;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2010-2024 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2015 Alex Kost <alezost@gmail.com>
;;; Copyright © 2019, 2022-2024 Ricardo Wurmus <rekado@elephly.net>
;;; Copyright © 2021 Sarah Morgensen <iskarian@mgsn.dev>
;;; Copyright © 2021, 2022 Maxime Devos <maximedevos@telenet.be>
;;; Copyright © 2022 Hartmut Goebel <h.goebel@crazy-compilers.com>
;;;
;;; This file is part of GNU Guix.
;;;
;;; GNU Guix is free software; you can redistribute it and/or modify it
;;; under the terms of the GNU General Public License as published by
;;; the Free Software Foundation; either version 3 of the License, or (at
;;; your option) any later version.
;;;
;;; GNU Guix is distributed in the hope that it will be useful, but
;;; WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;;; GNU General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.

(define-module (guix upstream)
  #:use-module (guix records)
  #:use-module (guix utils)
  #:use-module (guix discovery)
  #:use-module ((guix download)
                #:select (download-to-store url-fetch))
  #:use-module (guix git-download)
  #:use-module (guix svn-download)
  #:use-module (guix gnupg)
  #:use-module (guix packages)
  #:use-module (guix diagnostics)
  #:use-module (guix ui)
  #:use-module (guix base32)
  #:use-module (guix gexp)
  #:autoload   (guix git) (latest-repository-commit git-reference->git-checkout)
  #:use-module (guix hash)
  #:use-module (guix store)
  #:use-module ((guix derivations) #:select (built-derivations derivation->output-path))
  #:autoload   (guix read-print) (object->string*)
  #:autoload   (gcrypt hash) (port-sha256)
  #:use-module (guix monads)
  #:use-module (srfi srfi-1)
  #:use-module (srfi srfi-9)
  #:use-module (srfi srfi-26)
  #:use-module (srfi srfi-34)
  #:use-module (srfi srfi-35)
  #:use-module (srfi srfi-71)
  #:use-module (rnrs bytevectors)
  #:use-module (ice-9 match)
  #:use-module (ice-9 regex)
  #:export (upstream-source
            upstream-source?
            upstream-source-package
            upstream-source-version
            upstream-source-urls
            upstream-source-signature-urls
            upstream-source-archive-types
            upstream-source-inputs

            upstream-input-type-predicate
            upstream-source-regular-inputs
            upstream-source-native-inputs
            upstream-source-propagated-inputs

            upstream-input
            upstream-input?
            upstream-input-name
            upstream-input-downstream-name
            upstream-input-type
            upstream-input-min-version
            upstream-input-max-version

            url-predicate
            url-prefix-predicate
            coalesce-sources

            upstream-updater
            upstream-updater?
            upstream-updater-name
            upstream-updater-description
            upstream-updater-predicate
            upstream-updater-import

            %updaters
            lookup-updater

            download-tarball
            package-archive-type
            package-latest-release
            package-latest-release*
            package-update
            update-package-source))

;;; Commentary:
;;;
;;; This module provides tools to represent and manipulate a upstream source
;;; code, and to auto-update package recipes.
;;;
;;; Code:

;; Representation of upstream's source.  There can be several URLs--e.g.,
;; tar.gz, tar.gz, etc.  There can be correspond signature URLs, one per
;; source URL.
(define-record-type* <upstream-source>
  upstream-source make-upstream-source
  upstream-source?
  (package        upstream-source-package)        ;string
  (version        upstream-source-version)        ;string
  (urls           upstream-source-urls) ;list of strings|git-references...
  (signature-urls upstream-source-signature-urls  ;#f | list of strings
                  (default #f))
  (inputs         upstream-source-inputs        ;#f | list of <upstream-input>
                  (delayed) (default #f))) ;delayed because optional and costly

