Add Maven build config

.github/workflows/ci.yml

@@ -22,7 +22,7 @@ jobs:
       - uses: DeterminateSystems/magic-nix-cache-action@v13
 
       - name: Main project tests
-        run: nix develop .#jdk${{ matrix.java }} --command gradle test --no-daemon
+        run: nix develop .#jdk${{ matrix.java }} --command mvn --batch-mode test
 
   docker_test:
     runs-on: ubuntu-latest
@@ -62,6 +62,7 @@ jobs:
 
       - uses: DeterminateSystems/magic-nix-cache-action@v13
 
+      - run: nix develop --command mvn --batch-mode -DskipTests install
       - run: nix develop --command bazelisk build //... --//scip-javac:enabled=true
       - run: nix develop --command bazelisk run scip-aggregator:bazel -- --sourceroot "$PWD"
       - run: du -h index.scip
@@ -83,8 +84,8 @@ jobs:
 
       - uses: DeterminateSystems/magic-nix-cache-action@v13
 
-      - run: nix develop --command gradle :scip-java:installDist --no-daemon
-      - run: echo "$PWD/scip-java/build/install/scip-java/bin" >> "$GITHUB_PATH"
+      - run: nix develop --command mvn --batch-mode -DskipTests install
+      - run: echo "$PWD/scip-java/target/install/scip-java/bin" >> "$GITHUB_PATH"
       - name: Auto-index scip-java codebase
         run: |
           # shellcheck disable=SC2016
@@ -113,10 +114,10 @@ jobs:
       - uses: DeterminateSystems/magic-nix-cache-action@v13
 
       - name: scip-kotlinc tests
-        run: nix develop --command gradle :scip-kotlinc:test --no-daemon
+        run: nix develop --command mvn --batch-mode -pl scip-kotlinc -am test
 
       - name: Regenerate snapshots
-        run: nix develop --command gradle :scip-snapshots:saveSnapshots --no-daemon
+        run: nix develop --command mvn --batch-mode -pl scip-snapshots -am -DskipTests -PsaveSnapshots verify
 
       - name: Check snapshot drift
         run: |
@@ -141,13 +142,13 @@ jobs:
 
       - run: |
           nix develop .#jdk${{ matrix.java }} --command \
-            gradle --no-daemon :scip-java:installDist publishToMavenLocal
+            mvn --batch-mode -DskipTests install
           SCIP_JAVA_VERSION="$(
-            sed -n 's/^version:=//p' scip-java/build/install/scip-java/VERSION
+            sed -n 's/^version:=//p' scip-java/target/install/scip-java/VERSION
           )"
           test -n "$SCIP_JAVA_VERSION"
           printf 'SCIP_JAVA_VERSION=%s\n' "$SCIP_JAVA_VERSION" >> "$GITHUB_ENV"
-          printf 'SCIP_JAVA_CLI=%s\n' "$PWD/scip-java/build/install/scip-java/bin/scip-java" >> "$GITHUB_ENV"
+          printf 'SCIP_JAVA_CLI=%s\n' "$PWD/scip-java/target/install/scip-java/bin/scip-java" >> "$GITHUB_ENV"
 
       - run: |
           nix develop "$GITHUB_WORKSPACE#jdk${{ matrix.java }}" --command \

.gitignore

@@ -13,6 +13,7 @@ build/
 .lib/
 dist/*
 target/
+.flattened-pom.xml
 lib_managed/
 src_managed/
 .bloop

BUILD.bazel

@@ -0,0 +1 @@
+# Root Bazel package for the rules_jvm_external Maven lock file.

