Add caching for the Mill build tool

.github/workflows/e2e-cache.yml

@@ -207,3 +207,93 @@ jobs:
             exit 1
           fi
           ls ~/.cache/coursier
+  mill-save:
+    runs-on: ${{ matrix.os }}
+    defaults:
+      run:
+        shell: bash
+        working-directory: __tests__/cache/mill
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [macos-13, windows-latest, ubuntu-22.04]
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Run setup-java with the cache for mill
+        uses: ./
+        id: setup-java
+        with:
+          distribution: 'adopt'
+          java-version: '11'
+          cache: mill
+      - name: Create files to cache
+        run: ./mill --disable-ticker _.compile
+
+      - name: Check files to cache on macos-latest
+        if: matrix.os == 'macos-13'
+        run: |
+          if [ ! -d ~/.cache/mill/download ]; then
+            echo "::error::The ~/.cache/mill/download directory does not exist unexpectedly"
+            exit 1
+          fi
+      - name: Check files to cache on windows-latest
+        if: matrix.os == 'windows-latest'
+        run: |
+          if [ ! -d %USERPROFILE%/.cache/mill/download ]; then
+            echo "::error::The %USERPROFILE%/.cache/mill/download directory does not exist unexpectedly"
+            exit 1
+          fi
+      - name: Check files to cache on ubuntu-latest
+        if: matrix.os == 'ubuntu-latest'
+        run: |
+          if [ ! -d ~/.cache/mill/download ]; then
+            echo "::error::The ~/.cache/mill/download directory does not exist unexpectedly"
+            exit 1
+          fi
+  mill-restore:
+    runs-on: ${{ matrix.os }}
+    defaults:
+      run:
+        shell: bash
+        working-directory: __tests__/cache/mill
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [macos-13, windows-latest, ubuntu-22.04]
+    needs: mill-save
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Run setup-java with the cache for mill
+        uses: ./
+        id: setup-java
+        with:
+          distribution: 'adopt'
+          java-version: '11'
+          cache: mill
+
+      - name: Confirm that ~/.cache/mill/download directory has been made
+        if: matrix.os == 'macos-13'
+        run: |
+          if [ ! -d ~/.cache/mill/download ]; then
+            echo "::error::The ~/.cache/mill/download directory does not exist unexpectedly"
+            exit 1
+          fi
+          ls ~/.cache/mill/download
+      - name: Confirm that %USERPROFILE%/.cache/mill/download directory has been made
+        if: matrix.os == 'windows-latest'
+        run: |
+          if [ ! -d %USERPROFILE%/.cache/mill/download ]; then
+            echo "::error::The %USERPROFILE%/.cache/mill/download directory does not exist unexpectedly"
+            exit 1
+          fi
+          ls %USERPROFILE%/.cache/mill/download
+      - name: Confirm that ~/.cache/mill/download directory has been made
+        if: matrix.os == 'ubuntu-latest'
+        run: |
+          if [ ! -d ~/.cache/mill/download ]; then
+            echo "::error::The ~/.cache/mill/download directory does not exist unexpectedly"
+            exit 1
+          fi
+          ls ~/.cache/mill/download

.gitignore

@@ -1,3 +1,6 @@
+# Ignore Scala IDE files
+.metals/
+
 # Ignore node_modules, ncc is used to compile nodejs modules into a single file
 node_modules/
 __tests__/runner/*

README.md

@@ -14,6 +14,7 @@ The `setup-java` action provides the following functionality for GitHub Actions
 - Caching dependencies managed by Apache Maven.
 - Caching dependencies managed by Gradle.
 - Caching dependencies managed by sbt.
+- Caching dependencies managed by Mill.
 - [Maven Toolchains declaration](https://maven.apache.org/guides/mini/guide-using-toolchains.html) for specified JDK versions.
 
 This action allows you to work with Java and Scala projects.
@@ -39,7 +40,7 @@ This action allows you to work with Java and Scala projects.
 
   - `check-latest`: Setting this option makes the action to check for the latest available version for the version spec.
 
-  - `cache`: Quick [setup caching](#caching-packages-dependencies) for the dependencies managed through one of the predefined package managers. It can be one of "maven", "gradle" or "sbt".
+  - `cache`: Quick [setup caching](#caching-packages-dependencies) for the dependencies managed through one of the predefined package managers. It can be one of "maven", "gradle", "sbt", or "mill".
 
   - `cache-dependency-path`: The path to a dependency file: pom.xml, build.gradle, build.sbt, etc. This option can be used with the `cache` option. If this option is omitted, the action searches for the dependency file in the entire repository. This option supports wildcards and a list of file names for caching multiple dependencies.
 
