1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
|
# Agda {#agda}
## How to use Agda
Agda is available as the [agda](https://search.nixos.org/packages?channel=unstable&show=agda&from=0&size=30&sort=relevance&query=agda)
package.
The `agda` package installs an Agda-wrapper, which calls `agda` with `--library-file`
set to a generated library-file within the nix store, this means your library-file in
`$HOME/.agda/libraries` will be ignored. By default the agda package installs Agda
with no libraries, i.e. the generated library-file is empty. To use Agda with libraries,
the `agda.withPackages` function can be used. This function either takes:
* A list of packages,
* or a function which returns a list of packages when given the `agdaPackages` attribute set,
* or an attribute set containing a list of packages and a GHC derivation for compilation (see below).
* or an attribute set containing a function which returns a list of packages when given the `agdaPackages` attribute set and a GHC derivation for compilation (see below).
For example, suppose we wanted a version of Agda which has access to the standard library. This can be obtained with the expressions:
```nix
agda.withPackages [ agdaPackages.standard-library ]
```
or
```nix
agda.withPackages (p: [ p.standard-library ])
```
or can be called as in the [Compiling Agda](#compiling-agda) section.
If you want to use a different version of a library (for instance a development version)
override the `src` attribute of the package to point to your local repository
```nix
agda.withPackages (p: [
(p.standard-library.overrideAttrs (oldAttrs: {
version = "local version";
src = /path/to/local/repo/agda-stdlib;
}))
])
```
You can also reference a GitHub repository
```nix
agda.withPackages (p: [
(p.standard-library.overrideAttrs (oldAttrs: {
version = "1.5";
src = fetchFromGitHub {
repo = "agda-stdlib";
owner = "agda";
rev = "v1.5";
sha256 = "16fcb7ssj6kj687a042afaa2gq48rc8abihpm14k684ncihb2k4w";
};
}))
])
```
If you want to use a library not added to Nixpkgs, you can add a
dependency to a local library by calling `agdaPackages.mkDerivation`.
```nix
agda.withPackages (p: [
(p.mkDerivation {
pname = "your-agda-lib";
version = "1.0.0";
src = /path/to/your-agda-lib;
})
])
```
Again you can reference GitHub
```nix
agda.withPackages (p: [
(p.mkDerivation {
pname = "your-agda-lib";
version = "1.0.0";
src = fetchFromGitHub {
repo = "repo";
owner = "owner";
version = "...";
rev = "...";
sha256 = "...";
};
})
])
```
See [Building Agda Packages](#building-agda-packages) for more information on `mkDerivation`.
Agda will not by default use these libraries. To tell Agda to use a library we have some options:
* Call `agda` with the library flag:
```ShellSession
$ agda -l standard-library -i . MyFile.agda
```
* Write a `my-library.agda-lib` file for the project you are working on which may look like:
```
name: my-library
include: .
depend: standard-library
```
* Create the file `~/.agda/defaults` and add any libraries you want to use by default.
More information can be found in the [official Agda documentation on library management](https://agda.readthedocs.io/en/v2.6.1/tools/package-system.html).
## Compiling Agda
Agda modules can be compiled using the GHC backend with the `--compile` flag. A version of `ghc` with `ieee754` is made available to the Agda program via the `--with-compiler` flag.
This can be overridden by a different version of `ghc` as follows:
```nix
agda.withPackages {
pkgs = [ ... ];
ghc = haskell.compiler.ghcHEAD;
}
```
## Writing Agda packages
To write a nix derivation for an Agda library, first check that the library has a `*.agda-lib` file.
A derivation can then be written using `agdaPackages.mkDerivation`. This has similar arguments to `stdenv.mkDerivation` with the following additions:
* `everythingFile` can be used to specify the location of the `Everything.agda` file, defaulting to `./Everything.agda`. If this file does not exist then either it should be patched in or the `buildPhase` should be overridden (see below).
* `libraryName` should be the name that appears in the `*.agda-lib` file, defaulting to `pname`.
* `libraryFile` should be the file name of the `*.agda-lib` file, defaulting to `${libraryName}.agda-lib`.
Here is an example `default.nix`
```nix
{ nixpkgs ? <nixpkgs> }:
with (import nixpkgs {});
agdaPackages.mkDerivation {
version = "1.0";
pname = "my-agda-lib";
src = ./.;
buildInputs = [
agdaPackages.standard-library
];
}
```
### Building Agda packages
The default build phase for `agdaPackages.mkDerivation` simply runs `agda` on the `Everything.agda` file.
If something else is needed to build the package (e.g. `make`) then the `buildPhase` should be overridden.
Additionally, a `preBuild` or `configurePhase` can be used if there are steps that need to be done prior to checking the `Everything.agda` file.
`agda` and the Agda libraries contained in `buildInputs` are made available during the build phase.
### Installing Agda packages
The default install phase copies Agda source files, Agda interface files (`*.agdai`) and `*.agda-lib` files to the output directory.
This can be overridden.
By default, Agda sources are files ending on `.agda`, or literate Agda files ending on `.lagda`, `.lagda.tex`, `.lagda.org`, `.lagda.md`, `.lagda.rst`. The list of recognised Agda source extensions can be extended by setting the `extraExtensions` config variable.
## Adding Agda packages to Nixpkgs
To add an Agda package to `nixpkgs`, the derivation should be written to `pkgs/development/libraries/agda/${library-name}/` and an entry should be added to `pkgs/top-level/agda-packages.nix`. Here it is called in a scope with access to all other Agda libraries, so the top line of the `default.nix` can look like:
```nix
{ mkDerivation, standard-library, fetchFromGitHub }:
```
Note that the derivation function is called with `mkDerivation` set to `agdaPackages.mkDerivation`, therefore you
could use a similar set as in your `default.nix` from [Writing Agda Packages](#writing-agda-packages) with
`agdaPackages.mkDerivation` replaced with `mkDerivation`.
Here is an example skeleton derivation for iowa-stdlib:
```nix
mkDerivation {
version = "1.5.0";
pname = "iowa-stdlib";
src = ...
libraryFile = "";
libraryName = "IAL-1.3";
buildPhase = ''
patchShebangs find-deps.sh
make
'';
}
```
This library has a file called `.agda-lib`, and so we give an empty string to `libraryFile` as nothing precedes `.agda-lib` in the filename. This file contains `name: IAL-1.3`, and so we let `libraryName = "IAL-1.3"`. This library does not use an `Everything.agda` file and instead has a Makefile, so there is no need to set `everythingFile` and we set a custom `buildPhase`.
When writing an Agda package it is essential to make sure that no `.agda-lib` file gets added to the store as a single file (for example by using `writeText`). This causes Agda to think that the nix store is a Agda library and it will attempt to write to it whenever it typechecks something. See [https://github.com/agda/agda/issues/4613](https://github.com/agda/agda/issues/4613).
|