CONTRIBUTING.md

@@ -14,17 +14,18 @@ nix develop .#jdk17      # JDK 17
 nix develop .#jdk21      # JDK 21
 ```
 
-This drops you into a shell with `gradle`, `maven`, `bazelisk`, `nodejs`,
+This drops you into a shell with `maven`, `gradle`, `bazelisk`, `nodejs`,
 `yarn`, `git`, `jq`, etc. all pinned to the versions used in CI.
 
 If you'd rather install tools manually, you'll need at least:
 
 - `java`: any version should work
 - `git`: any version should work
-- `gradle`: `brew install gradle`, or see
-  [general installation guide](https://gradle.org/install/).
 - `mvn`: `brew install maven`, or see
   [general installation guide](https://www.baeldung.com/install-maven-on-windows-linux-mac).
+- `gradle`: `brew install gradle`, or see
+  [general installation guide](https://gradle.org/install/). The project build
+  is Maven-based, but the CLI integration tests still exercise Gradle projects.
 
 ## Project structure
 
@@ -43,21 +44,22 @@ These are the main components of the project.
   interface.
 - `scip-java/src/test`: build-tool integration tests and fixtures for the
   `scip-java` command-line interface.
-- `settings.gradle.kts`: Gradle project layout.
-- `build.gradle.kts`: Gradle build definition.
-- `gradle/libs.versions.toml`: dependency and plugin versions.
+- `pom.xml`: Maven reactor, dependency versions, and shared plugin setup.
+- `*/pom.xml`: Maven module build definitions.
+- `build.gradle.kts`, `settings.gradle.kts`, `gradle/libs.versions.toml`: legacy
+  Gradle build files kept during the Maven migration experiment.
 
 ## Helpful commands
 
 | Command                                                 | Where    | Description                                                             |
 | ------------------------------------------------------- | -------- | ----------------------------------------------------------------------- |
-| `gradle test --no-daemon`                               | terminal | Run all Gradle tests.                                                    |
-| `gradle :scip-java:test --no-daemon`                    | terminal | Run CLI build-tool integration tests (Gradle, Maven, SCIP config).       |
-| `gradle :scip-kotlinc:test --no-daemon`                 | terminal | Run Kotlin compiler-plugin tests.                                        |
-| `gradle :scip-snapshots:test --no-daemon`               | terminal | Compare Java and Kotlin snapshot goldens.                                |
-| `gradle :scip-snapshots:saveSnapshots --no-daemon`      | terminal | Regenerate Java and Kotlin snapshot goldens.                             |
-| `gradle :scip-java:installDist --no-daemon`             | terminal | Build a local `scip-java` distribution under `scip-java/build/install/`. |
-| `gradle :scip-java:run --args='--cwd DIRECTORY'`        | terminal | Run `scip-java` against a given Gradle/Maven build.                      |
+| `mvn --batch-mode test`                                 | terminal | Run all Maven reactor tests.                                             |
+| `mvn --batch-mode -pl scip-java -am test`               | terminal | Run CLI build-tool integration tests (Gradle, Maven, SCIP config).       |
+| `mvn --batch-mode -pl scip-kotlinc -am test`            | terminal | Run Kotlin compiler-plugin tests.                                        |
+| `mvn --batch-mode -pl scip-snapshots -am test`          | terminal | Compare Java and Kotlin snapshot goldens.                                |
+| `mvn --batch-mode -pl scip-snapshots -am -DskipTests -PsaveSnapshots verify` | terminal | Regenerate Java and Kotlin snapshot goldens.                             |
+| `mvn --batch-mode -pl scip-java -am -DskipTests package` | terminal | Build a local `scip-java` distribution under `scip-java/target/install/`. |
+| `scip-java/target/install/scip-java/bin/scip-java --cwd DIRECTORY index` | terminal | Run `scip-java` against a given Gradle/Maven build after packaging.       |
 | `google-java-format --replace $(git ls-files '*.java')` | terminal | Format Java sources (from `nix develop`). Enforced by `nix flake check`. |
 | `ktfmt --kotlinlang-style $(git ls-files '*.kt')`       | terminal | Format Kotlin sources (from `nix develop`). Enforced by `nix flake check`. |
 
@@ -78,15 +80,15 @@ Next, follow
 [these instructions](https://github.com/HPI-Information-Systems/Metanome/wiki/Installing-the-google-styleguide-settings-in-intellij-and-eclipse)
 here to configure the Google Java formatter.
 
-Finally, run "File > Project From Existing Sources" to import the Gradle build
-into IntelliJ. Select the "Gradle" option if it asks you to choose a build
+Finally, run "File > Project From Existing Sources" to import the Maven build
+into IntelliJ. Select the "Maven" option if it asks you to choose a build
 model.
 
-It's best to run tests from Gradle, not from the IntelliJ UI.
+It's best to run tests from Maven, not from the IntelliJ UI.
 
 ## Tests are written in Java with JUnit 5
 
-The Java tests use [JUnit 5](https://junit.org/junit5/) through Gradle's JUnit
+The Java tests use [JUnit 5](https://junit.org/junit5/) through Maven Surefire's
 Platform support. The snapshot suite is a JUnit `@TestFactory` that emits one
 dynamic test per generated document, comparing it against the committed goldens
 under `scip-snapshots/expected`. Build-tool tests (`scip-java/src/test`) are

Dockerfile

@@ -17,7 +17,7 @@ RUN git config --global --add safe.directory *
 
 COPY . .
 
-RUN gradle --no-daemon :scip-java:installDist && mkdir -p /app/scip-java && cp -R scip-java/build/install/scip-java/. /app/scip-java/
+RUN mvn --batch-mode -pl scip-java -am -DskipTests package && mkdir -p /app/scip-java && cp -R scip-java/target/install/scip-java/. /app/scip-java/
 
 COPY ./bin/scip-java-docker-script.sh /usr/bin/scip-java
 

MODULE.bazel

@@ -13,6 +13,24 @@ maven.install(
         "org.scip-code:scip-java-bindings:0.8.0",
     ],
     known_contributing_modules = ["protobuf"],
-    repositories = ["https://repo1.maven.org/maven2"],
+    repositories = [
+        "https://repo1.maven.org/maven2",
+    ],
+    lock_file = "//:maven_install.json",
+)
+
+# Keep changing in-repo tool artifacts unpinned: `mvn install` populates m2Local
+# before Bazel runs, avoiding duplicate Bazel-side build rules for these jars.
+maven.install(
+    name = "local_maven",
+    artifacts = [
+        "com.sourcegraph:scip-aggregator:0.0.0-SNAPSHOT",
+        "com.sourcegraph:scip-javac:jar:all:0.0.0-SNAPSHOT",
+    ],
+    fail_on_missing_checksum = False,
+    repositories = [
+        "m2Local",
+        "https://repo1.maven.org/maven2",
+    ],
 )
-use_repo(maven, "maven")
+use_repo(maven, "maven", "local_maven")

examples/bazel-example/MODULE.bazel

@@ -24,4 +24,16 @@ maven.install(
     ],
     repositories = ["https://repo1.maven.org/maven2"],
 )
-use_repo(maven, "maven")
+
+# This source-checkout example consumes scip-java's SNAPSHOT tool jars from
+# m2Local. Run `mvn -DskipTests install` at the repository root first.
+maven.install(
+    name = "local_maven",
+    fail_on_missing_checksum = False,
+    known_contributing_modules = ["scip_java"],
+    repositories = [
+        "m2Local",
+        "https://repo1.maven.org/maven2",
+    ],
+)
+use_repo(maven, "maven", "local_maven")