Update to JDK 17 (#1394)

Everything still targets JDK 8 (non-records) or JDK 16 (records only)

.github/workflows/build.yml

@@ -10,8 +10,6 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        java-version:
-          - 16
         use-ksp: [ true, false ]
 
     steps:
@@ -27,19 +25,19 @@ jobs:
       - uses: actions/cache@v2
         with:
           path: ~/.gradle/caches
-          key: ${{ runner.os }}-gradle-${{ matrix.java-version }}-${{ hashFiles('checksum.txt') }}
+          key: ${{ runner.os }}-gradle-${{ hashFiles('checksum.txt') }}
           restore-keys: |
-            ${{ runner.os }}-gradle-${{ matrix.java-version }}-
+            ${{ runner.os }}-gradle-
 
       - name: Configure JDK
         uses: actions/setup-java@v2
         with:
           distribution: 'zulu'
-          java-version: ${{ matrix.java-version }}
+          java-version: '17'
 
       - name: Test
         run: ./gradlew build check --stacktrace -PuseKsp=${{ matrix.use-ksp }}
 
       - name: Publish (default branch only)
-        if: github.repository == 'square/moshi' && github.ref == 'refs/heads/master' && matrix.java-version == '16'
+        if: github.repository == 'square/moshi' && github.ref == 'refs/heads/master'
         run: ./gradlew publish -PmavenCentralUsername=${{ secrets.SONATYPE_NEXUS_USERNAME }} -PmavenCentralPassword=${{ secrets.SONATYPE_NEXUS_PASSWORD }}

build.gradle.kts

@@ -112,7 +112,7 @@ subprojects {
   pluginManager.withPlugin("java") {
     configure<JavaPluginExtension> {
       toolchain {
-        languageVersion.set(JavaLanguageVersion.of(16))
+        languageVersion.set(JavaLanguageVersion.of(17))
       }
     }
     if (project.name != "records-tests") {

moshi/build.gradle.kts

@@ -29,9 +29,10 @@ val java16 by sourceSets.creating {
 }
 
 tasks.named<JavaCompile>("compileJava16Java") {
+  // We use JDK 17 for latest but target 16 for maximum compatibility
   javaCompiler.set(
     javaToolchains.compilerFor {
-      languageVersion.set(JavaLanguageVersion.of(16))
+      languageVersion.set(JavaLanguageVersion.of(17))
     }
   )
   options.release.set(16)

moshi/records-tests/build.gradle.kts

@@ -18,7 +18,14 @@ plugins {
   `java-library`
 }
 
+java {
+  toolchain {
+    languageVersion.set(JavaLanguageVersion.of(17))
+  }
+}
+
 tasks.withType<JavaCompile>().configureEach {
+  // Target 16 to ensure minimum compatibility
   options.release.set(16)
 }