Upgrade dependencies and toolchain; refresh project docs

.github/workflows/ci.yml

@@ -17,11 +17,11 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
-      - name: Set up JDK 17
+      - name: Set up JDK 25
         uses: actions/setup-java@v4
         with:
           distribution: temurin
-          java-version: 17
+          java-version: 25
 
       - name: Set up Gradle
         uses: gradle/actions/setup-gradle@v4
@@ -45,11 +45,11 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
-      - name: Set up JDK 17
+      - name: Set up JDK 25
         uses: actions/setup-java@v4
         with:
           distribution: temurin
-          java-version: 17
+          java-version: 25
 
       - name: Set up Gradle
         uses: gradle/actions/setup-gradle@v4

CHANGELOG.md

@@ -7,18 +7,32 @@ adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 ## [Unreleased]
 
 ### Added
-- Kotlinter Gradle plugin (`org.jmailen.kotlinter` 5.4.2) wired into the build for Kotlin lint and formatting.
-- Detekt Gradle plugin (`dev.detekt` 2.0.0-alpha.3) with a `detekt { ... }` configuration block.
+- Kotlinter Gradle plugin (`org.jmailen.kotlinter` 5.5.0) wired into the build for Kotlin lint and formatting.
+- Detekt Gradle plugin (`dev.detekt` 2.0.0-alpha.5) with a `detekt { ... }` configuration block.
 - `.editorconfig` pinning charset, end-of-line, indent style, and ktlint rule overrides so kotlinter aligns with the project's existing Kotlin style.
-- Makefile targets: `help` (self-documenting target list), `lint`, `format`, `detekt`, `detekt-baseline`.
+- GitHub Actions CI (`.github/workflows/ci.yml`) running `make lint` and `make tests` as parallel jobs on every push and pull request to `master`, with Gradle caching, concurrency cancellation, and uploaded lint/test reports.
+- Makefile targets: `help` (self-documenting target list), `lint`, `format`, `detekt`, `detekt-baseline`, `versions`, `upgrade-wrapper`.
 - Makefile guard `_require-gradle-version` that fails fast if the Gradle version cannot be read from `gradle/libs.versions.toml`.
 
 ### Changed
-- Bumped `readingbat-core` to 3.1.8.
+- Raised the JVM toolchain from Java 17 to Java 25 (`jvm` in `gradle/libs.versions.toml`).
+- Upgraded the Gradle wrapper from 9.5.0 to 9.6.1.
+- Bumped dependencies: Kotlin → 2.4.0, Ktor → 3.5.1, Kotest → 6.2.1, `readingbat-core` → 3.2.1, `common-utils` → 2.9.3, `kotlin-logging` → 8.0.4, kotlinter → 5.5.0, detekt → 2.0.0-alpha.5.
+- Refactored `build.gradle.kts` into per-concern helper functions (`configureKotlin`, `configureDetekt`, `configureKotlinter`, `configureKtor`, `configureShadowJar`, `configureTest`, `configureVersions`).
+- Enabled the Kotlin unused-return-value checker (`-Xreturn-value-checker=check`) on production code only (the test source set is excluded to avoid false positives from Kotest's fluent assertions).
+- Build the fat jar via Ktor's `fatJar` task; the `dependencyUpdates` check now rejects pre-release candidates for dependencies currently on a stable version.
+- Renamed the `gradle` version key to `gradle-wrapper` in `gradle/libs.versions.toml`.
+- Renamed the Makefile `versioncheck` target to `versions`, made `help` the default target, and added `--no-configuration-cache --no-parallel` to the dependency-update check.
 - `Content.kt` now imports `ReturnType` directly instead of `ReturnType.*`; all challenge registrations qualify return types (e.g., `ReturnType.IntType`).
 - Makefile `build` and `cc` targets use the canonical `-x test` flag instead of `-xtest`.
 - Reordered `.PHONY` to match the in-file target definition order.
 
+### Removed
+- Makefile `heroku` and `logs` targets.
+
+### Fixed
+- `ContentTests` now calls `correctAnswers()` as a function, matching the upgraded `readingbat-kotest` API (previously a property).
+
 ## [Pre-Unreleased history]
 
 Prior changes were tracked only via Git history; see `git log` for details.

