https://github.com/tadfisher/gradle2nix
Generate Nix expressions which build Gradle-based projects.
https://github.com/tadfisher/gradle2nix
gradle nix nixos nixpkgs
Last synced: 6 days ago
JSON representation
Generate Nix expressions which build Gradle-based projects.
- Host: GitHub
- URL: https://github.com/tadfisher/gradle2nix
- Owner: tadfisher
- License: mit
- Created: 2019-04-01T16:26:33.000Z (over 6 years ago)
- Default Branch: master
- Last Pushed: 2025-08-22T22:43:27.000Z (about 2 months ago)
- Last Synced: 2025-08-23T00:36:24.096Z (about 2 months ago)
- Topics: gradle, nix, nixos, nixpkgs
- Language: Kotlin
- Homepage:
- Size: 1.95 MB
- Stars: 133
- Watchers: 6
- Forks: 63
- Open Issues: 47
-
Metadata Files:
- Readme: README.org
- License: COPYING
Awesome Lists containing this project
README
#+STARTUP: inlineimages
[[./assets/gradle2nix.png]]
Generate [[https://nixos.org/nix/][Nix]] expressions which build [[https://gradle.org/][Gradle]]-based projects.
** Why?
Nix is an OS-agnostic package manager, a language-agnostic build
system, and a bespoke programming language. One of its unique features
is that it is purely functional; a "package" is a function which
accepts inputs (source code, configuration, etc) and produces an
output (binaries, a Java JAR, documentation, really anything).
One benefit of a functional build system is [[https://reproducible-builds.org/][reproducibility]]. If you
specify your inputs precisely, and take care not to introduce
impurities—such as files retrieved over a network without tracking
their content—you will receive, byte-for-byte, the exact output as
someone else running the same function over the same inputs.
Gradle is not a functional build system. Most Gradle-based projects
will produce highly variable outputs depending on a host of impure
inputs, including:
- The JVM hosting the build
- The Gradle installation running the build
- Any usage of dynamic version constraints for dependencies
- SNAPSHOT dependencies
- Environment variables and command-line options
- Artifacts cached on the system hosting the build
=gradle2nix= helps to solve this problem by leveraging Nix to control
the most common inputs to a Gradle build. When run on a project, it
will record all dependencies for both the build environment (including
=plugins= and =buildscript= blocks) and the project, and provide a Nix
expression to run the build given these dependencies. The build itself
is then run in a sandbox, where only content-tracked network requests
are allowed to fetch dependencies, and a local Maven repository is
created on-the-fly to host the dependency artifacts somewhere Gradle
can resolve them without a network.
This tool is useful for both development and packaging. You can use
=gradle2nix= to:
- Create isolated and reproducible development environments that work
anywhere Nix itself can run;
- Reduce or eliminate flakiness and maintenance headaches from CI/CD
pipelines
- Distribute a recipe which can reliably build a Gradle project in
repositories such as the [[https://nixos.org/nixpkgs/][Nix Package Collection]].
** Installation
A [[./default.nix][Nix expression]] (generated by =gradle2nix= itself) is provided for
convenience. The following expression will fetch and build the latest
version of this package:
#+begin_src nix
import (fetchTarball "https://github.com/tadfisher/gradle2nix/archive/master.tar.gz") {}
#+end_src
If this expression is in, say, =gradle2nix.nix=, =gradle2nix= can be
built and placed in =.//result= with the following:
#+begin_example
nix build -f gradle2nix.nix
#+end_example
You can also use the following one-liners to build or install
=gradle2nix= in your user profile:
#+begin_example
# Build and place in ./result/
nix build -f "https://github.com/tadfisher/gradle2nix/archive/master.tar.gz"
# Build and install in the user profile
nix-env -if "https://github.com/tadfisher/gradle2nix/archive/master.tar.gz"
#+end_example
=gradle2nix= is not yet packaged in =nixpkgs= itself, but work is
[[https://github.com/NixOS/nixpkgs/pull/77422][in progress]].
*** Flake (experimental)
A [[./flake.nix][flake.nix]] is provided for those using [[https://nixos.wiki/wiki/Flakes][Nix flakes]]. For example, the
following will build and run =gradle2nix= with the arguments provided
after =--=:
#+begin_example
nix run github:tadfisher/gradle2nix -- --help
#+end_example
** Usage
#+begin_example
Usage: gradle2nix [OPTIONS] [PROJECT-DIR]
Options:
-g, --gradle-version VERSION Use a specific Gradle version
-a, --gradle-args ARGS Extra arguments to pass to Gradle
-c, --configuration NAME Add a configuration to resolve (default:
all configurations)
-i, --include DIR Add an additional project to include
-p, --project PATH Only resolve these subproject paths, e.g.
':', or ':sub:project' (default: all
projects)
-o, --out-dir DIR Path to write generated files (default:
PROJECT-DIR)
-e, --env FILENAME Prefix for environment files (.json and
.nix) (default: gradle-env)
-b, --build-src / -nb, --no-build-src
Include buildSrc project (default: true)
-q, --quiet Disable logging
-h, --help Show this message and exit
Arguments:
PROJECT-DIR Path to the project root (default: .)
#+end_example
Simply running =gradle2nix= in the root directory of a project should
be enough for most projects. This will produce two files, by default
called =gradle-env.json= and =gradle-env.nix=, which contain the
pinned dependencies for the project and a standard build expression
which can be imported or called by other Nix expressions. An example
of such an expression can be found in this project's [[./default.nix][default.nix]].
*** Specifying the Gradle version
By default, if the project has configured the Gradle wrapper, that
version will be detected and pinned; otherwise, the version of Gradle
installed on your system will be pinned. You can override this with
the =--gradle-version= argument, which also avoids the need to have
Gradle installed.
#+begin_example
gradle2nix -g 6.1
#+end_example
*** Multi-project builds
If you want to resolve only a subset of projects in a [[https://docs.gradle.org/current/userguide/intro_multi_project_builds.html][multi-project
build]], add the =--project= option for each project. For example, in a
project where you only want to build the subprojects =:app= and
=:widget=:
#+begin_example
gradle2nix -p :app -p :widget
#+end_example
Any [[https://docs.gradle.org/current/userguide/declaring_dependencies.html#sub:project_dependencies][project dependencies]] will be also be included when pinning
dependency artifacts.
** Contributing
Bug reports and feature requests are encouraged.
[[https://github.com/tadfisher/gradle2nix/issues/new][Create an issue]]
Code contributions are also encouraged. Please review the test cases
in the [[./fixtures][fixtures]] directory and create a new one to reproduce any fixes
or test new features. See the [[./plugin/src/compatTest/kotlin/org/nixos/gradle2nix][existing compatibility tests]] for
examples of testing with these fixtures.
** License
=gradle2nix= is licensed under the [[./COPYING][MIT License]].