@@ -121,11 +122,12 @@ Currently, the following distributions are supported:
 **NOTE:** To comply with the GraalVM Free Terms and Conditions (GFTC) license, it is recommended to use GraalVM JDK 17 version 17.0.12, as this is the only version of GraalVM JDK 17 available under the GFTC license. Additionally, it is encouraged to consider upgrading to GraalVM JDK 21, which offers the latest features and improvements.
 
 ### Caching packages dependencies
-The action has a built-in functionality for caching and restoring dependencies. It uses [toolkit/cache](https://github.com/actions/toolkit/tree/main/packages/cache) under hood for caching dependencies but requires less configuration settings. Supported package managers are gradle, maven and sbt. The format of the used cache key is `setup-java-${{ platform }}-${{ packageManager }}-${{ fileHash }}`, where the hash is based on the following files:
+The action has a built-in functionality for caching and restoring dependencies. It uses [toolkit/cache](https://github.com/actions/toolkit/tree/main/packages/cache) under hood for caching dependencies but requires less configuration settings. Supported package managers are Gradle, Maven, sbt, and Mill. The format of the used cache key is `setup-java-${{ platform }}-${{ packageManager }}-${{ fileHash }}`, where the hash is based on the following files:
 
-- gradle: `**/*.gradle*`, `**/gradle-wrapper.properties`, `buildSrc/**/Versions.kt`, `buildSrc/**/Dependencies.kt`, `gradle/*.versions.toml`, and `**/versions.properties`
-- maven: `**/pom.xml`
+- Gradle: `**/*.gradle*`, `**/gradle-wrapper.properties`, `buildSrc/**/Versions.kt`, `buildSrc/**/Dependencies.kt`, `gradle/*.versions.toml`, and `**/versions.properties`
+- Maven: `**/pom.xml`
 - sbt: all sbt build definition files `**/*.sbt`, `**/project/build.properties`, `**/project/**.scala`, `**/project/**.sbt`
+- Mill: `**/build.sc`, `**/*.sc`, `**/mill`, `**/.mill-version`, and `**/.config/mill-version`
 
 When the option `cache-dependency-path` is specified, the hash is based on the matching file. This option supports wildcards and a list of file names, and is especially useful for monorepos.
 
@@ -133,7 +135,7 @@ The workflow output `cache-hit` is set to indicate if an exact match was found f
 
 The cache input is optional, and caching is turned off by default.
 
-#### Caching gradle dependencies
+#### Caching Gradle dependencies
 ```yaml
 steps:
 - uses: actions/checkout@v4
@@ -148,7 +150,7 @@ steps:
 - run: ./gradlew build --no-daemon
 ```
 
-#### Caching maven dependencies
+#### Caching Maven dependencies
 ```yaml
 steps:
 - uses: actions/checkout@v4
@@ -178,6 +180,21 @@ steps:
   run: sbt package
 ```
 
+#### Caching Mill dependencies
+```yaml
+steps:
+- uses: actions/checkout@v4
+- uses: actions/setup-java@v4
+  with:
+    distribution: 'temurin'
+    java-version: '21'
+    cache: 'mill'
+    cache-dependency-path: | # optional
+      sub-project/build.sc
+- name: Build with Mill
+  run: ./mill _.compile
+```
+
 #### Cache segment restore timeout
 Usually, cache gets downloaded in multiple segments of fixed sizes. Sometimes, a segment download gets stuck, which causes the workflow job to be stuck. The cache segment download timeout [was introduced](https://github.com/actions/toolkit/tree/main/packages/cache#cache-segment-restore-timeout) to solve this issue as it allows the segment download to get aborted and hence allows the job to proceed with a cache miss. The default value of the cache segment download timeout is set to 10 minutes and can be customized by specifying an environment variable named `SEGMENT_DOWNLOAD_TIMEOUT_MINS` with a timeout value in minutes.
 

