feat: Support a Bazel Path (#29)

- Allow users to pass in a path to the Bazel path executable. Useful for
custom installations of Bazel.
- Only install Bazel to the PATH if the expected bazel-path is `bazel`,
but no bazel exists. If a user provides a custom bazel-path, we assume
the executable exists. Similarly, if bazel already exists, no need to
install.

.github/workflows/compute_impacted_tests.yaml

@@ -25,6 +25,7 @@ jobs:
           VERBOSE: 1
           WORKSPACE_PATH: ./tests/simple_bazel_workspace
           BAZEL_STARTUP_OPTIONS: --host_jvm_args=-Xmx12G,--block_for_lock,--client_debug
+          BAZEL_PATH: bazel
 
       - name: Validate Impacted Targets Computation
         shell: bash

action.yaml

@@ -25,18 +25,14 @@ inputs:
       https://bazel.build/reference/command-line-reference#startup-options for a complete list. If
       unspecified, no startup options are specified.
     required: false
+  bazel-path:
+    description: A path to the Bazel executable. Defaults to PATH.
+    required: false
+    default: bazel
 
 runs:
   using: composite
   steps:
-    - name: Setup Bazel
-      # trunk-ignore(semgrep): Trust third-party `bazelbuild` GH Action
-      uses: bazelbuild/setup-bazelisk@v2
-
-    - name: Setup jq
-      # trunk-ignore(semgrep): Trust third-party action to install JQ. Source code: https://github.com/dcarbone/install-jq-action/
-      uses: dcarbone/install-jq-action@v1.0.1
-
     - name: Prerequisites
       id: prerequisites
       run: ${GITHUB_ACTION_PATH}/src/scripts/prerequisites.sh
@@ -45,6 +41,16 @@ runs:
         DEFAULT_BRANCH: ${{ github.event.repository.default_branch }}
         TARGET_BRANCH: ${{ inputs.target-branch }}
         WORKSPACE_PATH: ${{ inputs.bazel-workspace-path }}
+        BAZEL_PATH: ${{ inputs.bazel-path }}
+
+    - name: Install Bazel in PATH
+      if: ${{ steps.prerequisites.outputs.requires_default_bazel_installation == 'true' }}
+      # trunk-ignore(semgrep): Trust third-party `bazelbuild` GH Action
+      uses: bazelbuild/setup-bazelisk@v2
+
+    - name: Setup jq
+      # trunk-ignore(semgrep): Trust third-party action to install JQ. Source code: https://github.com/dcarbone/install-jq-action/
+      uses: dcarbone/install-jq-action@v1.0.1
 
     - name: Compute Impacted Targets
       id: compute-impacted-targets
@@ -55,6 +61,7 @@ runs:
         PR_BRANCH: ${{ github.head_ref }}
         VERBOSE: ${{ inputs.verbose }}
         WORKSPACE_PATH: ${{ steps.prerequisites.outputs.workspace_path }}
+        BAZEL_PATH: ${{ inputs.bazel-path }}
         BAZEL_STARTUP_OPTIONS: ${{ inputs.bazel-startup-options }}
 
     - name: Upload Impacted Targets

src/scripts/compute_impacted_targets.sh

@@ -33,7 +33,7 @@ logIfVerbose "Bazel startup options" "${bazel_startup_options}"
 
 _bazel() {
 	# trunk-ignore(shellcheck)
-	bazel ${bazel_startup_options} "$@"
+	${BAZEL_PATH} ${bazel_startup_options} "$@"
 }
 
 # trunk-ignore(shellcheck)
@@ -91,7 +91,7 @@ fi
 # Install the bazel-diff JAR. Avoid cloning the repo, as there will be conflicting WORKSPACES.
 curl --retry 5 -Lo bazel-diff.jar https://github.com/Tinder/bazel-diff/releases/latest/download/bazel-diff_deploy.jar
 _java -jar bazel-diff.jar -V
-bazel version # Does not require running with startup options.
+_bazel version # Does not require running with startup options.
 
 # Output Files
 merge_instance_branch_out=./${merge_instance_branch_head_sha}
@@ -100,11 +100,11 @@ impacted_targets_out=./impacted_targets_${pr_branch_head_sha}
 
 # Generate Hashes for the Merge Instance Branch
 git switch "${MERGE_INSTANCE_BRANCH}"
-bazelDiff generate-hashes --workspacePath="${WORKSPACE_PATH}" "-so=${bazel_startup_options}" "${merge_instance_branch_out}"
+bazelDiff generate-hashes --bazelPath="${BAZEL_PATH}" --workspacePath="${WORKSPACE_PATH}" "-so=${bazel_startup_options}" "${merge_instance_branch_out}"
 
 # Generate Hashes for the Merge Instance Branch + PR Branch
 git -c "user.name=Trunk Actions" -c "user.email=actions@trunk.io" merge --squash "${PR_BRANCH}"
-bazelDiff generate-hashes --workspacePath="${WORKSPACE_PATH}" "-so=${bazel_startup_options}" "${merge_instance_with_pr_branch_out}"
+bazelDiff generate-hashes --bazelPath="${BAZEL_PATH}" --workspacePath="${WORKSPACE_PATH}" "-so=${bazel_startup_options}" "${merge_instance_with_pr_branch_out}"
 
 # Compute impacted targets
 bazelDiff get-impacted-targets --startingHashes="${merge_instance_branch_out}" --finalHashes="${merge_instance_with_pr_branch_out}" --output="${impacted_targets_out}"

src/scripts/prerequisites.sh

@@ -18,6 +18,15 @@ if [[ -z ${workspace_path} ]]; then
 	workspace_path=$(pwd)
 fi
 
+requires_default_bazel_installation="false"
+if [[ ${BAZEL_PATH} == "bazel" ]]; then
+	if ! command -v bazel; then
+		requires_default_bazel_installation="true"
+	fi
+fi
+
 # Outputs
+# trunk-ignore(shellcheck/SC2129)
 echo "merge_instance_branch=${merge_instance_branch}" >>"${GITHUB_OUTPUT}"
 echo "workspace_path=${workspace_path}" >>"${GITHUB_OUTPUT}"
+echo "requires_default_bazel_installation=${requires_default_bazel_installation}" >>"${GITHUB_OUTPUT}"