CLAUDE.md

@@ -62,13 +62,17 @@ make lint             # Run kotlinter (lintKotlin) + detekt
 make format           # Format Kotlin sources via formatKotlin
 make detekt           # Run detekt static analysis only
 make detekt-baseline  # Regenerate the detekt baseline file
-make versioncheck     # Check dependency updates
+make versions         # Check for dependency updates
 make upgrade-wrapper  # Upgrade Gradle wrapper
 make uberjar          # Build fat jar
 make uber             # Build and run fat jar (java -jar build/libs/server.jar)
 ```
 
-JVM toolchain: Java 17. Testing: Kotest with JUnit5 platform. Lint/format: kotlinter + detekt, configured via `.editorconfig` (ktlint rule overrides) and the `detekt { ... }` block in `build.gradle.kts`.
+JVM toolchain: Java 25 (set via `jvm` in `gradle/libs.versions.toml`, consumed by `jvmToolchain(...)` in `build.gradle.kts`). Testing: Kotest with JUnit5 platform. Lint/format: kotlinter + detekt, configured via `.editorconfig` (ktlint rule overrides) and the `detekt { ... }` block in `build.gradle.kts`.
+
+## Continuous Integration
+
+`.github/workflows/ci.yml` runs `make lint` and `make tests` as parallel jobs on every push and pull request to `master`, with Gradle caching, concurrency cancellation, and uploaded lint/test reports.
 
 ## Adding a New Challenge
 

Makefile

@@ -1,5 +1,5 @@
 .PHONY: default help clean build lint format detekt detekt-baseline tests uberjar uber \
-		cc run heroku logs versions upgrade-wrapper _require-gradle-version
+		cc run versions upgrade-wrapper _require-gradle-version
 
 GRADLE_VERSION := $(shell sed -n 's/^gradle-wrapper = "\(.*\)"/\1/p' gradle/libs.versions.toml)
 
@@ -42,19 +42,13 @@ cc: ## Continuous compilation (no tests)
 run: ## Start the server on port 8080
 	./gradlew run
 
-heroku: ## Push master to Heroku
-	git push heroku master
-
-logs: ## Tail Heroku logs
-	heroku logs --tail
-
-# Gradle's documented upgrade procedure: the first run rewrites
-# gradle-wrapper.properties using the *old* wrapper jar; the second run
-# regenerates the wrapper itself with the new version.
 versions: ## Check for dependency updates (default target)
 	./gradlew dependencyUpdates --no-configuration-cache --no-parallel
 
-upgrade-wrapper: _require-gradle-version ## Upgrade Gradle wrapper to version in libs.versions.toml
+upgrade-wrapper: _require-gradle-version ## Upgrade the Gradle wrapper to the catalog version
+	# Gradle's documented upgrade procedure: the first run rewrites
+	# gradle-wrapper.properties using the *old* wrapper jar; the second run
+	# regenerates the wrapper itself with the new version.
 	./gradlew wrapper --gradle-version=$(GRADLE_VERSION) --distribution-type=bin
 	./gradlew wrapper --gradle-version=$(GRADLE_VERSION) --distribution-type=bin
 

README.md

@@ -4,7 +4,7 @@ Python programming challenges served by the [ReadingBat](https://github.com/read
 
 ## Prerequisites
 
-- Java 17+
+- Java 25+ (the Gradle toolchain targets Java 25; Gradle can auto-provision it)
 
 ## Setup
 

RELEASE_NOTES.md

@@ -1,36 +1,57 @@
 # Release Notes
 
-## Unreleased — Kotlinter, detekt, and Makefile help
+## Unreleased — tooling, CI, and dependency upgrades
 
-This release focuses on developer ergonomics and code-style enforcement. No
-runtime behavior, content, or public DSL has changed.
+This release focuses on developer ergonomics, continuous integration, and
+toolchain/dependency upgrades. No runtime behavior, content, or public DSL has
+changed.
 
 ### Highlights
 
-- **Kotlin linting and formatting.** The build now applies the
-  [kotlinter](https://github.com/jeremymailen/kotlinter-gradle) Gradle plugin.
-  Run `make lint` to check Kotlin sources, and `make format` to apply fixes.
+- **Kotlin linting and formatting.** The build applies the
+  [kotlinter](https://github.com/jeremymailen/kotlinter-gradle) Gradle plugin
+  (5.5.0). Run `make lint` to check Kotlin sources, and `make format` to apply
+  fixes.
 - **Detekt static analysis.** Detekt is wired up via the `dev.detekt` plugin
-  and a `detekt { ... }` block in `build.gradle.kts`. Use `make detekt` to run