;; Representation of a dependency as expressed by upstream.
(define-record-type* <upstream-input>
  upstream-input make-upstream-input
  upstream-input?
  (name         upstream-input-name)               ;upstream package name
  (downstream-name upstream-input-downstream-name) ;Guix package name
  (type         upstream-input-type          ;'regular | 'native | 'propagated
                (default 'regular))
  (min-version  upstream-input-min-version
                (default 'any))
  (max-version  upstream-input-max-version
                (default 'any)))

(define (upstream-input-type-predicate type)
  "Return a predicate that returns true when passed an <upstream-input> record
of the given TYPE (a symbol such as 'propagated)."
  (lambda (source)
    (eq? type (upstream-input-type source))))

(define (input-type-filter type)
  "Return a procedure that, given an <upstream-source>, returns the subset of
its inputs that have the given TYPE (a symbol such as 'native)."
  (lambda (source)
    "Return the subset of inputs of SOURCE that have the given TYPE."
    (filter (lambda (input)
              (eq? type (upstream-input-type input)))
            (upstream-source-inputs source))))

(define upstream-source-regular-inputs (input-type-filter 'regular))
(define upstream-source-native-inputs (input-type-filter 'native))
(define upstream-source-propagated-inputs (input-type-filter 'propagated))

(define* (url-predicate matching-url?)
  "Return a predicate that returns true when passed a package whose source is
an <origin> with the URL-FETCH method, and one of its URLs passes
MATCHING-URL?."
  (lambda (package)
    (match (package-source package)
      ((? origin? origin)
       (and (eq? (origin-method origin) url-fetch)
            (match (origin-uri origin)
              ((? string? url)
               (matching-url? url))
              (((? string? urls) ...)
               (any matching-url? urls))
              (_
               #f))))
      (_ #f))))

(define (url-prefix-predicate prefix)
  "Return a predicate that returns true when passed a package where one of its
source URLs starts with PREFIX."
  (url-predicate (cut string-prefix? prefix <>)))

(define (upstream-source-archive-types release)
  "Return the available types of archives for RELEASE---a list of strings such
as \"gz\" or \"xz\"."
  (map file-extension (upstream-source-urls release)))

(define (coalesce-sources sources)
  "Coalesce the elements of SOURCES, a list of <upstream-source>, that
correspond to the same version."
  (define (same-version? r1 r2)
    (string=? (upstream-source-version r1) (upstream-source-version r2)))

  (define (release>? r1 r2)
    (version>? (upstream-source-version r1) (upstream-source-version r2)))

  (fold (lambda (release result)
          (match result
            ((head . tail)
             (if (same-version? release head)
                 (cons (upstream-source
                        (inherit release)
                        (urls (append (upstream-source-urls release)
                                      (upstream-source-urls head)))
                        (signature-urls
                         (let ((one (upstream-source-signature-urls release))
                               (two (upstream-source-signature-urls head)))
                           (and one two (append one two)))))
                       tail)
                 (cons release result)))
            (()
             (list release))))
        '()
        (sort sources release>?)))

\f
;;;
;;; Auto-update.
;;;

(define-record-type* <upstream-updater>
  upstream-updater make-upstream-updater
  upstream-updater?
  (name        upstream-updater-name)
  (description upstream-updater-description)
  (pred        upstream-updater-predicate)
  (import      upstream-updater-import))

(define (importer-modules)
  "Return the list of importer modules."
  (cons (resolve-interface '(guix gnu-maintenance))
        (all-modules (map (lambda (entry)
                            `(,entry . "guix/import"))
                          %load-path)
                     #:warn warn-about-load-error)))

