Fix docs about component installation for system-provided (#615)

Closes #610

README.md

@@ -55,9 +55,9 @@ jobs:
 -   `skip_install`: (Optional) Skip the `gcloud` installation and use the
     [system-installed gcloud][github-runners] instead. This can dramatically
     improve workflow speeds at the expense of a slightly older gcloud version.
-    Setting this to `true` ignores any value for the `version` input. Even if
-    installation is skipped, this GitHub Action will still configure any
-    components or project metadata. The default value is `false`.
+    Setting this to `true` ignores any value for the `version` input. If you
+    skip installation, you will be unable to install components because the
+    system-install gcloud is locked. The default value is `false`.
 
 -   `version`: (Optional) A string representing the version or version
     constraint of the Cloud SDK (`gcloud`) to install (e.g. `"290.0.1"` or `">=

src/main.ts

@@ -51,14 +51,27 @@ export async function run(): Promise<void> {
 
   try {
     const skipInstall = parseBoolean(core.getInput('skip_install'));
+    let version = presence(core.getInput('version'));
+    const components = core.getInput('install_components');
+    const projectId = core.getInput('project_id');
+
     if (skipInstall) {
       core.info(`Skipping installation ("skip_install" was true)`);
+      if (version) {
+        core.warning(`Ignoring "version" because "skip_install" was true!`);
+      }
+
+      if (components) {
+        core.warning(
+          `Installing custom components with the system-provided gcloud may fail. ` +
+            `Set "skip_install" to false to install a managed version.`,
+        );
+      }
     } else {
       // Compute the version information. If the version was not specified,
       // accept any installed version. If the version was specified as "latest",
       // compute the latest version. Otherwise, accept the version/version
       // constraint as-is.
-      let version = presence(core.getInput('version'));
       if (!version) {
         core.debug(`version was unset, defaulting to any version`);
         version = '> 0.0.0';
@@ -80,7 +93,6 @@ export async function run(): Promise<void> {
     }
 
     // Install additional components
-    const components = core.getInput('install_components');
     if (components) {
       await installComponent(components.split(',').map((comp) => comp.trim()));
     }
@@ -97,7 +109,6 @@ export async function run(): Promise<void> {
     }
 
     // Set the project ID, if given.
-    const projectId = core.getInput('project_id');
     if (projectId) {
       await setProject(projectId);
       core.info('Successfully set default project');