feat(tools/magrathea): bootstrap a tool for working with depot

this is going to be a serious version of //tools/depot-build.

right now it doesn't support parsing any target specs yet, so only
shells and builds for the physical project of the current folder work.

Change-Id: I4308e29da940571622ff9e539fbb8ededd27aca7
Reviewed-on: https://cl.tvl.fyi/c/depot/+/4335
Tested-by: BuildkiteCI
Reviewed-by: tazjin <mail@tazj.in>
Reviewed-by: grfn <grfn@gws.fyi>
This commit is contained in:
Vincent Ambo 2021-12-15 19:31:47 +03:00 committed by tazjin
parent 887ac4d3d4
commit 564ad52b30
4 changed files with 137 additions and 0 deletions

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@ -37,6 +37,9 @@ case "${TARGET_TOOL}" in
meson)
attr="third_party.nixpkgs.meson"
;;
mg)
attr="tools.magrathea"
;;
ninja)
attr="third_party.nixpkgs.ninja"
;;

1
bin/mg Symbolic link
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@ -0,0 +1 @@
__dispatch.sh

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@ -0,0 +1,23 @@
# magrathea helps you build planets
#
# it is a tool for working with monorepos in the style of tvl's depot
{ pkgs, ... }:
pkgs.stdenv.mkDerivation {
name = "magrathea";
src = ./.;
dontInstall = true;
nativeBuildInputs = [ pkgs.chicken ];
buildInputs = with pkgs.chickenPackages.chickenEggs; [
matchable
srfi-13
];
propagatedBuildInputs = [ pkgs.git ];
buildPhase = ''
mkdir -p $out/bin
csc -o $out/bin/mg -static ${./mg.scm}
'';
}

110
tools/magrathea/mg.scm Normal file
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@ -0,0 +1,110 @@
;; magrathea helps you build planets
;;
;; it is a tiny tool designed to ease workflows in monorepos that are
;; modeled after the tvl depot.
;;
;; users familiar with workflows from other, larger monorepos may be
;; used to having a build tool that can work in any tree location.
;; magrathea enables this, but with nix-y monorepos.
(import (chicken base)
(chicken io)
(chicken irregex)
(chicken process)
(chicken process-context)
(chicken string)
(matchable))
(define usage #<<USAGE
usage: mg <command> [<target>]
target:
a target specification with meaning inside of the repository. can
be absolute (starting with //) or relative to the current directory
(as long as said directory is inside of the repo). if no target is
specified, the current directory's physical target is built.
for example:
//tools/magrathea - absolute physical target
//foo/bar:baz - absolute virtual target
magrathea - relative physical target
:baz - relative virtual target
commands:
build - build a target
shell - enter a shell with the target's build dependencies
file all feedback on b.tvl.fyi
USAGE
)
;; return the current repository root as a string
(define mg--repository-root #f)
(define (repository-root)
(or mg--repository-root
(begin
(set! mg--repository-root
(string-chomp
(call-with-input-pipe "git rev-parse --show-toplevel"
(lambda (p) (read-string #f p)))))
mg--repository-root)))
;; determine the current path relative to the root of the repository
;; and return it as a list of path components.
(define (relative-repo-path)
(string-split
(substring (current-directory) (string-length (repository-root))) "/"))
;; escape a string for interpolation in nix code
(define (nix-escape str)
(string-translate* str '(("\"" . "\\\"")
("${" . "\\${"))))
;; create a nix expression to build the attribute at the specified
;; components
;;
;; this uses builtins.getAttr explicitly to avoid problems with
;; escaping.
(define nix-expr-for
(lambda (parts #!optional (acc (conc "(import " (repository-root) " {})")))
(match parts
[() (conc "with builtins; " acc)]
[_ (nix-expr-for (cdr parts)
(conc "(getAttr \"" (nix-escape (car parts)) "\" " acc ")"))])))
(define (execute-build components)
(let ((attr (string-intersperse components "."))
(expr (nix-expr-for components)))
(print "[mg] building attribute '" attr "'")
(process-execute "nix-build" (list "-E" expr "--show-trace"))))
(define (build args)
(match args
;; simplest case: plain mg build with no target spec -> build
;; the current folder's main target.
[() (execute-build (relative-repo-path))]
[other (print "not yet implemented")]))
(define (execute-shell components)
(let ((attr (string-intersperse components "."))
(expr (nix-expr-for components))
(user-shell (or (get-environment-variable "SHELL") "bash")))
(print "[mg] entering shell for '" attr "'")
(process-execute "nix-shell"
(list "-E" expr "--command" user-shell))))
(define (shell args)
(match args
[() (execute-shell (relative-repo-path))]
[other (print "not yet implemented")]))
(define (main args)
(match args
[() (print usage)]
[("build" ...) (build (cdr args))]
[("shell" ...) (shell (cdr args))]
[other (begin (print "unknown command: mg " args)
(print usage))]))
(main (command-line-arguments))