(define %updaters
  ;; The list of publically-known updaters, alphabetically sorted.
  (delay
    (let* ((updaters
            (sort (fold-module-public-variables
                   (lambda (obj result)
                     (if (upstream-updater? obj)
                         (cons obj result)
                         result))
                   '()
                   (importer-modules))
                  (lambda (updater1 updater2)
                    (string<?
                     (symbol->string (upstream-updater-name updater1))
                     (symbol->string (upstream-updater-name updater2))))))
           (generic-updaters rest (partition
                                   (compose (cut string-prefix? "generic" <>)
                                            symbol->string
                                            upstream-updater-name)
                                   updaters)))
      ;; Ensure the generic updaters are tried last, as otherwise they could
      ;; return less accurate results.
      (append rest generic-updaters))))

;; Tests need to mock this variable so mark it as "non-declarative".
(set! %updaters %updaters)

(define* (lookup-updater package
                         #:optional (updaters (force %updaters)))
  "Return an updater among UPDATERS that matches PACKAGE, or #f if none of
them matches."
  (find (match-lambda
          (($ <upstream-updater> name description pred import)
           (pred package)))
        updaters))

(define* (package-latest-release package
                                 #:optional
                                 (updaters (force %updaters))
                                 #:key (version #f))
  "Return an upstream source to update PACKAGE, a <package> object, or #f if
none of UPDATERS matches PACKAGE.  When several updaters match PACKAGE, try
them until one of them returns an upstream source.  It is the caller's
responsibility to ensure that the returned source is newer than the current
one."
  (any (match-lambda
         (($ <upstream-updater> name description pred import)
          (and (pred package)
               (import package #:version version))))
       updaters))

(define* (package-latest-release* package
                                  #:optional
                                  (updaters (force %updaters)))
  "Like 'package-latest-release', but ensure that the return source is newer
than that of PACKAGE."
  (match (package-latest-release package updaters)
    ((and source ($ <upstream-source> name version))
     (and (version>? version (package-version package))
          source))
    (_
     #f)))

(define (uncompressed-tarball name tarball)
  "Return a derivation that decompresses TARBALL."
  (define (ref package)
    (module-ref (resolve-interface '(gnu packages compression))
                package))

  (define compressor
    (cond ((or (string-suffix? ".gz" tarball)
               (string-suffix? ".tgz" tarball))
           (file-append (ref 'gzip) "/bin/gzip"))
          ((string-suffix? ".bz2" tarball)
           (file-append (ref 'bzip2) "/bin/bzip2"))
          ((string-suffix? ".xz" tarball)
           (file-append (ref 'xz) "/bin/xz"))
          ((string-suffix? ".lz" tarball)
           (file-append (ref 'lzip) "/bin/lzip"))
          (else
           (error "unknown archive type" tarball))))

  (gexp->derivation (file-sans-extension name)
                    #~(begin
                        (copy-file #+tarball #+name)
                        (and (zero? (system* #+compressor "-d" #+name))
                             (copy-file #+(file-sans-extension name)
                                        #$output)))))

(define* (download-tarball store url signature-url
                           #:key (key-download 'interactive) key-server)
  "Download the tarball at URL to the store; check its OpenPGP signature at
SIGNATURE-URL, unless SIGNATURE-URL is false.  On success, return the tarball
file name; return #f on failure (network failure or authentication failure).

KEY-DOWNLOAD specifies a download policy for missing OpenPGP keys; allowed
values: 'interactive' (default), 'always', and 'never'; KEY-SERVER specifies
the OpenPGP key server where the key should be looked up."
  (let ((tarball (download-to-store store url)))
    (if (not signature-url)
        tarball
        (let* ((sig  (download-to-store store signature-url))

