Add "changes" output variable to support matrix job configuration

.github/workflows/pull-request-verification.yml

@@ -29,6 +29,9 @@ jobs:
     - name: filter-test
       if: steps.filter.outputs.any != 'true' || steps.filter.outputs.error == 'true'
       run: exit 1
+    - name: changes-test
+      if: contains(fromJSON(steps.filter.outputs.changes), 'error') || !contains(fromJSON(steps.filter.outputs.changes), 'any')
+      run: exit 1
 
   test-external:
     runs-on: ubuntu-latest

README.md

@@ -58,7 +58,7 @@ For more scenarios see [examples](#examples) section.
 ## Notes:
 - Paths expressions are evaluated using [picomatch](https://github.com/micromatch/picomatch) library.
   Documentation for path expression format can be found on project github page.
-- Micromatch [dot](https://github.com/micromatch/picomatch#options) option is set to true.
+- Picomatch [dot](https://github.com/micromatch/picomatch#options) option is set to true.
   Globbing will match also paths where file or folder name starts with a dot.
 - It's recommended to quote your path expressions with `'` or `"`. Otherwise you will get an error if it starts with `*`.
 - Local execution with [act](https://github.com/nektos/act) works only with alternative runner image. Default runner doesn't have `git` binary.
@@ -66,6 +66,7 @@ For more scenarios see [examples](#examples) section.
 
 
 # What's New
+- Configure matrix job to run for each folder with changes using `changes` output
 - Improved listing of matching files with `list-files: shell` and `list-files: escape` options
 - Support local changes
 - Fixed retrieval of all changes via Github API when there are 100+ changes
@@ -122,9 +123,9 @@ For more information see [CHANGELOG](https://github.com/actions/checkout/blob/ma
     # Enables listing of files matching the filter:
     #   'none'  - Disables listing of matching files (default).
     #   'json'  - Matching files paths are formatted as JSON array.
-    #   'shell' - Space delimited list usable as command line argument list in linux shell.
+    #   'shell' - Space delimited list usable as command line argument list in Linux shell.
     #             If needed it uses single or double quotes to wrap filename with unsafe characters.
-    #   'escape'- Space delimited list usable as command line argument list in linux shell.
+    #   'escape'- Space delimited list usable as command line argument list in Linux shell.
     #             Backslash escapes every potentially unsafe character.
     # Default: none
     list-files: ''
@@ -147,6 +148,7 @@ For more information see [CHANGELOG](https://github.com/actions/checkout/blob/ma
    - `'true'` - if **any** of changed files matches any of filter rules
    - `'false'` - if **none** of changed files matches any of filter rules
 - If enabled, for each filter it sets output variable with name `${FILTER_NAME}_files`. It will contain list of all files matching the filter.
+- `changes` - JSON array with names of all filters matching any of changed files.
 
 # Examples
 
@@ -230,6 +232,41 @@ jobs:
 ```
 </details>
 
+<details>
+<summary>Use change detection to configure matrix job</summary>
+
+```yaml
+jobs:
+  # JOB to run change detection
+  changes:
+    runs-on: ubuntu-latest
+    outputs:
+      # Expose matched filters as job 'packages' output variable
+      packages: ${{ steps.filter.outputs.changes }}
+    steps:
+    # For pull requests it's not necessary to checkout the code
+    - uses: dorny/paths-filter@v2
+      id: filter
+      with:
+        filters: |
+          package1: src/package1
+          package2: src/package2
+
+  # JOB to build and test each of modified packages
+  build:
+    needs: changes
+    strategy:
+      matrix:
+        # Parse JSON array containing names of all filters matching any of changed files
+        # e.g. ['package1', 'package2'] if both package folders contains changes
+        package: ${{ fromJson(needs.changes.outputs.packages) }}
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - ...
+```
+</details>
+
 ## Change detection workflows
 
 <details>
@@ -406,7 +443,7 @@ jobs:
     # Enable listing of files matching each filter.
     # Paths to files will be available in `${FILTER_NAME}_files` output variable.
     # Paths will be escaped and space-delimited.
-    # Output is usable as command line argument list in linux shell
+    # Output is usable as command line argument list in Linux shell
     list-files: shell
 
     # In this example changed files will be checked by linter.

action.yml

@@ -37,6 +37,9 @@ inputs:
       This option takes effect only when changes are detected using git against different base branch.
     required: false
     default: '10'
+outputs:
+  changes:
+    description: JSON array with names of all filters matching any of changed files
 runs:
   using: 'node12'
   main: 'dist/index.js'

dist/index.js

@@ -4791,10 +4791,12 @@ async function getChangedFilesFromApi(token, pullRequest) {
 }
 function exportResults(results, format) {
     core.info('Results:');
+    const changes = [];
     for (const [key, files] of Object.entries(results)) {
         const value = files.length > 0;
         core.startGroup(`Filter ${key} = ${value}`);
         if (files.length > 0) {
+            changes.push(key);
             core.info('Matching files:');
             for (const file of files) {
                 core.info(`${file.filename} [${file.status}]`);
@@ -4809,6 +4811,14 @@ function exportResults(results, format) {
             core.setOutput(`${key}_files`, filesValue);
         }
     }
+    if (results['changes'] === undefined) {
+        const changesJson = JSON.stringify(changes);
+        core.info(`Changes output set to ${changesJson}`);
+        core.setOutput('changes', changesJson);
+    }
+    else {
+        core.info('Cannot set changes output variable - name already used by filter output');
+    }
     core.endGroup();
 }
 function serializeExport(files, format) {

src/main.ts

@@ -175,10 +175,12 @@ async function getChangedFilesFromApi(
 
 function exportResults(results: FilterResults, format: ExportFormat): void {
   core.info('Results:')
+  const changes = []
   for (const [key, files] of Object.entries(results)) {
     const value = files.length > 0
     core.startGroup(`Filter ${key} = ${value}`)
     if (files.length > 0) {
+      changes.push(key)
       core.info('Matching files:')
       for (const file of files) {
         core.info(`${file.filename} [${file.status}]`)
@@ -193,6 +195,14 @@ function exportResults(results: FilterResults, format: ExportFormat): void {
       core.setOutput(`${key}_files`, filesValue)
     }
   }
+
+  if (results['changes'] === undefined) {
+    const changesJson = JSON.stringify(changes)
+    core.info(`Changes output set to ${changesJson}`)
+    core.setOutput('changes', changesJson)
+  } else {
+    core.info('Cannot set changes output variable - name already used by filter output')
+  }
   core.endGroup()
 }