n2o5

Under construction. Expect hiccups and unfinished parts.

A build system as library.

n2o5 is an idea grew out of fiddling n2. Less ninjutsu, more oxidizer.

Design & rationale

For low-level build graph executors like Make and Ninja, the build graph itself is implicit, based on artifacts generated by each build command. However, when writing build systems for high-level languages, it's often easier to think in the relationship between build command themselves, instead of writing the artifacts they generate and parsing it back to the graph.

n2o5 is a project that tries to explore build system design ideas from here:

• An embedded build graph executor that runs in-memory graphs.
• Works directly on build nodes and the edges connecting them. Files are only for determining the up-to-dateness of nodes.
• Build environment agnostic. Mock the world if you like.
• First-class callbacks as build commands.

n2o5 also differs from n2 significantly. In particular, n2o5 is not optimized for Ninja compatibility, and aims for better ergonomics as a library & in-memory graph usage.

Overridable

n2o5 provides overridable implementations to accommodate different build environments and needs.

Worlds (file system and process spawning):

• n2o5::LocalWorld -- The default world implementation, working on the local file system and process space.
• (Test only) tests/mock.rs::MockWorld -- A mocked world for testing.

Databases (build state cache):

• n2o5::db::in_memory::InMemoryDb -- An in-memory database implementation, mainly for testing, but can be used for ephemeral builds.
• n2o5_redb::ExecRedb -- A redb-backed filesystem database implementation.
• n2o5_heed::ExecHeedDb -- A LMDB(via heed)-backed filesystem database implementation. (Untested)

Progress (build status reporting):

• n2o5::progress::noop::NoopProgress -- Does nothing at all.
• n2o5::progress::dumb::DumbConsoleProgress -- An append-only console progress reporter.

CLI and ninja

The n2o5 commandline executable, located in cli/, is used for testing and stressing the library. It contains a subset of ninja for testing with the library and tweaking on ergonomics.

You may use it either as n2o5 ninja [ninja_args...] or create a symlink whose name starts with ninja and use it as a replacement.

Unsupported features:

• Dry run
• Printing commands executed
• Advanced ninja features like pools, response files, depfile/dyndep, etc.

License

MPL 2.0

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Originally this project was called n2o4. However, this name has been taken by n2o4, a binding to NASA's Core Flight System, which definitely deserves the name. It has thus been renamed to n2o5.