               ;; Sometimes we get a signature over the uncompressed tarball.
               ;; In that case, decompress the tarball in the store so that we
               ;; can check the signature.
               (data (if (string-prefix? (basename url)
                                         (basename signature-url))
                         tarball
                         (run-with-store store
                           (mlet %store-monad ((drv (uncompressed-tarball
                                                     (basename url) tarball)))
                             (mbegin %store-monad
                               (built-derivations (list drv))
                               (return (derivation->output-path drv))))))))
          (let ((status data (if sig
                                 (gnupg-verify* sig data
                                                #:server key-server
                                                #:key-download key-download)
                                 (values 'missing-signature data))))
            (match status
              ('valid-signature
               tarball)
              ('missing-signature
               (warning (G_ "failed to download detached signature from ~a~%")
                        signature-url)
               #f)
              ('invalid-signature
               (warning (G_ "signature verification failed for '~a' (key: ~a)~%")
                        url data)
               #f)
              ('missing-key
               (warning (G_ "missing public key ~a for '~a'~%")
                        data url)
               #f)))))))

(define (upstream-source-compiler/url-fetch source system)
  "Lower SOURCE, an <upstream-source> pointing to a tarball, as a
fixed-output derivation that would fetch it, and verify its authenticity."
  (mlet* %store-monad ((url -> (first (upstream-source-urls source)))
                       (signature
                        -> (and=> (upstream-source-signature-urls source)
                                  first))
                       (tarball ((store-lift download-tarball) url signature)))
    (unless tarball
      (raise (formatted-message (G_ "failed to fetch source from '~a'")
                                url)))

    ;; Instead of returning TARBALL, return a fixed-output derivation that
    ;; would be able to re-download it.  In practice, since TARBALL is already
    ;; in the store, no extra download will happen, but having the derivation
    ;; in store improves provenance tracking.
    (let ((hash (call-with-input-file tarball port-sha256)))
      (url-fetch url 'sha256 hash (store-path-package-name tarball)
                 #:system system))))

(define (upstream-source-compiler/git-fetch source system)
  "Lower SOURCE, an <upstream-source> using git, as a fixed-output
derivation that would fetch it."
  (mlet* %store-monad ((reference -> (upstream-source-urls source))
                       (checkout
                        (lower-object
                         (git-reference->git-checkout reference)
                         system)))
    ;; Like in 'upstream-source-compiler/url-fetch', return a fixed-output
    ;; derivation instead of CHECKOUT.
    (git-fetch reference 'sha256
               (file-hash* checkout #:recursive? #true #:select? (const #true))
               (git-file-name (upstream-source-package source)
                              (upstream-source-version source))
               #:system system)))

(define-gexp-compiler (upstream-source-compiler (source <upstream-source>)
                                                system target)
  "Download SOURCE, lower it as a fixed-output derivation that would fetch it,
and verify its authenticity if possible."
  (if (git-reference? (upstream-source-urls source))
      (upstream-source-compiler/git-fetch source system)
      (upstream-source-compiler/url-fetch source system)))

(define (find2 pred lst1 lst2)
  "Like 'find', but operate on items from both LST1 and LST2.  Return two
values: the item from LST1 and the item from LST2 that match PRED."
  (let loop ((lst1 lst1) (lst2 lst2))
    (match lst1
      ((head1 . tail1)
       (match lst2
         ((head2 . tail2)
          (if (pred head1 head2)
              (values head1 head2)
              (loop tail1 tail2)))))
      (()
       (values #f #f)))))

(define (package-archive-type package)
  "If PACKAGE's source is a tarball or zip archive, return its archive type--a
string such as \"xz\".  Otherwise return #f."
  (match (and=> (package-source package) origin-actual-file-name)
    (#f #f)
    (file
     (let ((extension (file-extension file)))
       ;; FILE might be "example-1.2-checkout", in which case we want to
       ;; ignore the extension.
       (and (or (string-contains extension "z")
                (string-contains extension "tar"))
            extension)))))

(define (preferred-upstream-source-url source package)
  "Return two values: a source URL that matches the archive type of
PACKAGE (gz, xz, bz2, etc.) and the corresponding signature URL or #f if there
is no signature.  Return #f and #f when this is not applicable."
  (let ((archive-type (package-archive-type package)))
    (find2 (lambda (url sig-url)
             ;; Some URIs lack a file extension, like
             ;; 'https://crates.io/???/0.1/download'.  In that case, pick the
             ;; first URL.
             (or (not archive-type)
                 (string-suffix? archive-type url)))
           (upstream-source-urls source)
           (or (upstream-source-signature-urls source)
               (circular-list #f)))))

