[bug#44178] [PATCHv3] Create importer for Go modules

["JOULAUD François via Guix-patches via" <guix-patches@gnu.org>]

This patch add a `guix import go` command.

It was tested with several big repositories and mostly works. Several
features are lacking (see TODO in source code) but we will do the
improvments step-by-step in future patches.

* doc/guix.texi: doc about go importer and guile-lib dependency
* gnu/packages/package-management.scm: added guile-lib dependency
* guix/self.scm: add guile-lib dependency
* guix/build-system/go.scm: go-version->git-ref function
* guix/import/go.scm: Created Go importer
* guix/scripts/import/go.scm: Subcommand for Go importer
* guix/scripts/import.scm: Declare subcommand guix import go
* tests/import-go.scm: Tests for parse-go.mod procedure

Signed-off-by: Francois Joulaud <francois.joulaud@radiofrance.com>
---
 doc/guix.texi                       |  26 ++
 gnu/packages/package-management.scm |   2 +
 guix/build-system/go.scm            |  35 ++-
 guix/import/go.scm                  | 416 ++++++++++++++++++++++++++++
 guix/scripts/import.scm             |   2 +-
 guix/scripts/import/go.scm          | 118 ++++++++
 guix/self.scm                       |   5 +-
 tests/import-go.scm                 | 144 ++++++++++
 8 files changed, 745 insertions(+), 3 deletions(-)
 create mode 100644 guix/import/go.scm
 create mode 100644 guix/scripts/import/go.scm
 create mode 100644 tests/import-go.scm

diff --git a/doc/guix.texi b/doc/guix.texi
index 5d28fca837..89c8abd261 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -861,6 +861,10 @@ substitutes (@pxref{Invoking guix publish}).
 @uref{https://ngyro.com/software/guile-semver.html, Guile-Semver} for
 the @code{crate} importer (@pxref{Invoking guix import}).
 
+@item
+@uref{https://www.nongnu.org/guile-lib/doc/ref/htmlprag/, guile-lib} for
+the @code{crate} importer (@pxref{Invoking guix import}).
+
 @item
 When @url{http://www.bzip.org, libbz2} is available,
 @command{guix-daemon} can use it to compress build logs.
@@ -11493,6 +11497,28 @@ Select the given repository (a repository name).  Possible values include:
       of coq packages.
 @end itemize
 @end table
+
+@item go
+@cindex go
+Import metadata for a Go module using
+@uref{https://proxy.golang.org, proxy.golang.org}.
+
+This importer is highly experimental. See the source code for more info
+about the current state.
+
+@example
+guix import go gopkg.in/yaml.v2
+@end example
+
+Additional options include:
+
+@table @code
+@item --recursive
+@itemx -r
+Traverse the dependency graph of the given upstream package recursively
+and generate package expressions for all those packages that are not yet
+in Guix.
+@end table
 @end table
 
 The structure of the @command{guix import} code is modular.  It would be
diff --git a/gnu/packages/package-management.scm b/gnu/packages/package-management.scm
index 9fb8c40a31..06bb5bd2df 100644
--- a/gnu/packages/package-management.scm
+++ b/gnu/packages/package-management.scm
@@ -304,6 +304,7 @@ $(prefix)/etc/init.d\n")))
                                              '((assoc-ref inputs "guile"))))
                                (avahi  (assoc-ref inputs "guile-avahi"))
                                (gcrypt (assoc-ref inputs "guile-gcrypt"))
+                               (guile-lib   (assoc-ref inputs "guile-lib"))
                                (json   (assoc-ref inputs "guile-json"))
                                (sqlite (assoc-ref inputs "guile-sqlite3"))
                                (zlib   (assoc-ref inputs "guile-zlib"))
@@ -367,6 +368,7 @@ $(prefix)/etc/init.d\n")))
                              `(("guile-avahi" ,guile-avahi)))
                        ("guile-gcrypt" ,guile-gcrypt)
                        ("guile-json" ,guile-json-4)
+                       ("guile-lib" ,guile-lib)
                        ("guile-sqlite3" ,guile-sqlite3)
                        ("guile-zlib" ,guile-zlib)
                        ("guile-lzlib" ,guile-lzlib)
diff --git a/guix/build-system/go.scm b/guix/build-system/go.scm
index f8ebaefb27..594e0cb4f3 100644
--- a/guix/build-system/go.scm
+++ b/guix/build-system/go.scm
@@ -26,9 +26,42 @@
   #:use-module (guix build-system gnu)
   #:use-module (guix packages)
   #:use-module (ice-9 match)
+  #:use-module (ice-9 regex)
   #:export (%go-build-system-modules
             go-build
-            go-build-system))
+            go-build-system
+
+            go-version->git-ref))
+
+(define (go-version->git-ref version)
+  "GO-VERSION->GIT-REF parse pseudo-versions and extract the commit
+   hash from it, defaulting to full VERSION if we don't recognise a
+   pseudo-version pattern."
+  ;; A module version like v1.2.3 is introduced by tagging a revision in
+  ;; the underlying source repository. Untagged revisions can be referred
+  ;; to using a "pseudo-version" like v0.0.0-yyyymmddhhmmss-abcdefabcdef,
+  ;; where the time is the commit time in UTC and the final suffix is the
+  ;; prefix of the commit hash.
+  ;; cf. https://golang.org/cmd/go/#hdr-Pseudo_versions
+  (let* ((version
+          ;; if a source code repository has a v2.0.0 or later tag for
+          ;; a file tree with no go.mod, the version is considered to be
+          ;; part of the v1 module's available versions and is given an
+          ;; +incompatible suffix
+          ;; https://golang.org/cmd/go/#hdr-Module_compatibility_and_semantic_versioning
+          (if (string-suffix? "+incompatible" version)
+              (string-drop-right version 13)
+              version))
+         (re (string-concatenate
+              (list
+               "(v?[0-9]\\.[0-9]\\.[0-9])" ; "v" prefix can be omitted in version prefix
+               "(-|-pre\\.0\\.|-0\\.)"     ; separator
+               "([0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9])-" ; timestamp
+               "([0-9A-Fa-f][0-9A-Fa-f][0-9A-Fa-f][0-9A-Fa-f][0-9A-Fa-f][0-9A-Fa-f][0-9A-Fa-f][0-9A-Fa-f][0-9A-Fa-f][0-9A-Fa-f][0-9A-Fa-f][0-9A-Fa-f])"))) ; commit hash
+         (match (string-match re version)))
+    (if match
+        (match:substring match 4)
+        version)))
 