-  it standalone, or `make detekt-baseline` to (re)generate the baseline.
+  (2.0.0-alpha.5) and a `detekt { ... }` block in `build.gradle.kts`. Use
+  `make detekt` to run it standalone, or `make detekt-baseline` to (re)generate
+  the baseline.
+- **GitHub Actions CI.** A new `.github/workflows/ci.yml` runs `make lint` and
+  `make tests` as parallel jobs on every push and pull request to `master`,
+  with Gradle caching, concurrency cancellation, and uploaded reports.
 - **Self-documenting Makefile.** Run `make help` for a colorized list of every
   target, generated from `## ` annotations in the Makefile itself.
-- **`.editorconfig`.** New file pinning charset, EOL, indent width, and the
-  set of ktlint rules disabled to match the existing Kotlin style.
-- **Dependency bump.** `readingbat-core` updated from 3.1.5 to 3.1.8.
+- **`.editorconfig`.** Pins charset, EOL, indent width, and the set of ktlint
+  rules disabled to match the existing Kotlin style.
+- **JVM toolchain → Java 25.** The Gradle toolchain now targets Java 25
+  (previously Java 17); Gradle can auto-provision it.
+- **Dependency upgrades.** Kotlin → 2.4.0, Ktor → 3.5.1, Kotest → 6.2.1,
+  `readingbat-core` → 3.2.1, `common-utils` → 2.9.3, `kotlin-logging` → 8.0.4.
+  The Gradle wrapper moved from 9.5.0 to 9.6.1.
+- **Build script cleanup.** `build.gradle.kts` is reorganized into per-concern
+  helper functions, the fat jar is built via Ktor's `fatJar` task, the Kotlin
+  unused-return-value checker runs over production code, and `dependencyUpdates`
+  now filters out pre-release candidates for stable dependencies.
 
 ### Source-level changes
 
 - `Content.kt` no longer wildcard-imports `ReturnType.*`; all return types are
   qualified (e.g., `ReturnType.IntType`). When adding new challenges, use the
   qualified form.
+- The `gradle` version key in `gradle/libs.versions.toml` was renamed to
+  `gradle-wrapper`.
+- The Makefile `versioncheck` target was renamed to `versions`, `help` is now
+  the default target, and the dependency-update check runs with
+  `--no-configuration-cache --no-parallel`.
 - The Makefile uses the canonical `-x test` flag (with a space) in `build` and
   `cc` targets, replacing the deprecated `-xtest` short form.
 
 ### Upgrade notes
 
+- Java 25 is now the toolchain target. Gradle will auto-provision a matching
+  JDK; ensure toolchain auto-download is enabled or a Java 25 JDK is installed.
 - After pulling, run `./gradlew --refresh-dependencies` (or `make build`) once
-  so the new plugins resolve.
+  so the new plugins and dependencies resolve.
 - Existing developer workflows are unchanged; the new `lint` / `format`
   targets are optional but recommended before pushing.
 

build.gradle.kts

@@ -1,21 +1,24 @@
+import com.github.benmanes.gradle.versions.updates.DependencyUpdatesTask
+import org.gradle.api.tasks.testing.logging.TestExceptionFormat
 import org.gradle.api.tasks.testing.logging.TestLogEvent
+import org.gradle.kotlin.dsl.named
+import org.gradle.kotlin.dsl.withType
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
 
 plugins {
-  application
   alias(libs.plugins.kotlin.jvm)
   alias(libs.plugins.versions)
   alias(libs.plugins.ktor.plugin)
   alias(libs.plugins.detekt)
   alias(libs.plugins.kotlinter)
 }
 
-// This is for ./gradlew run
+description = "ReadingBat Site"
+
 application {
   mainClass = "ContentServerKt"
 }
 
-description = "ReadingBat Site"
-
 dependencies {
   implementation(libs.readingbat.core)
   implementation(libs.core.utils)
@@ -24,43 +27,102 @@ dependencies {
   testImplementation(libs.bundles.testing)
 }
 
-kotlin {
-  jvmToolchain(libs.versions.jvm.get().toInt())
+tasks.register("stage") {
+  group = "distribution"
+  description = "Clean-builds the project for deployment."
+  dependsOn("clean", "build")
 }
 
-detekt {
-  source.setFrom("src/main/kotlin", "src/test/kotlin")
-  buildUponDefaultConfig = true
-  parallel = true
+tasks.named("build") {
+  mustRunAfter("clean")
 }
 
-kotlinter {
-  ignoreFormatFailures = false
-  ignoreLintFailures = false
-  reporters = arrayOf("checkstyle", "plain")
