Output the stat data

README.md

@@ -70,6 +70,7 @@ For more scenarios see [examples](#examples) section.
 
 ## What's New
 
+- Add `stat` parameter that enables output of the file changes statistics per filter.
 - Add `ref` input parameter
 - Add `list-files: csv` format
 - Configure matrix job to run for each folder with changes using `changes` output
@@ -160,6 +161,7 @@ For more information, see [CHANGELOG](https://github.com/dorny/paths-filter/blob
 - For each filter, it sets an output variable with the name `${FILTER_NAME}_count` to the count of matching files.
 - If enabled, for each filter it sets an output variable with the name `${FILTER_NAME}_files`. It will contain a list of all files matching the filter.
 - `changes` - JSON array with names of all filters matching any of the changed files.
+- If `stat` input is set to an output format, the output variable `stat` contains JSON or CSV value with the change statistics for each filter.
 
 ## Examples
 
@@ -504,6 +506,33 @@ jobs:
 
 </details>
 
+<details>
+  <summary>Passing number of added lines from a filter to another action</summary>
+
+```yaml
+- uses: dorny/paths-filter@v2
+  id: filter
+  with:
+    # Enable listing of diff stat matching each filter.
+    # Paths to files will be available in `stat` output variable.
+    # Stat will be formatted as JSON object
+    stat: json
+
+    # In this example all changed files are passed to the following action to do
+    # some custom processing.
+    filters: |
+      changed:
+        - '**'
+- name: Lint Markdown
+  uses: johndoe/some-action@v1
+  # Run action only if the change is large enough.
+  if: ${{fromJson(steps.filter.outputs.stat).changed.additionCount > 1000}}
+  with:
+    files: ${{ steps.filter.outputs.changed_files }}
+```
+
+</details>
+
 ## See also
 
 - [test-reporter](https://github.com/dorny/test-reporter) - Displays test results from popular testing frameworks directly in GitHub

__tests__/filter.test.ts

@@ -150,7 +150,7 @@ describe('matching specific change status', () => {
       - added: "**/*"
     `
     let filter = new Filter(yaml)
-    const files = [{status: ChangeStatus.Added, filename: 'file.js'}]
+    const files = [{status: ChangeStatus.Added, filename: 'file.js', additions: 1, deletions: 0}]
     const match = filter.match(files)
     expect(match.add).toEqual(files)
   })
@@ -161,7 +161,7 @@ describe('matching specific change status', () => {
       - added|modified: "**/*"
     `
     let filter = new Filter(yaml)
-    const files = [{status: ChangeStatus.Modified, filename: 'file.js'}]
+    const files = [{status: ChangeStatus.Modified, filename: 'file.js', additions: 1, deletions: 1}]
     const match = filter.match(files)
     expect(match.addOrModify).toEqual(files)
   })
@@ -183,6 +183,6 @@ describe('matching specific change status', () => {
 
 function modified(paths: string[]): File[] {
   return paths.map(filename => {
-    return {filename, status: ChangeStatus.Modified}
+    return {filename, status: ChangeStatus.Modified, additions: 1, deletions: 1}
   })
 }

__tests__/git.test.ts

@@ -2,8 +2,8 @@ import * as git from '../src/git'
 import {ChangeStatus} from '../src/file'
 
 describe('parsing output of the git diff command', () => {
-  test('parseGitDiffOutput returns files with correct change status', async () => {
-    const files = git.parseGitDiffOutput(
+  test('parseGitDiffNameStatusOutput returns files with correct change status', async () => {
+    const files = git.parseGitDiffNameStatusOutput(
       'A\u0000LICENSE\u0000' + 'M\u0000src/index.ts\u0000' + 'D\u0000src/main.ts\u0000'
     )
     expect(files.length).toBe(3)
@@ -14,6 +14,19 @@ describe('parsing output of the git diff command', () => {
     expect(files[2].filename).toBe('src/main.ts')
     expect(files[2].status).toBe(ChangeStatus.Deleted)
   })
+
+  test('parseGitDiffNumstatOutput returns files with correct change status', async () => {
+    const files = git.parseGitDiffNumstatOutput(
+      '4\t2\tLICENSE\u0000' + '5\t0\tsrc/index.ts\u0000'
+    )
+    expect(files.length).toBe(2)
+    expect(files[0].filename).toBe('LICENSE')
+    expect(files[0].additions).toBe(4)
+    expect(files[0].deletions).toBe(2)
+    expect(files[1].filename).toBe('src/index.ts')
+    expect(files[1].additions).toBe(5)
+    expect(files[1].deletions).toBe(0)
+  })
 })
 
 describe('git utility function tests (those not invoking git)', () => {

action.yml

@@ -36,6 +36,16 @@ inputs:
                   Backslash escapes every potentially unsafe character.
     required: true
     default: none
+  stat:
+    description: |
+      Enables listing of that enables output of the file change statistics per filter, similar to `git diff --shortstat`.
+      If some changes do not match any filter, the output includes an additional entry with the filter name 'other'.
+        'none'  - Disables listing of stats (default).
+        'csv'   - Coma separated list that has name of filter, count of additions, count of deletions, count of changed files.
+                  If needed it uses double quotes to wrap name of filter with unsafe characters. For example, `"some filter",12,7,2`.
+        'json'  - Serialized as JSON object where the filter names are keys. For example, `{"some filter": {"additionCount": 12, "deletionCount": 7, "fileCount": 2}}`
+    required: false
+    default: none
   initial-fetch-depth:
     description: |
       How many commits are initially fetched from base branch.