;; 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 format)
(chicken irregex)
(chicken port)
(chicken file)
(chicken file posix)
(chicken process)
(chicken process-context)
(chicken string)
(matchable)
(only (chicken io) read-string))
(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
path - print source folder for the target
repl - start a nix repl in the repository root
run - build a target and execute its output
file all feedback on b.tvl.fyi
USAGE
)
;; parse target definitions. trailing slashes on physical targets are
;; allowed for shell autocompletion.
;;
;; component ::= any string without "/" or ":"
;;
;; physical-target ::= <component>
;; | <component> "/"
;; | <component> "/" <physical-target>
;;
;; virtual-target ::= ":" <component>
;;
;; relative-target ::= <physical-target>
;; | <virtual-target>
;; | <physical-target> <virtual-target>
;;
;; root-anchor ::= "//"
;;
;; target ::= <relative-target> | <root-anchor> <relative-target>
;; read a path component until it looks like something else is coming
(define (read-component first port)
(let ((keep-reading?
(lambda () (not (or (eq? #\/ (peek-char port))
(eq? #\: (peek-char port))
(eof-object? (peek-char port)))))))
(let reader ((acc (list first))
(condition (keep-reading?)))
(if condition (reader (cons (read-char port) acc) (keep-reading?))
(list->string (reverse acc))))))
;; read something that started with a slash. what will it be?
(define (read-slash port)
(if (eq? #\/ (peek-char port))
(begin (read-char port)
'root-anchor)
'path-separator))
;; read any target token and leave port sitting at the next one
(define (read-token port)
(match (read-char port)
[#\/ (read-slash port)]
[#\: 'virtual-separator]
[other (read-component other port)]))
;; read a target into a list of target tokens
(define (read-target target-str)
(call-with-input-string
target-str
(lambda (port)
(let reader ((acc '()))
(if (eof-object? (peek-char port))
(reverse acc)
(reader (cons (read-token port) acc)))))))
(define-record target absolute components virtual)
(define (empty-target) (make-target #f '() #f))
(define-record-printer (target t out)
(fprintf out (conc (if (target-absolute t) "//" "")
(string-intersperse (target-components t) "/")
(if (target-virtual t) ":" "")
(or (target-virtual t) ""))))
;; parse and validate a list of target tokens
(define parse-tokens
(lambda (tokens #!optional (mode 'root) (acc (empty-target)))
(match (cons mode tokens)
;; absolute target
[('root . ('root-anchor . rest))
(begin (target-absolute-set! acc #t)
(parse-tokens rest 'root acc))]
;; relative target minus potential garbage
[('root . (not ('path-separator . _)))
(parse-tokens tokens 'normal acc)]
;; virtual target
[('normal . ('virtual-separator . rest))
(parse-tokens rest 'virtual acc)]
[('virtual . ((? string? v)))
(begin
(target-virtual-set! acc v)
acc)]
;; chomp through all components and separators
[('normal . ('path-separator . rest)) (parse-tokens rest 'normal acc)]
[('normal . ((? string? component) . rest))
(begin (target-components-set!
acc (append (target-components acc) (list component)))
(parse-tokens rest 'normal acc ))]
;; nothing more to parse and not in a weird state, all done, yay!
[('normal . ()) acc]
;; oh no, we ran out of input too early :(
[(_ . ()) `(error . ,(format "unexpected end of input while parsing ~s target" mode))]
;; something else was invalid :(
[_ `(error . ,(format "unexpected ~s while parsing ~s target" (car tokens) mode))])))
(define (parse-target target)
(parse-tokens (read-target target)))
;; turn relative targets into absolute targets based on the current
;; directory
(define (normalise-target t)
(when (not (target-absolute t))
(target-components-set! t (append (relative-repo-path)
(target-components t)))
(target-absolute-set! t #t))
t)
;; nix doesn't care about the distinction between physical and virtual
;; targets, normalise it away
(define (normalised-components t)
(if (target-virtual t)
(append (target-components t) (list (target-virtual t)))
(target-components t)))
;; 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
(or (get-environment-variable "MG_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
;;
;; an empty target will build the current folder instead.
;;
;; this uses builtins.getAttr explicitly to avoid problems with
;; escaping.
