daml/daml-foundations/daml-ghc

DAML-GHC Project

The DAML 1.2 compiler, converting DAML as a dialect embedded into Haskell to DAML-LF.

Compiling code

The code includes a simple CLI that compiles a given (main) DAML-1.2 file to LF.

-- Reserved for future use?

See the --help text for details.

Developing

Before you start, build the IDE test suite. We fall back to this to find runfiles such as the scenario service and the package database when we’re running inside GHCi.

bazel build //daml-foundations/daml-ghc:daml-ghc-shake-test-ci

When working on the compiler:

da-ghcid //daml-foundations/daml-ghc:daml-ghc-test-newest --reload=daml-foundations/daml-ghc/tests --test=":main --pattern="
bazel run //daml-foundations/daml-ghc:daml-ghc-test-newest -- --pattern=
bazel run damlc -- compile $PWD/MyDaml12File.daml

When working on the IDE via the test suite:

bazel run //daml-foundations/daml-ghc:daml-ghc-shake-test-ci -- --pattern=
da-ghcid daml-foundations/daml-ghc/src/DA/Test/ShakeIdeClient.hs --test=":main --pattern="

Testing in situ:

da-sdk-head
da-sdk-head --damlc

Documentation

Standard library docs are exposed under the bazel rules which you can build with:

bazel build //daml-foundations/daml-ghc:daml-base-rst-docs
bazel build //daml-foundations/daml-ghc:daml-base-hoogle-docs

Until we have fully automated doc generation, you can copy them out manually into the repo with the command:

cd ~/projects/daml
cp bazel-genfiles/daml-foundations/daml-ghc/daml-base-hoogle.txt docs/daml/stdlib/static/base.txt
cp bazel-genfiles/daml-foundations/daml-ghc/daml-base.rst docs/daml/stdlib/base.rst
cp bazel-genfiles/daml-foundations/daml-ghc/daml-base.rst daml-foundations/daml-stdlib/doc/source/base.rst

You can preview the results with:

cd ~/projects/daml/daml-foundations/daml-stdlib/doc
da-doc-preview

To see your changes, rebuild with bazel, rerun the last cp command, and visit the result at http://localhost:8081/base.html

Deploying ghc-lib

Consult nix/overrides/ghc-lib/README.md for details on the ghc-lib nix package and how to test it.

DAML Packages and Database

A DAML project is compiled to a DAML package and can be distributed as a DAML archive (DAR). This is essentially a zip archive containing the DAML source code of the library together with the compiled .dalf file. A full specification of the DAML archive format can be found in daml-foundations/daml-tools/docs/daml-project/source/reference.rst. The daml-ghc package loading mechanism is based on GHC's package database and uses the same .conf file format. GHC's package database is documented at https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/packages.html.

Installing a package

Currently there is no tooling for installing packages and the process is manual. Let's assume you want to install a DAML archive example with the following directory structure:

example
├── DA
│   └── NewLibrary.daml
├── example.dalf
└── LibraryModules.daml

To install the DAML package example.dar into a package database directory, unzip the DAR file and compile the LibraryModules.daml file with

unzip example.dar
cd example
bazel run damlc -- compile --package=example LibraryModules.daml -o example_compiled.dalf

Note that you need to specify the package name with the --package flag. The contained example.dalf and the just compiled example_compiled.dalf DAML-LF files need to be the same file, otherwise your archive is either corrupted or has been compiled with a different compiler. Copy all the created files, in particular the created .hi interface files, to your package database directory:

cd ..
cp -a example <package-db>/

Within the package database directory create a example.conf file with the following content:

name: example
version: 1.0.0
id: example
key: example
copyright: 2015-2019 Digital Asset Holdings
maintainer: Digital Asset
exposed: True
exposed-modules: <your exposed modules of the library>
import-dirs: example/
library-dirs: example/
data-dir: example/
depends: <dependencies on other packages>

Update the package cache with

ghc-pkg recache --package-db .

This creates a package.cache and a package.cache.lock file.

Loading packages

daml-ghc loads packages from a package database given by the option --package-db. It creates a map from package name to DAML-LF file from all the contained .dalf files in this directory and links the created DAML-LF against these packages. It uses the .hi interface files created upon installation of the packages for type checking.

Base packages

Currently a package database containing the single package daml-prim is provided together with the damlc Bazel rule and bazel run damlc loads this database by default. This package database is also shipped together with da-hs-damli-app.tar.gz and da-hs-damlc-app.tar.gz for the SDK and the platform and is contained in the directory resources/package-db/gen/. The source of the daml-prim package is found in the daml-foundations/daml-ghc/daml-prim directory.

Building the package database

The package database that comes with daml-ghc and the above archives can be build with

bazel build //daml-foundations/daml-ghc/package-database:package-db

and the daml-prim.dalf for the daml-prim packge with

bazel build //daml-foundations/daml-ghc/package-database:daml-prim.dalf

The daml-blessed tag

We should update the daml-blessed tag semi regularly. If you are asked to do that:

• Check when daml-blesed was last updated, usually don't continue if it was recently
• Create a tag: git tag -f -a daml-blessed -m "Creation of daml-blessed following the test plan"
• Push it: git push --force origin daml-blessed