__tests__/cache.test.ts

@@ -201,6 +201,48 @@ describe('dependency cache', () => {
         expect(firstCall).not.toBe(thirdCall);
       });
     });
+    describe('for mill', () => {
+      it('throws error if no build.sc found', async () => {
+        await expect(restore('mill', '')).rejects.toThrow(
+          `No file in ${projectRoot(
+            workspace
+          )} matched to [**/build.sc,**/*.sc,**/mill,**/.mill-version,**/.config/mill-version], make sure you have checked out the target repository`
+        );
+      });
+      it('downloads cache', async () => {
+        createFile(join(workspace, 'build.sc'));
+
+        await restore('mill', '');
+        expect(spyCacheRestore).toHaveBeenCalled();
+        expect(spyGlobHashFiles).toHaveBeenCalledWith(
+          '**/build.sc\n**/*.sc\n**/mill\n**/.mill-version\n**/.config/mill-version'
+        );
+        expect(spyWarning).not.toHaveBeenCalled();
+        expect(spyInfo).toHaveBeenCalledWith('mill cache is not found');
+      });
+      it('detects scala and mill changes under **/mill-build/ folder', async () => {
+        createFile(join(workspace, 'build.sc'));
+        createDirectory(join(workspace, 'project'));
+        createFile(join(workspace, '.config/mill-version'));
+
+        await restore('mill', '');
+        const firstCall = spySaveState.mock.calls.toString();
+
+        spySaveState.mockClear();
+        await restore('mill', '');
+        const secondCall = spySaveState.mock.calls.toString();
+
+        // Make sure multiple restores produce the same cache
+        expect(firstCall).toBe(secondCall);
+
+        spySaveState.mockClear();
+        createFile(join(workspace, '.mill-version'));
+        await restore('mill', '');
+        const thirdCall = spySaveState.mock.calls.toString();
+
+        expect(firstCall).not.toBe(thirdCall);
+      });
+    });
     it('downloads cache based on versions.properties', async () => {
       createFile(join(workspace, 'versions.properties'));
 

__tests__/cache/mill/.gitignore

@@ -0,0 +1 @@
+out/

__tests__/cache/mill/.mill-version

@@ -0,0 +1 @@
+0.12.3

__tests__/cache/mill/build.sc

@@ -0,0 +1,12 @@
+package build
+import mill._, scalalib._
+
+object MyProject extends ScalaModule {
+    def scalaVersion = "2.13.11"
+    def ivyDeps = Agg(ivy"com.lihaoyi::mainargs:0.6.2")
+
+    object test extends ScalaTests {
+        def ivyDeps = Agg(ivy"com.lihaoyi::utest:0.8.5")
+        def testFramework = "utest.runner.Framework"
+    }
+}

__tests__/cache/mill/mill

@@ -0,0 +1,26 @@
+#!/usr/bin/env sh
+# This is a wrapper script that automatically downloads Mill from GitHub.
+set -e
+
+if [ -z "$MILL_VERSION" ] ; then
+    MILL_VERSION="$(head -n 1 .mill-version 2> /dev/null)"
+fi
+
+MILL_DOWNLOAD_PATH="$HOME/.cache/mill/download"
+MILL_EXEC_PATH="${MILL_DOWNLOAD_PATH}/$MILL_VERSION"
+
+if [ ! -x "$MILL_EXEC_PATH" ] ; then
+    mkdir -p "${MILL_DOWNLOAD_PATH}"
+    DOWNLOAD_FILE=$MILL_EXEC_PATH-tmp-download
+    MILL_DOWNLOAD_URL="https://github.com/lihaoyi/mill/releases/download/${MILL_VERSION%%-*}/$MILL_VERSION-assembly"
+    curl --fail -L -o "$DOWNLOAD_FILE" "$MILL_DOWNLOAD_URL"
+    chmod +x "$DOWNLOAD_FILE"
+    mv "$DOWNLOAD_FILE" "$MILL_EXEC_PATH"
+    unset DOWNLOAD_FILE
+    unset MILL_DOWNLOAD_URL
+fi
+
+unset MILL_DOWNLOAD_PATH
+unset MILL_VERSION
+
+exec "${MILL_EXEC_PATH}" "$@"

src/cache.ts

@@ -13,7 +13,7 @@ const CACHE_MATCHED_KEY = 'cache-matched-key';
 const CACHE_KEY_PREFIX = 'setup-java';
 
 interface PackageManager {
-  id: 'maven' | 'gradle' | 'sbt';
+  id: 'maven' | 'gradle' | 'sbt' | 'mill';
   /**
    * Paths of the file that specify the files to cache.
    */
@@ -60,6 +60,21 @@ const supportedPackageManager: PackageManager[] = [
       '**/project/**.scala',
       '**/project/**.sbt'
     ]
+  },
+  {
+    id: 'mill',
+    path: [
+      join(os.homedir(), '.cache', 'mill')
+    ],
+    pattern: [
+      // https://github.com/coursier/cache-action/blob/4e2615869d13561d626ed48655e1a39e5b192b3c/README.md?plain=1#L28-L38
+      '**/build.sc',
+      '**/*.sc',
+      '**/mill',
+      '**/.mill-version',
+      // https://github.com/com-lihaoyi/mill/blob/5b88d1e268e6264e44589c5ac82c0fdbd680fd63/mill#L6-L11
+      '**/.config/mill-version'
+    ]
   }
 ];