(define (nix-expr-for target)
(let nest ((parts (normalised-components (normalise-target target)))
(acc (conc "(import " (repository-root) " {})")))
(match parts
[() (conc "with builtins; " acc)]
[_ (nest (cdr parts)
(conc "(getAttr \""
(nix-escape (car parts))
"\" " acc ")"))])))
;; exit and complain at the user if something went wrong
(define (mg-error message)
(format (current-error-port) "[mg] error: ~A~%" message)
(exit 1))
(define (guarantee-success value)
(match value
[('error . message) (mg-error message)]
[_ value]))
(define-record build-args target passthru unknown)
(define (execute-build args)
(let ((expr (nix-expr-for (build-args-target args))))
(fprintf (current-error-port) "[mg] building target ~A~%" (build-args-target args))
(process-execute "nix-build" (append (list "-E" expr "--show-trace")
(or (build-args-passthru args) '())))))
;; split the arguments used for builds into target/unknown args/nix
;; args, where the latter occur after '--'
(define (parse-build-args acc args)
(match args
;; no arguments remaining, return accumulator as is
[() acc]
;; next argument is '--' separator, split off passthru and
;; return
[("--" . passthru)
(begin
(build-args-passthru-set! acc passthru)
acc)]
[(arg . rest)
;; set target if not already known (and if the first
;; argument does not look like an accidental unknown
;; parameter)
(if (and (not (build-args-target acc))
(not (substring=? "-" arg)))
(begin
(build-args-target-set! acc (guarantee-success (parse-target arg)))
(parse-build-args acc rest))
;; otherwise, collect unknown arguments
(begin
(build-args-unknown-set! acc (append (or (build-args-unknown acc) '())
(list arg)))
(parse-build-args acc rest)))]))
;; parse the passed build args, applying sanity checks and defaulting
;; the target if necessary, then execute the build
(define (build args)
(let ((parsed (parse-build-args (make-build-args #f #f #f) args)))
;; fail if there are unknown arguments present
(when (build-args-unknown parsed)
(let ((unknown (string-intersperse (build-args-unknown parsed))))
(mg-error (sprintf "unknown arguments: ~a
if you meant to pass these arguments to nix, please separate them with
'--' like so:
mg build ~a -- ~a"
unknown
(or (build-args-target parsed) "")
unknown))))
;; default the target to the current folder's main target
(unless (build-args-target parsed)
(build-args-target-set! parsed (empty-target)))
(execute-build parsed)))
(define (execute-shell t)
(let ((expr (nix-expr-for t))
(user-shell (or (get-environment-variable "SHELL") "bash")))
(fprintf (current-error-port) "[mg] entering shell for ~A~%" t)
(process-execute "nix-shell"
(list "-E" expr "--command" user-shell))))
(define (shell args)
(match args
[() (execute-shell (empty-target))]
[(arg) (execute-shell
(guarantee-success (parse-target arg)))]
[other (print "not yet implemented")]))
(define (repl args)
(process-execute "nix" (append (list "repl" "--show-trace" (repository-root)) args)))
(define (execute-run t #!optional cmd-args)
(fprintf (current-error-port) "[mg] building target ~A~%" t)
(let* ((expr (nix-expr-for t))
(out (call-with-input-pipe
(apply string-append
;; TODO(sterni): temporary gc root
(intersperse `("nix-build" "-E" ,(qs expr) "--no-out-link")
" "))
(lambda (p)
(string-chomp (let ((s (read-string #f p)))
(if (eq? s #!eof) "" s)))))))
;; TODO(sterni): can we get the exit code of nix-build somehow?
(when (= (string-length out) 0)
(mg-error (string-append "Couldn't build target " (format "~A" t)))
(exit 1))
(fprintf (current-error-port) "[mg] running target ~A~%" t)
(process-execute
;; If the output is a file, we assume it's an executable à la writeExecline,
;; otherwise we look in the bin subdirectory and pick the only executable.
;; Handling multiple executables is not possible at the moment, the choice
;; could be made via a command line flag in the future.
(if (regular-file? out)
out
(let* ((dir-path (string-append out "/bin"))
(dir-contents (if (directory-exists? dir-path)
(directory dir-path #f)
'())))
(case (length dir-contents)
((0) (mg-error "no executables in build output")
(exit 1))
((1) (string-append dir-path "/" (car dir-contents)))
(else (mg-error "more than one executable in build output")
(exit 1)))))
cmd-args)))
(define (run args)
(match args
[() (execute-run (empty-target))]
;; TODO(sterni): flag for selecting binary name
[other (execute-run (guarantee-success (parse-target (car args)))
(cdr args))]))
(define (path args)
(match args
[(arg)
(print (apply string-append
(intersperse
(cons (repository-root)
(target-components
(normalise-target
(guarantee-success (parse-target arg)))))
"/")))]
[() (mg-error "path command needs a target")]
[other (mg-error (format "unknown arguments: ~a" other))]))
(define (main args)
(match args
[() (print usage)]
[("build" . _) (build (cdr args))]
[("shell" . _) (shell (cdr args))]
[("path" . _) (path (cdr args))]
[("repl" . _) (repl (cdr args))]
[("run" . _) (run (cdr args))]
[other (begin (print "unknown command: mg " args)
(print usage))]))
(main (command-line-arguments))
