Add minor documentation for Bazel, fixes #445

Author: olafurpg

README.md

@@ -7,4 +7,3 @@
 | Manual configuration | https://sourcegraph.github.io/scip-java/docs/manual-configuration.html |
 | Contributing         | https://sourcegraph.github.io/scip-java/docs/contributing.html         |
 | Design               | https://sourcegraph.github.io/scip-java/docs/design.html               |
-

docs/getting-started.md

@@ -241,7 +241,7 @@ free to subscribe to the tracking issues to receive updates on your build tool.
 | Gradle     | ✅   | ✅    | ✅     |                                                                                  |
 | sbt        | ✅   | ✅    | n/a    |                                                                                  |
 | Ant        | ❌   | ❌    | ❌     | [sourcegraph/scip-java#305](https://github.com/sourcegraph/scip-java/issues/305) |
-| Bazel      | ❌   | ❌    | ❌     | [sourcegraph/scip-java#88](https://github.com/sourcegraph/scip-java/issues/88)   |
+| Bazel      | ✅   | ✅    | ❌     |                                                                                  |
 | Buck       | ❌   | ❌    | ❌     | [sourcegraph/scip-java#99](https://github.com/sourcegraph/scip-java/issues/99)   |
 | Mill       | ❌   | ❌    | ❌     | [sourcegraph/scip-java#306](https://github.com/sourcegraph/scip-java/issues/306) |
 
@@ -299,3 +299,23 @@ projects, with the following caveats:
 | ------------- | --------- | ----------------------- |
 | sbt <v0.13.17 | ❌        | Upgrade to sbt v0.13.17 |
 
+### Bazel
+
+Bazel is supported by scip-java but it requires custom configuration to work
+correctly. Note that the `scip-java index` command does not automatically index
+Bazel builds.
+
+The Bazel integration for scip-java is specifically designed to be compatible
+with the Bazel build cache to enable incremental indexing. To achieve this,
+scip-java must be configured in `WORKSPACE` and `BUILD` files. The scip-java
+repository contains an example for how to configure everything.
+
+- [WORKSPACE](https://github.com/sourcegraph/scip-java/blob/main/examples/bazel-example/WORKSPACE):
+  adds the required dependencies to be able to run scip-java itself.
+- [BUILD](https://github.com/sourcegraph/scip-java/blob/main/examples/bazel-example/src/main/java/example/BUILD):
+  configured `java_library` and `java_binary` targets to be indexed with
+  scip-java.
+
+Don't hesitate to open an issue in the
+[scip-java repository](https://github.com/sourcegraph/scip-java) if you have any
+questions about using scip-java with Bazel builds.

scip-java/src/main/scala/com/sourcegraph/scip_java/buildtools/BazelBuildTool.scala

@@ -0,0 +1,25 @@
+package com.sourcegraph.scip_java.buildtools
+
+import java.nio.file.Files
+
+import com.sourcegraph.scip_java.commands.IndexCommand
+
+class BazelBuildTool(index: IndexCommand) extends BuildTool("Bazel", index) {
+
+  override def usedInCurrentDirectory(): Boolean = {
+    Files.isRegularFile(index.workingDirectory.resolve("WORKSPACE"))
+  }
+
+  override def generateScip(): Int = {
+    index
+      .app
+      .reporter
+      .error(
+        "The `scip-java index` command does not work with Bazel builds because Bazel " +
+          "requires custom configuration to be added to WORKSPACE and BUILD files. " +
+          "The scip-java repository contains an example WORKSPACE file to demonstrate " +
+          "how to use scip-java with Bazel https://github.com/sourcegraph/scip-java/blob/main/examples/bazel-example/WORKSPACE"
+      )
+    1
+  }
+}

scip-java/src/main/scala/com/sourcegraph/scip_java/buildtools/BuildTool.scala

@@ -20,6 +20,7 @@ abstract class BuildTool(val name: String, index: IndexCommand) {
 object BuildTool {
   def all(index: IndexCommand): List[BuildTool] =
     List(
+      new BazelBuildTool(index),
       new GradleBuildTool(index),
       new MavenBuildTool(index),
       new ScipBuildTool(index),