles // don't fail the task if file does not exist, instead print custom error message from verify()
     @get:PathSensitive(PathSensitivity.RELATIVE)
     public val projectApiFile: RegularFileProperty = project.objects.fileProperty()
 
-    @get:InputFiles
-    @get:SkipWhenEmpty
+    @get:InputFiles // don't fail the task if file does not exist, instead print custom error message from verify()
     @get:PathSensitive(PathSensitivity.RELATIVE)
     public val generatedApiFile: RegularFileProperty = project.objects.fileProperty()
 
@@ -35,51 +33,46 @@ public open class KotlinApiCompareTask @Inject constructor(): DefaultTask() {
         val projectApiFile = projectApiFile.get().asFile
         val generatedApiFile = generatedApiFile.get().asFile
 
-        val projectApiDir = projectApiFile.parentFile
-        if (!projectApiDir.exists()) {
-            error("Expected folder with API declarations '$projectApiDir' does not exist.\n" +
-                    "Please ensure that ':apiDump' was executed in order to get API dump to compare the build against")
-        }
-        val buildApiDir = generatedApiFile.parentFile
-        if (!buildApiDir.exists()) {
-            error("Expected folder with generate API declarations '$buildApiDir' does not exist.")
-        }
-        val subject = projectName
-
         if (!projectApiFile.exists()) {
-            error("File ${projectApiFile.name} is missing from ${projectApiDir.relativeDirPath()}, please run " +
-                    ":$subject:apiDump task to generate one")
+            error(
+                "Expected file with API declarations '${projectApiFile.relativeTo(rootDir)}' does not exist.\n" +
+                        "Please ensure that ':apiDump' was executed in order to get " +
+                        "an API dump to compare the build against"
+            )
         }
         if (!generatedApiFile.exists()) {
-            error("File ${generatedApiFile.name} is missing from dump results.")
+            error(
+                "Expected file with generated API declarations '${generatedApiFile.relativeTo(rootDir)}'" +
+                        " does not exist."
+            )
         }
 
-        // Normalize case-sensitivity
         val diffSet = mutableSetOf<String>()
         val diff = compareFiles(projectApiFile, generatedApiFile)
         if (diff != null) diffSet.add(diff)
         if (diffSet.isNotEmpty()) {
             val diffText = diffSet.joinToString("\n\n")
-            error("API check failed for project $subject.\n$diffText\n\n You can run :$subject:apiDump task to overwrite API declarations")
+            val subject = projectName
+            error(
+                "API check failed for project $subject.\n$diffText\n\n" +
+                        "You can run :$subject:apiDump task to overwrite API declarations"
+            )
         }
     }
 
-    private fun File.relativeDirPath(): String {
-        return toRelativeString(rootDir) + File.separator
-    }
-
     private fun compareFiles(checkFile: File, builtFile: File): String? {
         val checkText = checkFile.readText()
         val builtText = builtFile.readText()
 
-        // We don't compare full text because newlines on Windows & Linux/macOS are different
+        // We don't compare a full text because newlines on Windows & Linux/macOS are different
         val checkLines = checkText.lines()
         val builtLines = builtText.lines()
         if (checkLines == builtLines)
             return null
 
         val patch = DiffUtils.diff(checkLines, builtLines)
-        val diff = UnifiedDiffUtils.generateUnifiedDiff(checkFile.toString(), builtFile.toString(), checkLines, patch, 3)
+        val diff =
+            UnifiedDiffUtils.generateUnifiedDiff(checkFile.toString(), builtFile.toString(), checkLines, patch, 3)
         return diff.joinToString("\n")
     }
 }

src/main/kotlin/KotlinKlibExtractAbiTask.kt

@@ -25,7 +25,7 @@ public abstract class KotlinKlibExtractAbiTask : DefaultTask() {
     /**
      * Merged KLib dump that should be filtered by this task.
      */
-    @get:InputFiles
+    @get:InputFiles // don't fail the task if file does not exist, instead print custom error message from generate()
     @get:PathSensitive(PathSensitivity.RELATIVE)
     public abstract val inputAbiFile: RegularFileProperty
 
@@ -47,13 +47,18 @@ public abstract class KotlinKlibExtractAbiTask : DefaultTask() {
     @get:OutputFile
     public abstract val outputAbiFile: RegularFileProperty
 
+    private val rootDir = project.rootDir
+
     @OptIn(ExperimentalBCVApi::class)
     @TaskAction
     internal fun generate() {
         val inputFile = inputAbiFile.asFile.get()
-        if (!inputFile.exists()) return
+        if (!inputFile.exists()) {
+            error("File with project's API declarations '${inputFile.relativeTo(rootDir)}' does not exist.\n" +
+                    "Please ensure that ':apiDump' was executed in order to get API dump to compare the build against")
+        }
         if (inputFile.length() == 0L) {
-            error("Project ABI file $inputAbiFile is empty.")
+            error("Project ABI file ${inputFile.relativeTo(rootDir)} is empty.")
         }
         val dump = KlibDump.from(inputFile)
         val enabledTargets = requiredTargets.get().map(KlibTarget::targetName).toSet()