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records: 'match-record' checks fields at macro-expansion time.

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This allows 'match-record' to be more efficient (field offsets are
computed at compilation time) and to report unknown fields at
macro-expansion time.

* guix/records.scm (map-fields): New macro.
(define-record-type*)[rtd-identifier]: New procedure.
Define TYPE as a macro and use a separate identifier for the RTD.
(lookup-field, match-record-inner): New macros.
(match-record): Rewrite in terms of 'match-error-inner'.
* tests/records.scm ("match-record, simple")
("match-record, unknown field"): New tests.
* gnu/services/cuirass.scm (cuirass-shepherd-service): Rename 'log-file'
local variable to 'main-log-file'.
* gnu/services/getmail.scm (serialize-getmail-configuration-file): Move
after <getmail-configuration-file> definition.
This commit is contained in:
Ludovic Courtès 2022-11-19 17:23:04 +01:00
parent a420b4f34e
commit 754a7660a1
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GPG key ID: 090B11993D9AEBB5
4 changed files with 122 additions and 24 deletions
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4
gnu/services/cuirass.scm
View file

@ -125,7 +125,7 @@ (define (cuirass-shepherd-service config)
(let ((cuirass (cuirass-configuration-cuirass config))
(cache-directory (cuirass-configuration-cache-directory config))
(web-log-file (cuirass-configuration-web-log-file config))
(log-file (cuirass-configuration-log-file config))
(main-log-file (cuirass-configuration-log-file config))
(user (cuirass-configuration-user config))
(group (cuirass-configuration-group config))
(interval (cuirass-configuration-interval config))
@ -169,7 +169,7 @@ (define (cuirass-shepherd-service config)
#:user #$user
#:group #$group
#:log-file #$log-file))
#:log-file #$main-log-file))
(stop #~(make-kill-destructor)))
,(shepherd-service
(documentation "Run Cuirass web interface.")

22
gnu/services/getmail.scm
View file

@ -215,17 +215,6 @@ (define-configuration getmail-options-configuration
(parameter-alist '())
"Extra options to include."))
(define (serialize-getmail-configuration-file field-name val)
(match-record val <getmail-configuration-file>
(retriever destination options)
#~(string-append
"[retriever]\n"
#$(serialize-getmail-retriever-configuration #f retriever)
"\n[destination]\n"
#$(serialize-getmail-destination-configuration #f destination)
"\n[options]\n"
#$(serialize-getmail-options-configuration #f options))))
(define-configuration getmail-configuration-file
(retriever
(getmail-retriever-configuration (getmail-retriever-configuration))
@ -237,6 +226,17 @@ (define-configuration getmail-configuration-file
(getmail-options-configuration (getmail-options-configuration))
"Configure getmail."))
(define (serialize-getmail-configuration-file field-name val)
(match-record val <getmail-configuration-file>
(retriever destination options)
#~(string-append
"[retriever]\n"
#$(serialize-getmail-retriever-configuration #f retriever)
"\n[destination]\n"
#$(serialize-getmail-destination-configuration #f destination)
"\n[options]\n"
#$(serialize-getmail-options-configuration #f options))))
(define (serialize-symbol field-name val) "")
(define (serialize-getmail-configuration field-name val) "")

