70 lines
2.6 KiB
Markdown
70 lines
2.6 KiB
Markdown
# Hacking on Dune
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This section is for people who want to work on Jbuilder itself.
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## Bootstrap
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In order to build itself, Jbuilder uses an OCaml script
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([bootstrap.ml](bootstrap.ml)) that dumps most of the sources of Jbuilder into a
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single `boot.ml` file. This file is built using `ocamlopt` or `ocamlc`
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and used to build everything else.
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Note that we don't include all of the sources in boot.ml. We skip a
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few parts to speed up the build. In particular:
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- vendored libraries are replaced by simpler implementations taken
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from `vendor/boot`
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- a few files in `src` have an alternative version. These alternatives
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versions are named `XXX.boot.EXT`. For instance: `glob_lexer.boot.ml`
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## OCaml compatibility test
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Install opam switches for all the entries in the
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[jbuild-workspace.dev](jbuild-workspace.dev) file and run:
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```sh
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$ make all-supported-ocaml-versions
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```
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## Repository organization
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- `vendor/` contains dependencies of Jbuilder, that have been vendored
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- `plugin/` contains the API given to `jbuild` files that are OCaml
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scripts
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- `src/` contains the core of `Jbuilder`, as a library so that it can
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be used to implement the Jenga bridge later
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- `bin/` contains the command line interface
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- `doc/` contains the manual and rules to generate the manual pages
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## Design
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Jbuilder was initially designed to sort out the public release of Jane
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Street packages which became incredibly complicated over time. It is
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still successfully used for this purpose.
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One necessary feature to achieve this is the ability to precisely
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report the external dependencies necessary to build a given set of
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targets without running any command, just by looking at the source
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tree. This is used to automatically generate the `<package>.opam`
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files for all Jane Street packages.
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To implement this, the build rules are described using a build arrow,
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which is defined in [src/build.mli](src/build.mli). In the end it makes the
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development of the internal rules of Jbuilder very composable and
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quite pleasant.
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To deal with process multiplexing, Jbuilder uses a simplified
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Lwt/Async-like monad, implemented in [src/future.mli](src/future.mli).
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## Code flow
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- [src/jbuild.mli](src/jbuild.mli) contains the internal representation
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of `jbuild` files and the parsing code
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- [src/jbuild_load.mli](src/jbuild_load.mli) contains the code to scan
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a source tree and build the internal database by reading
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the `jbuild` files
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- [src/gen_rules.mli](src/gen_rules.mli) contains all the build rules
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of Jbuilder
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- [src/build_system.mli](src/build_system.mli) contains a trivial
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implementation of a Build system. This is what Jenga will provide
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when implementing the bridge
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