 ;; Commentary:
 ;;
diff --git a/guix/import/go.scm b/guix/import/go.scm
new file mode 100644
index 0000000000..fead355bd2
--- /dev/null
+++ b/guix/import/go.scm
@@ -0,0 +1,416 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2020 Katherine Cox-Buday <cox.katherine.e@gmail.com>
+;;; Copyright © 2020 Helio Machado <0x2b3bfa0+guix@googlemail.com>
+;;; Copyright © 2021 François Joulaud <francois.joulaud@radiofrance.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/>.
+
+;;; (guix import golang) wants to make easier to create Guix package
+;;; declaration for Go modules.
+;;;
+;;; Modules in Go are "collection of related Go packages" which are
+;;; "the unit of source code interchange and versioning".
+;;; Modules are generally hosted in a repository.
+;;;
+;;; At this point it should handle correctly modules which
+;;; have only Go dependencies and are accessible from proxy.golang.org
+;;; (or configured GOPROXY).
+;;;
+;;; We want it to work more or less this way:
+;;; - get latest version for the module from GOPROXY
+;;; - infer VCS root repo from which we will check-out source by
+;;;   + recognising known patterns (like github.com)
+;;;   + or (TODO) recognising .vcs suffix
+;;;   + or parsing meta tag in html served at the URL
+;;;   + or (TODO) if nothing else works by using zip file served by GOPROXY
+;;; - get go.mod from GOPROXY (which is able to synthetize one if needed)
+;;; - extract list of dependencies from this go.mod
+;;;
+;;; We translate Go module paths to a Guix package name under the
+;;; assumption that there will be no collision.
+
+;;; TODO list
+;;; - get correct hash in vcs->origin
+;;; - print partial result during recursive imports (need to catch
+;;;   exceptions)
+;;; - infer repo from module path with VCS qualifier
+;;;   (e.g. site.example/my/path/to/repo.git/and/subdir/module)
+;;; - don't print fetch messages to stdout
+;;; - pre-fill synopsis, description and license
+
+(define-module (guix import go)
+  #:use-module (ice-9 match)
+  #:use-module (ice-9 rdelim)
+  #:use-module (ice-9 receive)
+  #:use-module (ice-9 regex)
+  #:use-module (guix build-system go)
+  #:use-module (htmlprag)
+  #:use-module (sxml xpath)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-9)
+  #:use-module (srfi srfi-11)
+  #:use-module (json)
+  #:use-module ((guix download) #:prefix download:)
+  #:use-module (guix git)
+  #:use-module (guix import utils)
+  #:use-module (guix import json)
+  #:use-module (guix packages)
+  #:use-module (guix upstream)
+  #:use-module (guix utils)
+  #:use-module ((guix licenses) #:prefix license:)
+  #:use-module (guix base16)
+  #:use-module (guix base32)
+  #:use-module (guix memoization)
+  #:use-module ((guix build download) #:prefix build-download:)
+  #:use-module (web uri)
+
+  #:export (go-module->guix-package
+            go-module-recursive-import
+            infer-module-root-repo))
+
+
+(define (go-path-escape path)
+  "Escape a module path by replacing every uppercase letter with an exclamation
+mark followed with its lowercase equivalent, as per the module Escaped Paths
+specification. https://godoc.org/golang.org/x/mod/module#hdr-Escaped_Paths"
+  (define (escape occurrence)
+    (string-append "!" (string-downcase (match:substring occurrence))))
+  (regexp-substitute/global #f "[A-Z]" path 'pre escape 'post))
+
+
+(define (go-module-latest-version goproxy-url module-path)
+  "Fetches the version number of the latest version for MODULE-PATH from the
+given GOPROXY-URL server."
+  (assoc-ref
+   (json-fetch (format #f "~a/~a/@latest" goproxy-url
+                       (go-path-escape module-path)))
+   "Version"))
+
+(define go-module-latest-version* (memoize go-module-latest-version))
+
+(define (fetch-go.mod goproxy-url module-path version file)
+  "Fetches go.mod from the given GOPROXY-URL server for the given MODULE-PATH
+and VERSION."
+  (let ((url (format #f "~a/~a/@v/~a.mod" goproxy-url
+                     (go-path-escape module-path)
+                     (go-path-escape version))))
