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Merge pull request #142825 from cdepillabout/buildDhallUrl

dhallPackages.buildDhallUrl: add function for easily building dhall remote imports
This commit is contained in:
Dennis Gosnell 2021-11-08 13:44:37 +09:00 committed by GitHub
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6 changed files with 167 additions and 15 deletions

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@ -50,7 +50,7 @@ expression does not protect the Prelude import with a semantic integrity
check, so the first step is to freeze the expression using `dhall freeze`,
like this:
```bash
```ShellSession
$ dhall freeze --inplace ./true.dhall
```
@ -113,7 +113,7 @@ in
… which we can then build using this command:
```bash
```ShellSession
$ nix build --file ./example.nix dhallPackages.true
```
@ -121,7 +121,7 @@ $ nix build --file ./example.nix dhallPackages.true
The above package produces the following directory tree:
```bash
```ShellSession
$ tree -a ./result
result
├── .cache
@ -135,7 +135,7 @@ result
* `source.dhall` contains the result of interpreting our Dhall package:
```bash
```ShellSession
$ cat ./result/source.dhall
True
```
@ -143,7 +143,7 @@ result
* The `.cache` subdirectory contains one binary cache product encoding the
same result as `source.dhall`:
```bash
```ShellSession
$ dhall decode < ./result/.cache/dhall/122027abdeddfe8503496adeb623466caa47da5f63abd2bc6fa19f6cfcb73ecfed70
True
```
@ -151,7 +151,7 @@ result
* `binary.dhall` contains a Dhall expression which handles fetching and decoding
the same cache product:
```bash
```ShellSession
$ cat ./result/binary.dhall
missing sha256:27abdeddfe8503496adeb623466caa47da5f63abd2bc6fa19f6cfcb73ecfed70
$ cp -r ./result/.cache .cache
@ -168,7 +168,7 @@ to conserve disk space when they are used exclusively as dependencies. For
example, if we build the Prelude package it will only contain the binary
encoding of the expression:
```bash
```ShellSession
$ nix build --file ./example.nix dhallPackages.Prelude
$ tree -a result
@ -199,7 +199,7 @@ Dhall overlay like this:
… and now the Prelude will contain the fully decoded result of interpreting
the Prelude:
```bash
```ShellSession
$ nix build --file ./example.nix dhallPackages.Prelude
$ tree -a result
@ -302,7 +302,7 @@ Additionally, `buildDhallGitHubPackage` accepts the same arguments as
You can use the `dhall-to-nixpkgs` command-line utility to automate
packaging Dhall code. For example:
```bash
```ShellSession
$ nix-env --install --attr haskellPackages.dhall-nixpkgs
$ nix-env --install --attr nix-prefetch-git # Used by dhall-to-nixpkgs
@ -329,12 +329,12 @@ The utility takes care of automatically detecting remote imports and converting
them to package dependencies. You can also use the utility on local
Dhall directories, too:
```bash
```ShellSession
$ dhall-to-nixpkgs directory ~/proj/dhall-semver
{ buildDhallDirectoryPackage, Prelude }:
buildDhallDirectoryPackage {
name = "proj";
src = /Users/gabriel/proj/dhall-semver;
src = ~/proj/dhall-semver;
file = "package.dhall";
source = false;
document = false;
@ -342,6 +342,37 @@ $ dhall-to-nixpkgs directory ~/proj/dhall-semver
}
```
### Remote imports as fixed-output derivations {#ssec-dhall-remote-imports-as-fod}
`dhall-to-nixpkgs` has the ability to fetch and build remote imports as
fixed-output derivations by using their Dhall integrity check. This is
sometimes easier than manually packaging all remote imports.
This can be used like the following:
```ShellSession
$ dhall-to-nixpkgs directory --fixed-output-derivations ~/proj/dhall-semver
{ buildDhallDirectoryPackage, buildDhallUrl }:
buildDhallDirectoryPackage {
name = "proj";
src = ~/proj/dhall-semver;
file = "package.dhall";
source = false;
document = false;
dependencies = [
(buildDhallUrl {
url = "https://prelude.dhall-lang.org/v17.0.0/package.dhall";
hash = "sha256-ENs8kZwl6QRoM9+Jeo/+JwHcOQ+giT2VjDQwUkvlpD4=";
dhallHash = "sha256:10db3c919c25e9046833df897a8ffe2701dc390fa0893d958c3430524be5a43e";
})
];
}
```
Here, `dhall-semver`'s `Prelude` dependency is fetched and built with the
`buildDhallUrl` helper function, instead of being passed in as a function
argument.
## Overriding dependency versions {#ssec-dhall-overriding-dependency-versions}
Suppose that we change our `true.dhall` example expression to depend on an older
@ -359,7 +390,7 @@ in Prelude.Bool.not False
If we try to rebuild that expression the build will fail:
```
```ShellSession
$ nix build --file ./example.nix dhallPackages.true
builder for '/nix/store/0f1hla7ff1wiaqyk1r2ky4wnhnw114fi-true.drv' failed with exit code 1; last 10 log lines:
@ -385,7 +416,7 @@ importing the URL.
