Keep Kotlin compile configs of composite builds apart

The Gradle plugin named each Kotlin config file after the sanitized task
path. Task paths are only unique within one build, so the root build and
an included build both wrote -compileKotlin.txt and the later one
replaced the earlier, dropping its sources from the index. Sanitizing
also mapped :a-b:compileKotlin and 🅰️b:compileKotlin to the same name.

Name the file after a hash of the build's root directory and the task
path instead.

Amp-Thread-ID: https://ampcode.com/threads/T-01a1a6a2-f2b0-775c-a192-e5d11290c493
Co-authored-by: Christoph Hegemann <christoph.hegemann@sourcegraph.com>

Author: ampagent

scip-gradle-plugin/src/main/java/org/scip_code/scip_java/gradle/ScipGradlePlugin.java

@@ -1,11 +1,14 @@
 package org.scip_code.scip_java.gradle;
 
 import java.io.File;
+import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
+import java.security.MessageDigest;
 import java.util.ArrayList;
 import java.util.HashSet;
+import java.util.HexFormat;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -271,7 +274,8 @@ private static Set<String> addJavacPlugin(Project project, Object javacPluginDep
   }
 
   /**
-   * Dumps the sources and classpath of a Kotlin compile task to {@code kotlin-configs/<task>.txt}.
+   * Dumps the sources and classpath of a Kotlin compile task to {@code
+   * kotlin-configs/<task>-<hash>.txt}.
    */
   private static void writeKotlinConfig(Task task, String sourceRoot, String targetRoot) {
     try {
@@ -317,7 +321,14 @@ private static void writeKotlinConfig(Task task, String sourceRoot, String targe
 
       Path configDir = Paths.get(targetRoot, "kotlin-configs");
       Files.createDirectories(configDir);
-      String fileName = task.getPath().replaceAll("[^A-Za-z0-9]", "-") + ".txt";
+      // Task paths are only unique within one build, and every build of a
+      // composite (included builds, buildSrc) writes here, so the build's
+      // root directory is part of the identity. Hashing, unlike sanitizing,
+      // keeps ":a-b:x" and ":a:b:x" apart; NUL cannot occur in a path.
+      String identity = task.getProject().getRootDir().getAbsolutePath() + "\0" + task.getPath();
+      byte[] hash =
+          MessageDigest.getInstance("SHA-256").digest(identity.getBytes(StandardCharsets.UTF_8));
+      String fileName = task.getName() + "-" + HexFormat.of().formatHex(hash, 0, 8) + ".txt";
       Files.write(configDir.resolve(fileName), lines);
     } catch (Exception exc) {
       throw new RuntimeException(

scip-java/src/test/kotlin/tests/GradleBuildToolTest.kt

@@ -204,6 +204,11 @@ class GradleBuildToolTest : BuildToolHarness() {
                 runs = 2,
             )
         )
+        // Regression test: Kotlin compile tasks whose paths are equal in different
+        // builds of a composite (`:compileKotlin` in the root and included build),
+        // or equal after sanitizing (`:a-b` and `:a:b`), overwrote each other's
+        // configs, so only one of their sources was indexed.
+        add(checkGradleBuild("kotlin-composite", "gradle/kotlin-composite", expectedScipFiles = 4))
         add(
             checkGradleBuild(
                 "implementation-deps",

scip-java/src/test/resources/fixtures/gradle/kotlin-composite/a-b/build.gradle

@@ -0,0 +1,3 @@
+plugins {
+    id 'org.jetbrains.kotlin.jvm'
+}

scip-java/src/test/resources/fixtures/gradle/kotlin-composite/a-b/src/main/kotlin/ab/Dashed.kt

@@ -0,0 +1,2 @@
+package ab
+object Dashed {}

scip-java/src/test/resources/fixtures/gradle/kotlin-composite/a/b/build.gradle

@@ -0,0 +1,3 @@
+plugins {
+    id 'org.jetbrains.kotlin.jvm'
+}

scip-java/src/test/resources/fixtures/gradle/kotlin-composite/a/b/src/main/kotlin/ab/Nested.kt

@@ -0,0 +1,2 @@
+package ab
+object Nested {}

scip-java/src/test/resources/fixtures/gradle/kotlin-composite/build.gradle

@@ -0,0 +1,12 @@
+plugins {
+    id 'org.jetbrains.kotlin.jvm' version '2.4.0'
+}
+allprojects {
+    repositories {
+        mavenCentral()
+    }
+}
+// `scipCompileAll` only runs tasks of the root build.
+tasks.named('compileKotlin') {
+    dependsOn gradle.includedBuild('included').task(':compileKotlin')
+}

scip-java/src/test/resources/fixtures/gradle/kotlin-composite/included/build.gradle

@@ -0,0 +1,6 @@
+plugins {
+    id 'org.jetbrains.kotlin.jvm' version '2.4.0'
+}
+repositories {
+    mavenCentral()
+}

scip-java/src/test/resources/fixtures/gradle/kotlin-composite/included/settings.gradle

@@ -0,0 +1 @@
+rootProject.name = 'included'

scip-java/src/test/resources/fixtures/gradle/kotlin-composite/included/src/main/kotlin/included/Included.kt

@@ -0,0 +1,2 @@
+package included
+object Included {}