Merge pull request actions#299 from actions/malob/adr-caching-monorepos

ADR for support caching for mono repos and repositories with complex structure

Author: MaksimZhukov

docs/adrs/0000-caching-dependencies.md

@@ -1,7 +1,7 @@
 # 0. Caching dependencies
 Date: 2021-05-21
 
-Status: Proposed
+Status: Accepted
 
 # Context
 `actions/setup-node` is the 2nd most popular action in GitHub Actions. A lot of customers use it in conjunction with [actions/cache](https://github.com/actions/cache) to speed up dependencies installation.  

docs/adrs/0001-support-caching-deps-for-monorepos.md

@@ -0,0 +1,48 @@
+# 0. Support caching dependencies for mono repos
+Date: 2021-07-13
+
+Status: Proposed
+
+## Context
+Currently, `actions/setup-node` supports caching dependencies for Npm and Yarn package managers.  
+For the first iteration, we have decided to not support cases where `package-lock.json` / `yarn.lock` are located outside of repository root.  
+Current implementation searches the following file patterns in the repository root: `package-lock.json`, `yarn.lock` (in order of resolving priorities)
+
+Obviously, it made build-in caching unusable for mono-repos and repos with complex structure.  
+We would like to revisit this decision and add customization for dependencies lock file location.
+
+## Proposal
+We have the following options:
+1. Allow to specify  directory where `package-lock.json` or `yarn.lock` are located
+2. Allow to specify path to the dependencies lock file (including directory path and filename)
+
+The second option looks more generic because it allows to:
+- specify multiple dependencies files using file patterns like `**/package-lock.json` ([one of recommended approaches in actions/cache](https://github.com/actions/cache/blob/main/examples.md#macos-and-ubuntu))
+- specify custom dependencies files like `src/npm-shrinkwrap.json`
+- change default resolving priority if both `yarn.lock` and `package-lock.json` exist in repository
+
+## Decision
+
+Add `cache-dependency-path` input that will accept path (relative to repository root) to dependencies lock file.  
+If provided path contains wildcards, the action will search all maching files and calculate common hash like `${{ hashFiles('**/package-lock.json') }}` YAML construction does.  
+The hash of provided matched files will be used as a part of cache key.
+
+Yaml examples:
+```yml
+steps:
+- uses: actions/checkout@v2
+- uses: actions/setup-node@v2
+  with:
+    node-version: 14
+    cache: npm
+    cache-dependency-path: 'sub-project/package-lock.json'
+```
+```yml
+steps:
+- uses: actions/checkout@v2
+- uses: actions/setup-node@v2
+  with:
+    node-version: 14
+    cache: yarn
+    cache-dependency-path: 'sub-project/**/yarn.lock'
+```