114 lines
5.4 KiB
Markdown
114 lines
5.4 KiB
Markdown
# Gradle Version
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**Status:**
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- proposed: 2026-06-09
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- accepted: -
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- rejected: -
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- superseded: -
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**Decision [proposed]:** Gradle 8.14 — minimum required by Spring Boot 4.0; Gradle 9 deferred until openapi-generator and ktlint-gradle confirm compatibility.
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## Context and Problem Statement
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GitTally is a greenfield Kotlin/Spring Boot project.
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A Gradle version must be chosen for the initial setup.
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[Gradle 9](https://docs.gradle.org/9.3.0/release-notes.html) (currently 9.5.1) is now stable and available.
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The question is whether it is the right choice at project start, or whether staying on Gradle 8.x is safer.
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### Technical Background
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**Configuration Cache** is a Gradle feature that serializes the result of the *configuration phase*
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(evaluating all build scripts, resolving plugins, building the task graph) so that subsequent
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builds can skip it entirely.
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In large projects the configuration phase alone can take tens of seconds;
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caching it makes every incremental build substantially faster.
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In Gradle 8.x Configuration Cache is opt-in.
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In Gradle 9 it is stable and **mandatory**: any plugin that reads mutable environment state or
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modifies the project model after configuration will fail hard rather than emit a warning.
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This enforcement fixed longstanding correctness issues across the ecosystem,
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but it also means any plugin that has *not* been updated will break the build outright.
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The Gradle version choice is not isolated to the build tool itself.
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It has a direct dependency chain:
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- [Gradle 9](https://docs.gradle.org/current/userguide/compatibility.html) is officially
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supported by Spring Boot 4.0 only.
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Spring Boot 4.0 also requires Gradle 8.14 as a minimum for the 8.x line.
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- [Spring Boot 4.0](https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-4.0-Release-Notes)
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requires Spring Framework 7 and Jakarta EE 11 — a generation step up from Spring Boot 3.x
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(Spring Framework 6, Jakarta EE 10).
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- Plugin ecosystem readiness varies: the
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[openapi-generator Gradle plugin](https://github.com/OpenAPITools/openapi-generator/issues/22084)
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has a known Gradle 9 issue in its generated build files, and
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[ktlint-gradle 12.1.1](https://github.com/JLLeitschuh/ktlint-gradle) Gradle 9 support
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needs verification.
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- The [`io.spring.dependency-management` plugin](https://github.com/spring-gradle-plugins/dependency-management-plugin)
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used to resolve the Spring BOM has known friction with Gradle 9
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and would need to be replaced by a native `platform()` import.
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The Spring Boot version decision (ADR 0003) concluded that Spring Boot 4.0 is required.
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Spring Boot 4.0 mandates Gradle 8.14 as minimum, meaning a wrapper upgrade from the
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current 8.8 is necessary regardless of whether Gradle 9 is chosen.
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## Considered Options
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* Gradle 8.14 (minimum for Spring Boot 4.0)
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* Gradle 9.x
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### [Gradle 8.x](https://docs.gradle.org/8.8/release-notes.html)
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The currently configured series (wrapper at 8.8, to be bumped to 8.14+ for Spring Boot 4.0).
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#### Advantages
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- Plugin compatibility is well understood for ktlint-gradle and openapi-generator-gradle-plugin.
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- Configuration Cache is opt-in — teams can enable it incrementally and diagnose failures
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without blocking the build.
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- Lower risk for adopting spec-first OpenAPI:
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the [openapi-generator-gradle-plugin](https://github.com/OpenAPITools/openapi-generator/issues/22084)
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has a known Gradle 9 incompatibility in generated build files.
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#### Disadvantages
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- Not on the current Gradle major line; the Configuration Cache benefits are not enforced.
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- An eventual migration to Gradle 9 will still be needed.
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### [Gradle 9.x](https://docs.gradle.org/9.3.0/release-notes.html)
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The current major release (9.5.1 as of May 2026), officially supported alongside Spring Boot 4.0.
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#### Advantages
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- Aligns with the latest Spring Boot generation in a fully supported pairing.
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- Configuration Cache is mandatory: faster incremental builds and build-script correctness
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is enforced across the whole plugin chain — problems surface immediately rather than silently.
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- `io.spring.dependency-management` plugin is replaced by cleaner native `platform()` BOM import.
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- Greenfield is the easiest moment to adopt it; no migration debt later.
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#### Disadvantages
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- [openapi-generator-gradle-plugin](https://github.com/OpenAPITools/openapi-generator/issues/22084)
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has a known Gradle 9 issue in generated `build.gradle` files; impact on the spec-first
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code generation task specifically needs verification.
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- [ktlint-gradle 12.1.1](https://github.com/JLLeitschuh/ktlint-gradle) Gradle 9 support
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needs verification.
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- Configuration Cache mandatory means any currently uncached plugin will break the build
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until updated, complicating initial setup.
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## Decision Outcome
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**Gradle 8.14** (latest stable 8.x) is chosen over Gradle 9 for the initial setup.
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The main reasons:
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- Spring Boot 4.0 requires Gradle 8.14 as minimum; upgrading from 8.8 is necessary in any case.
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- Gradle 9 is technically compatible with Spring Boot 4.0, but the mandatory Configuration Cache
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creates unacceptable risk until the openapi-generator-gradle-plugin Gradle 9 compatibility
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is confirmed (see [issue #22084](https://github.com/OpenAPITools/openapi-generator/issues/22084)).
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- ktlint-gradle 12.1.1 Gradle 9 support is unverified; a formatter breaking the build on day
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one is a poor start.
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Upgrade trigger: revisit Gradle 9 once openapi-generator and ktlint-gradle confirm support.
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The upgrade itself will be low-risk at that point since the Spring Boot 4.0 step is already done.
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