However, we can override the default Prelude version by using `dhall-to-nixpkgs`
to create a Dhall package for our desired Prelude:
```bash
```ShellSession
$ dhall-to-nixpkgs github https://github.com/dhall-lang/dhall-lang.git \
--name Prelude \
--directory Prelude \
@ -396,7 +427,7 @@ $ dhall-to-nixpkgs github https://github.com/dhall-lang/dhall-lang.git \
… and then referencing that package in our Dhall overlay, by either overriding
the Prelude globally for all packages, like this:
```bash
```nix
dhallOverrides = self: super: {
true = self.callPackage ./true.nix { };
@ -407,7 +438,7 @@ the Prelude globally for all packages, like this:
… or selectively overriding the Prelude dependency for just the `true` package,
like this:
```bash
```nix
dhallOverrides = self: super: {
true = self.callPackage ./true.nix {
Prelude = self.callPackage ./Prelude.nix { };

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@ -0,0 +1,96 @@
{ cacert, dhall, dhall-docs, haskell, lib, runCommand }:
# `buildDhallUrl` is similar to `buildDhallDirectoryPackage` or
# `buildDhallGitHubPackage`, but instead builds a Nixpkgs Dhall package
# based on a hashed URL. This will generally be a URL that has an integrity
# check in a Dhall file.
#
# Similar to `buildDhallDirectoryPackage` and `buildDhallGitHubPackage`, the output
# of this function is a derivation that has a `binary.dhall` file, along with
# a `.cache/` directory with the actual contents of the Dhall file from the
# suppiled URL.
#
# This function is primarily used by `dhall-to-nixpkgs directory --fixed-output-derivations`.
{ # URL of the input Dhall file.
# example: "https://raw.githubusercontent.com/cdepillabout/example-dhall-repo/c1b0d0327146648dcf8de997b2aa32758f2ed735/example1.dhall"
url
# Nix hash of the input Dhall file.
# example: "sha256-ZTSiQUXpPbPfPvS8OeK6dDQE6j6NbP27ho1cg9YfENI="
, hash
# Dhall hash of the input Dhall file.
# example: "sha256:6534a24145e93db3df3ef4bc39e2ba743404ea3e8d6cfdbb868d5c83d61f10d2"
, dhallHash
# Name for this derivation.
, name ? (baseNameOf url + "-cache")
# `buildDhallUrl` can include both a "source distribution" in
# `source.dhall` and a "binary distribution" in `binary.dhall`:
#
# * `source.dhall` is a dependency-free αβ-normalized Dhall expression
#
# * `binary.dhall` is an expression of the form: `missing sha256:${HASH}`
#
# This expression requires you to install the cache product located at
# `.cache/dhall/1220${HASH}` to successfully resolve
#
# By default, `buildDhallUrl` only includes "binary.dhall" to conserve
# space within the Nix store, but if you set the following `source` option to
# `true` then the package will also include `source.dhall`.
, source ? false
}:
let
# HTTP support is disabled in order to force that HTTP dependencies are built
# using Nix instead of using Dhall's support for HTTP imports.
dhallNoHTTP = haskell.lib.appendConfigureFlag dhall "-f-with-http";
# This uses Dhall's remote importing capabilities for downloading a Dhall file.
# The output Dhall file has all imports resolved, and then is
# alpha-normalized and binary-encoded.
downloadedEncodedFile =
runCommand
(baseNameOf url)
{
outputHashAlgo = null;
outputHash = hash;
name = baseNameOf url;
nativeBuildInputs = [ cacert ];
}
''
echo "${url} ${dhallHash}" > in-dhall-file
${dhall}/bin/dhall --alpha --plain --file in-dhall-file | ${dhallNoHTTP}/bin/dhall encode > $out
'';
cache = ".cache";
data = ".local/share";
cacheDhall = "${cache}/dhall";
dataDhall = "${data}/dhall";
sourceFile = "source.dhall";
in
runCommand name { } (''
set -eu
mkdir -p ${cacheDhall} $out/${cacheDhall}
export XDG_CACHE_HOME=$PWD/${cache}
SHA_HASH="${dhallHash}"
HASH_FILE="''${SHA_HASH/sha256:/1220}"
cp ${downloadedEncodedFile} $out/${cacheDhall}/$HASH_FILE
echo "missing $SHA_HASH" > $out/binary.dhall
'' +
lib.optionalString source ''
${dhallNoHTTP}/bin/dhall decode --file ${downloadedEncodedFile} > $out/${sourceFile}
'')

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@ -58,4 +58,6 @@ with pkgs;
};
writers = callPackage ../build-support/writers/test.nix {};
dhall = callPackage ./dhall { };
}

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@ -0,0 +1,14 @@
{ dhallPackages, lib }:
# This file tests that dhallPackages.buildDhallUrl is able to successfully
# build a Nix Dhall package for a given remote Dhall import.
#
# TODO: It would be nice to extend this test to make sure that the resulting
# Nix Dhall package is has the expected contents.
dhallPackages.buildDhallUrl {
url = "https://raw.githubusercontent.com/cdepillabout/example-dhall-nix/e6a675c72ecd4dd23d254a02aea8181fe875747f/mydhallfile.dhall";
hash = "sha256-434x+QjHRzuprBdw0h6wmwB1Zj6yZqQb533me8XdO4c=";
dhallHash = "sha256:e37e31f908c7473ba9ac1770d21eb09b0075663eb266a41be77de67bc5dd3b87";
source = true;
}

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@ -0,0 +1,5 @@
{ lib, callPackage }:
lib.recurseIntoAttrs {
buildDhallUrl = callPackage ./buildDhallUrl { };
}

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@ -17,12 +17,16 @@ let
buildDhallDirectoryPackage =
callPackage ../development/interpreters/dhall/build-dhall-directory-package.nix { };
buildDhallUrl =
callPackage ../development/interpreters/dhall/build-dhall-url.nix { };
in
{ inherit
callPackage
buildDhallPackage
buildDhallGitHubPackage
buildDhallDirectoryPackage
buildDhallUrl
;
lib = import ../development/dhall-modules/lib.nix { inherit lib; };