Update Documentation for Lockfile (#1454)

* update documentation for lockfile

* Update adavance usage in README.md

* Documentation update

* Update lockfile documenation

* fix coplilot suggestion

README.md

@@ -148,7 +148,7 @@ Since it will not be cached always, there is possibility of hitting rate limit w
 
 ### Checking in lockfiles
 
-It's **always** recommended to commit the lockfile of your package manager for security and performance reasons. For more information consult the "Working with lockfiles" section of the [Advanced usage](docs/advanced-usage.md#working-with-lockfiles) guide.
+It's **strongly recommended** to commit the lockfile of your package manager for security and performance reasons. For more information consult the "Working with lockfiles" section of the [Advanced usage](docs/advanced-usage.md#working-with-lockfiles) guide.
 
 ## Caching global packages data
 
@@ -249,6 +249,7 @@ If the runner is not able to access github.com, any Nodejs versions requested du
  - [Publishing to npmjs and GPR with npm](docs/advanced-usage.md#publish-to-npmjs-and-gpr-with-npm)
  - [Publishing to npmjs and GPR with yarn](docs/advanced-usage.md#publish-to-npmjs-and-gpr-with-yarn)
  - [Using private packages](docs/advanced-usage.md#use-private-packages)
+ - [Using private mirror](docs/advanced-usage.md#use-private-mirror)
 
 ## Recommended permissions
 

docs/advanced-usage.md

@@ -1,6 +1,6 @@
 ## Working with lockfiles
 
-All supported package managers recommend that you **always** commit the lockfile, although implementations vary doing so generally provides the following benefits:
+Most supported package managers recommend that you **always** commit the lockfile, although implementations vary doing so generally provides the following benefits:
 
 - Enables faster installation for CI and production environments, due to being able to skip package resolution.
 - Describes a single representation of a dependency tree such that teammates, deployments, and continuous integration are guaranteed to install exactly the same dependencies.
@@ -35,6 +35,25 @@ Ensure that `pnpm-lock.yaml` is always committed, when on CI pass `--frozen-lock
 - [Working with Git - Lockfiles](https://pnpm.io/git#lockfiles)
 - [Documentation of `--frozen-lockfile` option](https://pnpm.io/cli/install#--frozen-lockfile)
 
+### Running without a lockfile
+
+If you choose not to use a lockfile, you must ensure that **caching is disabled**. The `cache` feature relies on the lockfile to generate a unique key for the cache entry.
+
+To run without a lockfile:
+1. Do not set the `cache` input.
+2. If your `package.json` contains a `packageManager` field set to npm (or devEngines.packageManager), automatic caching is enabled by default. Override this by setting `package-manager-cache: false`.
+
+```yaml
+steps:
+- uses: actions/checkout@v6
+- uses: actions/setup-node@v6
+  with:
+    node-version: '24'
+    package-manager-cache: false # Explicitly disable caching if you don't have a lockfile
+- run: npm install
+- run: npm test
+```
+
 ## Check latest version
 
 The `check-latest` flag defaults to `false`. When set to `false`, the action will first check the local cache for a semver match. If unable to find a specific version in the cache, the action will attempt to download a version of Node.js. It will pull LTS versions from [node-versions releases](https://github.com/actions/node-versions/releases) and on miss or failure will fall back to the previous behavior of downloading directly from [node dist](https://nodejs.org/dist/). Use the default or set `check-latest` to `false` if you prefer stability and if you want to ensure a specific version of Node.js is always used.