+configureKotlin()
+configureDetekt()
+configureKotlinter()
+configureKtor()
+configureShadowJar()
+configureTest()
+configureVersions()
+
+fun Project.configureKotlin() {
+  kotlin {
+    jvmToolchain(libs.versions.jvm.get().toInt())
+  }
+
+  // Run the unused-return-value checker over production code only. Kotest's
+  // assertion DSL (e.g. shouldBe) returns its receiver, and tests intentionally
+  // discard that result, so applying the checker to the test source set would
+  // emit only false-positive warnings.
+  tasks.named<KotlinCompile>("compileKotlin") {
+    compilerOptions {
+      freeCompilerArgs.add("-Xreturn-value-checker=check")
+    }
+  }
 }
 
-tasks.register("stage") {
-  dependsOn("clean", "build")
+fun Project.configureDetekt() {
+  detekt {
+    source.setFrom("src/main/kotlin", "src/test/kotlin")
+    buildUponDefaultConfig = true
+    parallel = true
+  }
 }
 
-tasks.named("build") {
-  mustRunAfter("clean")
+fun Project.configureKotlinter() {
+  kotlinter {
+    ignoreFormatFailures = false
+    ignoreLintFailures = false
+    reporters = arrayOf("checkstyle", "plain")
+  }
 }
 
-tasks.shadowJar {
-  archiveFileName.set("server.jar")
-  isZip64 = true
-  duplicatesStrategy = DuplicatesStrategy.EXCLUDE
-  listOf("META-INF/*.SF", "META-INF/*.DSA", "META-INF/*.RSA", "LICENSE*").forEach(::exclude)
+fun Project.configureKtor() {
+  ktor {
+    fatJar {
+      archiveFileName = "server.jar"
+    }
+  }
 }
 
-tasks.test {
-  useJUnitPlatform()
+fun Project.configureShadowJar() {
+  // Ktor's `buildFatJar` task delegates to shadow; this block configures that output.
+  tasks.shadowJar {
+    isZip64 = true
+    duplicatesStrategy = DuplicatesStrategy.WARN
+    exclude("META-INF/*.SF", "META-INF/*.DSA", "META-INF/*.RSA")
+  }
+}
+
+fun Project.configureTest() {
+  tasks.test {
+    useJUnitPlatform()
+
+    testLogging {
+      events = setOf(TestLogEvent.PASSED, TestLogEvent.SKIPPED, TestLogEvent.FAILED, TestLogEvent.STANDARD_ERROR)
+      exceptionFormat = TestExceptionFormat.FULL
+      showStandardStreams = false
+    }
+  }
+}
+
+fun Project.configureVersions() {
+  // A pre-release qualifier is a `.` or `-` delimiter followed by a known unstable
+  // keyword. `m\d` matches milestones (`-M1`/`.M2`) without catching stable classifiers
+  // like `-macos`/`-MR1`, and the `[.-]` delimiter catches both dash-style (`-alpha`)
+  // and dot-style (Netty's `.Beta1`) qualifiers while leaving `-jre`/`.Final` stable.
+  val preReleaseQualifier =
+    Regex("""[.-](rc|beta|alpha|m\d|cr|snapshot|eap|dev|milestone|pre)""", RegexOption.IGNORE_CASE)
+
+  fun isNonStable(version: String): Boolean = preReleaseQualifier.containsMatchIn(version)
 
-  testLogging {
-    events = setOf(TestLogEvent.PASSED, TestLogEvent.SKIPPED, TestLogEvent.FAILED, TestLogEvent.STANDARD_ERROR)
-    exceptionFormat = org.gradle.api.tasks.testing.logging.TestExceptionFormat.FULL
-    showStandardStreams = false
+  tasks.withType<DependencyUpdatesTask>().configureEach {
+    notCompatibleWithConfigurationCache("the dependency updates plugin is not compatible with the configuration cache")
+    // Reject a pre-release candidate only when the current version is stable. For
+    // dependencies we intentionally track on a pre-release line (e.g. a detekt
+    // alpha), newer pre-releases are still surfaced as available updates.
+    rejectVersionIf {
+      isNonStable(candidate.version) && !isNonStable(currentVersion)
+    }
   }
 }

gradle/libs.versions.toml

@@ -1,14 +1,14 @@
 [versions]
-detekt = "2.0.0-alpha.3"
-gradle-wrapper = "9.5.1"
-jvm = "17"
-kotest = "6.1.11"
+detekt = "2.0.0-alpha.5"
+gradle-wrapper = "9.6.1"
+jvm = "25"
+kotest = "6.2.1"
 kotlin = "2.4.0"
 kotlinter = "5.5.0"
-ktor = "3.5.0"
+ktor = "3.5.1"
 logging = "8.0.4"
-readingbat = "3.1.8"
-utils = "2.9.0"
+readingbat = "3.2.1"
+utils = "2.9.3"
 versions = "0.54.0"
 
 [libraries]

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-9.5.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-9.6.1-bin.zip
 networkTimeout=10000
 retries=0
 retryBackOffMs=500