(define* (package-update/url-fetch store package source
                                   #:key key-download key-server)
  "Return the version, tarball, and SOURCE, to update PACKAGE to
SOURCE, an <upstream-source>."
  (match source
    (($ <upstream-source> _ version urls signature-urls)
     (let ((url signature-url
                (preferred-upstream-source-url source package)))
       ;; If none of URLS matches ARCHIVE-TYPE, then URL is #f; in that case,
       ;; pick up the first element of URLS.
       (let ((tarball (download-tarball store
                                        (or url (first urls))
                                        (and (pair? signature-urls)
                                             (or signature-url
                                                 (first signature-urls)))
                                        #:key-server key-server
                                        #:key-download key-download)))
         (values version tarball source))))))


(define* (package-update/git-fetch store package source
                                   #:key key-download key-server)
  "Return the version, checkout, and SOURCE, to update PACKAGE to
SOURCE, an <upstream-source>."
  ;; TODO: it would be nice to authenticate commits, e.g. with
  ;; "guix git authenticate" or a list of permitted signing keys.
  (define ref (upstream-source-urls source)) ; a <git-reference>
  (values (upstream-source-version source)
          (latest-repository-commit
           store
           (git-reference-url ref)
           #:ref `(tag-or-commit . ,(git-reference-commit ref))
           #:recursive? (git-reference-recursive? ref))
          source))

(define* (package-update/svn-multi-fetch store package source
                                         #:key key-download key-server)
  "Return the version, checkout, and SOURCE, to update PACKAGE to
SOURCE, an <upstream-source>."
  (values (upstream-source-version source)
          (download-multi-svn-to-store store (upstream-source-urls source))
          source))

(define %method-updates
  ;; Mapping of origin methods to source update procedures.
  `((,url-fetch . ,package-update/url-fetch)
    (,git-fetch . ,package-update/git-fetch)
    (,svn-multi-fetch . ,package-update/svn-multi-fetch)))

(define* (package-update store package
                         #:optional (updaters (force %updaters))
                         #:key (version #f)
                         (key-download 'interactive) key-server)
  "Return the new version, the file name of the new version tarball, and input
changes for PACKAGE; return #f (three values) when PACKAGE is up-to-date;
raise an error when the updater could not determine available releases.
KEY-DOWNLOAD specifies a download policy for missing OpenPGP keys; allowed
values: 'always', 'never', and 'interactive' (default).

When VERSION is specified, update PACKAGE to that version, even if that is a
downgrade."
  (match (package-latest-release package updaters #:version version)
    ((? upstream-source? source)
     (if (or (version>? (upstream-source-version source)
                        (package-version package))
             (and version
                  (begin
                    (warning (package-location package)
                             (G_ "downgrading '~a' from ~a to ~a~%")
                             (package-name package)
                             (package-version package)
                             (upstream-source-version source))
                    #t)))
         (let ((method (match (package-source package)
                         ((? origin? origin)
                          (origin-method origin))
                         (_
                          #f))))
           (match (assq method %method-updates)
             (#f
              (raise (make-compound-condition
                      (formatted-message (G_ "cannot download for \
this method: ~s")
                                         method)
                      (condition
                       (&error-location
                        (location (package-location package)))))))
             ((_ . update)
              (update store package source
                      #:key-server key-server
                      #:key-download key-download))))
         (values #f #f #f)))
    (#f
     ;; Warn rather than abort so that other updates can still take place.
     (if version
         (warning (G_ "updater failed to find release ~a@~a~%")
                  (package-name package) version)
         (warning (G_ "updater failed to determine available releases for ~a~%")
                  (package-name package)))
     (values #f #f #f))))