87
guix/records.scm
View file

@ -1,5 +1,5 @@
;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020, 2021 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2012-2022 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2018 Mark H Weaver <mhw@netris.org>
;;;
;;; This file is part of GNU Guix.
@ -104,6 +104,10 @@ (define (report-duplicate-field-specifier name ctor)
(()
#t)))))))
(define-syntax map-fields
(lambda (x)
(syntax-violation 'map-fields "bad use of syntactic keyword" x x)))
(define-syntax-parameter this-record
(lambda (s)
"Return the record being defined. This macro may only be used in the
@ -325,6 +329,15 @@ (define-record-type* <thing> thing make-thing
field and its 'loc' field---the latter is marked as \"innate\", so it is not
inherited."
(define (rtd-identifier type)
;; Return an identifier derived from TYPE to name its record type
;; descriptor (RTD).
(let ((type-name (syntax->datum type)))
(datum->syntax
type
(string->symbol
(string-append "% " (symbol->string type-name) " rtd")))))
(define (field-default-value s)
(syntax-case s (default)
((field (default val) _ ...)
@ -428,10 +441,31 @@ (define (compute-abi-cookie field-specs)
field)))
field-spec)))
#`(begin
(define-record-type type
(define-record-type #,(rtd-identifier #'type)
(ctor field ...)
pred
field-spec* ...)
;; Rectify the vtable type name...
(set-struct-vtable-name! #,(rtd-identifier #'type) 'type)
(cond-expand
(guile-3
;; ... and the record type name.
(struct-set! #,(rtd-identifier #'type) vtable-offset-user
'type))
(else #f))
(define-syntax type
(lambda (s)
"This macro lets us query record type info at
macro-expansion time."
(syntax-case s (map-fields)
((_ map-fields macro)
#'(macro (field ...)))
(id
(identifier? #'id)
#'#,(rtd-identifier #'type)))))
(define #,(current-abi-identifier #'type)
#,cookie)
@ -535,19 +569,50 @@ (define (recutils->alist port)
(else
(error "unmatched line" line))))))))
;;;
;;; Pattern matching.
;;;
(define-syntax lookup-field
(lambda (s)
"Look up FIELD in the given list and return an expression that represents
its offset in the record. Raise a syntax violation when the field is not
found."
(syntax-case s ()
((_ field offset ())
(syntax-violation 'lookup-field "unknown record type field"
s #'field))
((_ field offset (head tail ...))
(free-identifier=? #'field #'head)
#'offset)
((_ field offset (_ tail ...))
#'(lookup-field field (+ 1 offset) (tail ...))))))
(define-syntax match-record-inner
(lambda (s)
(syntax-case s ()
((_ record type (field rest ...) body ...)
#`(let-syntax ((field-offset (syntax-rules ()
((_ f)
(lookup-field field 0 f)))))
(let* ((offset (type map-fields field-offset))
(field (struct-ref record offset)))
(match-record-inner record type (rest ...) body ...))))
((_ record type () body ...)
#'(begin body ...)))))
(define-syntax match-record
(syntax-rules ()
"Bind each FIELD of a RECORD of the given TYPE to it's FIELD name.
The order in which fields appear does not matter. A syntax error is raised if
an unknown field is queried.
The current implementation does not support thunked and delayed fields."
((_ record type (field fields ...) body ...)
;; TODO support thunked and delayed fields
((_ record type (fields ...) body ...)
(if (eq? (struct-vtable record) type)
;; TODO compute indices and report wrong-field-name errors at
;; expansion time
;; TODO support thunked and delayed fields
(let ((field ((record-accessor type 'field) record)))
(match-record record type (fields ...) body ...))
(throw 'wrong-type-arg record)))
((_ record type () body ...)
(begin body ...))))
(match-record-inner record type (fields ...) body ...)
(throw 'wrong-type-arg record)))))
;;; records.scm ends here

33
tests/records.scm
View file

@ -528,4 +528,37 @@ (define (make-me-a-record) (foo)))
'("a" "b" "c")
'("a")))
(test-equal "match-record, simple"
'((1 2) (a b))
(let ()
(define-record-type* <foo> foo make-foo
foo?
(first foo-first (default 1))
(second foo-second))
(list (match-record (foo (second 2)) <foo>
(first second)
(list first second))
(match-record (foo (first 'a) (second 'b)) <foo>
(second first)
(list first second)))))
(test-equal "match-record, unknown field"
'syntax-error
(catch 'syntax-error
(lambda ()
(eval '(begin
(use-modules (guix records))
(define-record-type* <foo> foo make-foo
foo?
(first foo-first (default 1))
(second foo-second))
(match-record (foo (second 2)) <foo>
(one two)
#f))
(make-fresh-user-module)))
(lambda (key . args) key)))
(test-end)