feat(internal/librarian/nodejs): use cache and bin directories for nodejs install

[suztomo]

Update NodeJS tool installation to use $LIBRARIAN_BIN/nodejs_tools for installed executables (aligning with go_tools and java_tools) and LIBRARIAN_CACHE for downloaded google-cloud-node repository and pnpm cache/store.

Fixes #6678

• Installs Node.js tools in $LIBRARIAN_BIN/nodejs_tools/bin (with PNPM_HOME=$LIBRARIAN_BIN/nodejs_tools and PNPM_CONFIG_GLOBAL_BIN_DIR=$LIBRARIAN_BIN/nodejs_tools/bin).
• Prepends $LIBRARIAN_BIN/nodejs_tools/bin to PATH during tool installation and generation to prevent pnpm warnings/errors about global bin directory not in PATH.
• Declares sentinel errors (errMissingExecutable, errMissingPackageURL, errCannotExtractRepo) evaluated with errors.Is.
• Table-driven tests in internal/librarian/nodejs/install_test.go use a pnpm shell script stub. The stub handles pnpm add -g for non-build tool installations and asserts that required transient environment variables (PNPM_HOME, PNPM_CONFIG_GLOBAL_BIN_DIR, PNPM_CONFIG_GLOBAL_DIR, PNPM_CONFIG_STORE_DIR, and PNPM_CONFIG_DANGEROUSLY_ALLOW_ALL_BUILDS) are present during execution.

I ran `librarian install` and the executables are installed in the cache folder.

suztomo@suztomo:~/librarian-2026/google-cloud-node$ rm $(which pbjs)
suztomo@suztomo:~/librarian-2026/google-cloud-node$ which gapic-node-processing
/usr/local/google/home/suztomo/.nvm/versions/node/v22.22.3/bin/gapic-node-processing
suztomo@suztomo:~/librarian-2026/google-cloud-node$ rm $(which gapic-node-processing)
suztomo@suztomo:~/librarian-2026/google-cloud-node$ which gapic-generator-java
suztomo@suztomo:~/librarian-2026/google-cloud-node$ which gapic-generator-typescript
/usr/local/google/home/suztomo/.nvm/versions/node/v22.22.3/bin/gapic-generator-typescript
suztomo@suztomo:~/librarian-2026/google-cloud-node$ rm $(which gapic-generator-typescript)
suztomo@suztomo:~/librarian-2026/google-cloud-node$ /tmp/librarian install
Already up to date
...

Done in 1s using pnpm v11.10.0
suztomo@suztomo:~/librarian-2026/google-cloud-node$ which gapic-generator-typescript
suztomo@suztomo:~/librarian-2026/google-cloud-node$ /tmp/librarian debug env
LIBRARIAN_CACHE=/usr/local/google/home/suztomo/.cache/librarian
LIBRARIAN_BIN=/usr/local/google/home/suztomo/.cache/librarian/bin

Language-specific tool installation directories:
  golang: /usr/local/google/home/suztomo/.cache/librarian/bin/go_tools
  java: /usr/local/google/home/suztomo/.cache/librarian/bin/java_tools
  nodejs: /usr/local/google/home/suztomo/.cache/librarian/bin/nodejs_tools
suztomo@suztomo:~/librarian-2026/google-cloud-node$ export PATH=$PATH:/usr/local/google/home/suztomo/.cache/librarian/bin/nodejs_tools/bin
suztomo@suztomo:~/librarian-2026/google-cloud-node$ which gapic-generator-typescript
/usr/local/google/home/suztomo/.cache/librarian/bin/nodejs_tools/bin/gapic-generator-typescript

I ran generate without setting the PATH. Librarian used the bin directory.

suztomo@suztomo:~/librarian-2026/google-cloud-node$ which gapic-node-processing
suztomo@suztomo:~/librarian-2026/google-cloud-node$ /tmp/librarian generate google-cloud-agentregistry
suztomo@suztomo:~/librarian-2026/google-cloud-node$ git diff |head -30
diff --git a/packages/google-cloud-agentregistry/protos/protos.js b/packages/google-cloud-agentregistry/protos/protos.js
index e8aaa3ea7c..6154bd8bc0 100644
--- a/packages/google-cloud-agentregistry/protos/protos.js
+++ b/packages/google-cloud-agentregistry/protos/protos.js
@@ -28,7 +28,7 @@
     var $Reader = $protobuf.Reader, $Writer = $protobuf.Writer, $util = $protobuf.util;
     
     // Exported root namespace
-    var $root = $protobuf.roots._google_cloud_agentregistry_protos || ($protobuf.roots._google_cloud_agentregistry_protos = {});
+    var $root = $protobuf.roots["_google_cloud_agentregistry_protos"] || ($protobuf.roots["_google_cloud_agentregistry_protos"] = {});
     
     $root.google = (function() {
     
@@ -230,9:13 @@
                          * @param {$protobuf.Writer} [writer] Writer to encode to
                          * @returns {$protobuf.Writer} Writer
                          */
-                        Agent.encode = function encode(message, writer) {
+                        Agent.encode = function encode(message, writer, q) {
                             if (!writer)
                                 writer = $Writer.create();
+                            if (q === undefined)
+                                q = 0;
+                            if (q > $util.recursionLimit)
+                                throw Error("max depth exceeded");
                             if (message.name != null && Object.hasOwnProperty.call(message, "name"))
                                 writer.uint32(/* id 1, wireType 2 =*/10).string(message.name);
                             if (message.agentId != null && Object.hasOwnProperty.call(message, "agentId"))
@@ -247,23 +251,23 @@
                                 writer.uint32(/* id 7, wireType 2 =*/58).string(message.version);

[gemini-code-assist]

Code Review

This pull request integrates Node.js tool installation paths into the librarian debug environment and updates Node.js command execution to run with the correct tools environment. It also refactors getPNPMEnv to configure pnpm paths using the librarian cache and bin directories instead of querying Node dynamically. Feedback was provided regarding a hardcoded path separator (:) when updating the PATH environment variable, which could cause issues on Windows; using os.PathListSeparator is recommended for cross-platform compatibility.

[suztomo]

Coverage...

ok  	github.com/googleapis/librarian/internal/librarian/nodejs	1.169s	coverage: 70.8% of statements
Coverage: 70.8% (target: 73%)
FAIL: coverage 70.8% is below target 73%

[suztomo]

The rest coverage is good now.

[suztomo]

Updated to use nodejs_tools:

suztomo@suztomo:~/librarian-2026/librarian$ ls /usr/local/google/home/suztomo/.cache/librarian/bin/nodejs_tools/bin
compileProtos  gapic-generator-typescript  gapic-node-processing  listProtos  minifyProtoJson  pbjs  pbts  prepublishProtos  protoc-gen-typescript_gapic

It's itchy that the 'bin' folder contains a folder that contains 'bin'. But I don't address that in this pull request.

[JoeWang1127]

It's itchy that the 'bin' folder contains a folder that contains 'bin'. But I don't address that in this pull request.

Could you create an issue for this, I can come up with another directory name.

[suztomo]

Filed #6695.