(define (update-package-inputs package source)
  "Update the input fields of the definition of PACKAGE according to those
specified in SOURCE, an <upstream-source>."
  (define (update-field field source-inputs package-inputs)
    (define loc
      (package-field-location package field))

    (define new
      (map (compose string->symbol upstream-input-downstream-name)
           (source-inputs source)))

    (define old
      (match (package-inputs package)
        (((labels (? package? packages)) ...)
         labels
         (map string->symbol labels))
        (_
         '())))

    (define unchanged?
      (equal? new old))

    (if (and loc (not unchanged?))
        (edit-expression (location->source-properties
                          (absolute-location loc))
                         (lambda (str)
                           (object->string* `(list ,@new)
                                            (location-column loc))))
        (unless unchanged?
          ;; XXX: Bail out when FIELD isn't already present in the source.
          ;; TODO: Add the field if it's missing.
          (warning (package-location package)
                   (G_ "~a: '~a' field not found; leaving it unchanged~%")
                   (package-name package) field)
          (warning (package-location package)
                   (G_ "~a: expected '~a' value: ~s~%")
                   (package-name package) field new))))

  (define (filtered-inputs source-inputs extra-property ignore-property)
    ;; Return a procedure that behaves like SOURCE-INPUTS but additionally
    ;; honors EXTRA-PROPERTY and IGNORE-PROPERTY from PACKAGE.
    (lambda (source)
      (let* ((inputs (source-inputs source))
             (properties (package-properties package))
             (ignore (or (assoc-ref properties ignore-property) '()))
             (extra (or (assoc-ref properties extra-property) '())))
        (sort
         (append (if (null? ignore)
                     inputs
                     (remove (lambda (input)
                               (member (upstream-input-downstream-name input)
                                       ignore))
                             inputs))
                 (map (lambda (name)
                        (upstream-input
                         (name name)
                         (downstream-name name)))
                      extra))
         (lambda (a b)
           (string-ci<? (upstream-input-downstream-name a)
                        (upstream-input-downstream-name b)))))))

  (define regular-inputs
    (filtered-inputs upstream-source-regular-inputs
                     'updater-extra-inputs
                     'updater-ignored-inputs))
  (define native-inputs
    (filtered-inputs upstream-source-native-inputs
                     'updater-extra-native-inputs
                     'updater-ignored-native-inputs))
  (define propagated-inputs
    (filtered-inputs upstream-source-propagated-inputs
                     'updater-extra-propagated-inputs
                     'updater-ignored-propagated-inputs))

  (for-each update-field
            '(inputs native-inputs propagated-inputs)
            (list regular-inputs
                  native-inputs
                  propagated-inputs)
            (list package-inputs
                  package-native-inputs
                  package-propagated-inputs)))

(define* (update-package-source package source hash)
  "Modify the source file that defines PACKAGE to refer to SOURCE, an
<upstream-source> whose tarball has SHA256 HASH (a bytevector).  Return the
new version string if an update was made, and #f otherwise."
  (define (replace-atom expr replacements)
    ;; Apply REPLACEMENTS to package expression EXPR, a string.  REPLACEMENTS
    ;; must be a list of replacement pairs, either of byte-vectors or strings.
    (fold (lambda (replacement str)
            (match replacement
              (((? bytevector? old-bv) . (? bytevector? new-bv))
               (string-replace-substring
                str
                (bytevector->nix-base32-string old-bv)
                (bytevector->nix-base32-string new-bv)))
              ((old . new)
               (string-replace-substring str old new))))
          expr
          replacements))

  (define (replace-commit old new expr)
    ;; Replace OLD commit or revision with NEW commit or revision in package
    ;; expression EXPR.  Special care is given to ensure the commit or
    ;; revision does not inadvertently match a part of a bigger item.
    (let ((regexp (make-regexp (format #f " ~s($|[ )])" old)
                               regexp/newline)))
      (regexp-substitute/global
       #f regexp expr 'pre (lambda (m) (format #f " ~s" new)) 1 'post)))

