Add custom decompiler tests. Includes test utils for creating buildSrc plugins.

src/test/groovy/net/fabricmc/loom/test/LoomTestConstants.groovy

@@ -28,7 +28,7 @@ import org.gradle.util.GradleVersion
 
 class LoomTestConstants {
     public final static String DEFAULT_GRADLE = GradleVersion.current().getVersion()
-    public final static String PRE_RELEASE_GRADLE = "7.5-20220116010338+0000"
+    public final static String PRE_RELEASE_GRADLE = "7.5-20220122232041+0000"
 
     public final static String[] STANDARD_TEST_VERSIONS = [DEFAULT_GRADLE, PRE_RELEASE_GRADLE]
 }

src/test/groovy/net/fabricmc/loom/test/integration/DecompileTest.groovy

@@ -50,4 +50,28 @@ class DecompileTest extends Specification implements GradleProjectTestTrait {
 			'cfr' 			| "genSourcesWithCfr"				| DEFAULT_GRADLE
 			'cfr' 			| "genSourcesWithCfr"				| PRE_RELEASE_GRADLE
 	}
+
+	@Unroll
+	def "custom decompiler (gradle #version)"() {
+		setup:
+			def gradle = gradleProject(project: "minimalBase", version: version)
+			gradle.buildSrc("decompile")
+			gradle.buildGradle << '''
+                dependencies {
+                    minecraft "com.mojang:minecraft:1.18.1"
+                    mappings "net.fabricmc:yarn:1.18.1+build.18:v2"
+                }
+            '''
+		when:
+			def result = gradle.run(task: "genSourcesWithCustom")
+
+		then:
+			result.task(":genSourcesWithCustom").outcome == SUCCESS
+			result.task(":preDecompile").outcome == SUCCESS
+			result.output.contains("Writing test file")
+			result.output.contains("Running custom decompiler")
+
+		where:
+			version << STANDARD_TEST_VERSIONS
+	}
 }

src/test/groovy/net/fabricmc/loom/test/integration/buildSrc/decompile/CustomDecompiler.groovy

@@ -0,0 +1,37 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2022 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.test.integration.buildSrc.decompile
+
+import net.fabricmc.loom.api.decompilers.DecompilationMetadata
+import net.fabricmc.loom.api.decompilers.LoomDecompiler
+
+import java.nio.file.Path
+
+class CustomDecompiler implements LoomDecompiler {
+    @Override
+    void decompile(Path compiledJar, Path sourcesDestination, Path linemapDestination, DecompilationMetadata metaData) {
+        println("Running custom decompiler")
+    }
+}

src/test/groovy/net/fabricmc/loom/test/integration/buildSrc/decompile/PreDecompileTask.groovy

@@ -0,0 +1,41 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2022 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.test.integration.buildSrc.decompile
+
+import org.gradle.api.DefaultTask
+import org.gradle.api.file.RegularFileProperty
+import org.gradle.api.tasks.OutputFile
+import org.gradle.api.tasks.TaskAction
+
+abstract class PreDecompileTask extends DefaultTask {
+    @OutputFile
+    abstract RegularFileProperty getOutputFile()
+
+    @TaskAction
+    def run() {
+        println("Writing test file")
+        getOutputFile().asFile.get().text = "Test"
+    }
+}

src/test/groovy/net/fabricmc/loom/test/integration/buildSrc/decompile/TestPlugin.groovy

@@ -0,0 +1,49 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2022 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.test.integration.buildSrc.decompile
+
+import net.fabricmc.loom.LoomGradleExtension
+import org.gradle.api.Plugin
+import org.gradle.api.Project
+
+class TestPlugin implements Plugin<Project> {
+    @Override
+    void apply(Project project) {
+        println("Test plugin")
+        def extension = LoomGradleExtension.get(project)
+
+        def preDecompileTask = project.tasks.register("preDecompile", PreDecompileTask.class) {
+            outputFile = project.file("output.txt")
+        }
+
+        extension.decompilerOptions.register("custom") {
+            decompilerClassName.set(CustomDecompiler.class.name)
+
+            // BuiltBy shouldn't be required, but for some reason it is? Any ideas?
+            classpath.from(preDecompileTask)
+            classpath.builtBy(preDecompileTask)
+        }
+    }
+}

src/test/groovy/net/fabricmc/loom/test/util/GradleProjectTestTrait.groovy

@@ -27,6 +27,7 @@ package net.fabricmc.loom.test.util
 import groovy.transform.Immutable
 import net.fabricmc.loom.test.LoomTestConstants
 import net.fabricmc.loom.util.ZipUtils
+import org.apache.commons.io.FileUtils
 import org.gradle.testkit.runner.BuildResult
 import org.gradle.testkit.runner.GradleRunner
 import spock.lang.Shared
@@ -141,8 +142,8 @@ trait GradleProjectTestTrait {
         private String gradleVersion
         private String projectDir
         private String gradleHomeDir
-
         private String warningMode
+        private boolean useBuildSrc
 
         BuildResult run(Map options) {
             // Setup the system props to tell loom that its running in a test env
@@ -167,6 +168,10 @@ trait GradleProjectTestTrait {
 
             runner.withArguments(args as String[])
 
+            if (useBuildSrc) {
+                writeBuildSrcDeps(runner)
+            }
+
             return options.expectFailure ? runner.buildAndFail() : runner.build()
         }
 
@@ -228,5 +233,65 @@ trait GradleProjectTestTrait {
         File getGeneratedSources(String mappings) {
             return new File(getGradleHomeDir(), "caches/fabric-loom/${mappings}/minecraft-merged-named-sources.jar")
         }
+
+        void buildSrc(String name) {
+            useBuildSrc = true
+
+            def buildSrcDir = new File(projectDir, "buildSrc")
+            buildSrcDir.mkdirs()
+
+            def pluginClass = "net.fabricmc.loom.test.integration.buildSrc.${name}.TestPlugin"
+            new File(buildSrcDir, "build.gradle") << """
+                plugins {
+                    id 'groovy-gradle-plugin'
+                    id 'groovy'
+                }
+
+                gradlePlugin {
+                    plugins {
+                        simplePlugin {
+                            id = 'loom-test-plugin'
+                            implementationClass = '${pluginClass}'
+                        }
+                    }
+                }
+            """
+
+            new File(buildSrcDir, "settings.gradle") << '''
+                rootProject.name='loom-test-plugin'
+            '''
+
+            // Patch the new plugin into the end of the plugins block
+            def matcher = buildGradle.text =~ /(?s)plugins \{(?<ids>.*)}/
+            assert matcher.find()
+            def ids = matcher.group("ids")
+
+            def pluginBlock = """
+                plugins {
+                    ${ids}
+                    id 'loom-test-plugin'
+                }
+            """
+
+            buildGradle.text = buildGradle.text.replaceAll("(?s)(plugins \\{.*})", pluginBlock)
+
+            def sourceSrc = new File("src/test/groovy/net/fabricmc/loom/test/integration/buildSrc/" + name)
+            def targetSrc = new File(buildSrcDir, "src/main/groovy/net/fabricmc/loom/test/integration/buildSrc/" + name)
+
+            FileUtils.copyDirectory(sourceSrc, targetSrc)
+        }
+
+        void writeBuildSrcDeps(GradleRunner runner) {
+            def dependencies = ""
+            runner.pluginClasspath.forEach { File file ->
+                dependencies += "implementation files('${file.absolutePath.replace("\\", "\\\\")}')\n"
+            }
+
+            new File(projectDir, "buildSrc/build.gradle") << """
+                dependencies {
+                    ${dependencies}
+                }
+            """
+        }
     }
 }