  (define (replace-list old new expr)
    ;; Replace list OLD with list NEW in package expression EXPR.  Elements in
    ;; NEW are aligned vertically, at the same column as the first element in
    ;; OLD.
    (if (equal? old new)
        expr
        (let ((regexp
               (make-regexp
                (string-append
                 "(^[^\"]*)"            ;initial indentation in group 1
                 (string-join (map (compose regexp-quote object->string) old)
                              "[ \t\n]*"))
                regexp/newline))
              (f
               (lambda (m)
                 (let* ((lead (match:substring m 1))
                        (indent (make-string (string-length lead) #\space)))
                   (string-append
                    lead
                    (string-join (map object->string new)
                                 (string-append "\n" indent)))))))
          (regexp-substitute/global #f regexp expr 'pre f 'post))))

  (let* ((name        (package-name package))
         (loc         (package-location package))
         (version     (upstream-source-version source))
         (old-version (package-version package))
         (old-hash    (content-hash-value
                       (origin-hash (package-source package))))
         (old-url     (match (origin-uri (package-source package))
                        ((? string? url) url)
                        ((? git-reference? ref)
                         (git-reference-url ref))
                        ((? svn-multi-reference? ref)
                         (svn-multi-reference-url ref))
                        (_ #f)))
         (old-commit  (match (origin-uri (package-source package))
                        ((? git-reference? ref)
                         (git-reference-commit ref))
                        ((? svn-multi-reference? ref)
                         (svn-multi-reference-revision ref))
                        (_ #f)))
         (old-locations (match (origin-uri (package-source package))
                          ((? svn-multi-reference? ref)
                           (svn-multi-reference-locations ref))
                          (_ #f)))
         (new-url     (match (upstream-source-urls source)
                        ((first _ ...) first)
                        ((? git-reference? ref)
                         (git-reference-url ref))
                        ((? svn-multi-reference? ref)
                         (svn-multi-reference-url ref))
                        (_ #f)))
         (new-commit  (match (upstream-source-urls source)
                        ((? git-reference? ref)
                         (git-reference-commit ref))
                        ((? svn-multi-reference? ref)
                         (svn-multi-reference-revision ref))
                        (_ #f)))
         (new-locations (match (upstream-source-urls source)
                          ((? svn-multi-reference? ref)
                           (svn-multi-reference-locations ref))
                          (_ #f))))
    (cond
     ;; Ensure package exists, has a version field, and is stored in a file
     ;; with an absolute file name.
     ((not (package-field-location package 'version))
      (warning (package-location package)
               (G_ "~a: no `version' field in source; skipping~%")
               name))
     ((not (and=> (location-file loc)
                  (cut search-path %load-path <>)))
      (warning (G_ "~a: could not locate source file")
               (location-file loc))
      #f)
     ;; Proceed with replacements.
     (else
      (let ((replacement-pairs
             `((,old-version . ,version)
               (,old-hash . ,hash)
               ;; Replace the URL directory when OLD-URL is available; this is
               ;; useful notably for mirror://cpan/ URLs where the directory
               ;; may change as a function of the person who uploads the
               ;; package.  Note that package definitions usually concatenate
               ;; fragments of the URL, which is why we only attempt to
               ;; replace a subset of the URL.
               ,@(if (and old-url new-url)
                     `((,(dirname old-url) . ,(dirname new-url)))
                     '()))))
        (and (edit-expression
              (location->source-properties (absolute-location loc))
              (compose (cut replace-atom <> replacement-pairs)
                       (cut replace-commit old-commit new-commit <>)
                       (cut replace-list old-locations new-locations <>)))
             (or (not (upstream-source-inputs source))
                 (update-package-inputs package source))
             version))))))

;;; upstream.scm ends here