+    (parameterize ((current-output-port (current-error-port)))
+      (build-download:url-fetch url
+                                file
+                                #:print-build-trace? #f))))
+
+(define (parse-go.mod go.mod-path)
+  (parse-go.mod-port (open-input-file go.mod-path)))
+
+(define (parse-go.mod-port go.mod-port)
+  "PARSE-GO.MOD takes a filename in GO.MOD-PATH and extract a list of
+requirements from it."
+  ;; We parse only a subset of https://golang.org/ref/mod#go-mod-file-grammar
+  ;; which we think necessary for our use case.
+  (define (toplevel results)
+    "Main parser, RESULTS is a pair of alist serving as accumulator for
+     all encountered requirements and replacements."
+    (let ((line (read-line)))
+      (cond
+       ((eof-object? line)
+        ;; parsing ended, give back the result
+        results)
+       ((string=? line "require (")
+        ;; a require block begins, delegate parsing to IN-REQUIRE
+        (in-require results))
+       ((string=? line "replace (")
+        ;; a replace block begins, delegate parsing to IN-REPLACE
+        (in-replace results))
+       ((string-prefix? "require " line)
+        ;; a require directive by itself
+        (let* ((stripped-line (string-drop line 8))
+               (new-results (require-directive results stripped-line)))
+          (toplevel new-results)))
+       ((string-prefix? "replace " line)
+        ;; a replace directive by itself
+        (let* ((stripped-line (string-drop line 8))
+               (new-results (replace-directive results stripped-line)))
+          (toplevel new-results)))
+       (#t
+        ;; unrecognised line, ignore silently
+        (toplevel results)))))
+  (define (in-require results)
+    (let ((line (read-line)))
+      (cond
+       ((eof-object? line)
+        ;; this should never happen here but we ignore silently
+        results)
+       ((string=? line ")")
+        ;; end of block, coming back to toplevel
+        (toplevel results))
+       (#t
+        (in-require (require-directive results line))))))
+  (define (in-replace results)
+    (let ((line (read-line)))
+      (cond
+       ((eof-object? line)
+        ;; this should never happen here but we ignore silently
+        results)
+       ((string=? line ")")
+        ;; end of block, coming back to toplevel
+        (toplevel results))
+       (#t
+        (in-replace (replace-directive results line))))))
+  (define (replace-directive results line)
+    "Extract replaced modules and new requirements from replace directive
+    in LINE and add to RESULTS."
+    ;; ReplaceSpec = ModulePath [ Version ] "=>" FilePath newline
+    ;;             | ModulePath [ Version ] "=>" ModulePath Version newline .
+    (let* ((requirements (car results))
+           (replaced (cdr results))
+           (re (string-concatenate
+                '("([^[:blank:]]+)([[:blank:]]+([^[:blank:]]+))?"
+                  "[[:blank:]]+" "=>" "[[:blank:]]+"
+                  "([^[:blank:]]+)([[:blank:]]+([^[:blank:]]+))?")))
+           (match (string-match re line))
+           (module-path (match:substring match 1))
+           (version (match:substring match 3))
+           (new-module-path (match:substring match 4))
+           (new-version (match:substring match 6))
+           (new-replaced (acons module-path version replaced))
+           (new-requirements
+            (if (string-match "^\\.?\\./" new-module-path)
+                requirements
+                (acons new-module-path new-version requirements))))
+      (cons new-requirements new-replaced)))
+  (define (require-directive results line)
+    "Extract requirement from LINE and add it to RESULTS."
+    (let* ((requirements (car results))
+           (replaced (cdr results))
+           ;; A line in a require directive is composed of a module path and
+           ;; a version separated by whitespace and an optionnal '//' comment at
+           ;; the end.
+           (re (string-concatenate
+                '("^[[:blank:]]*"
+                  "([^[:blank:]]+)[[:blank:]]+([^[:blank:]]+)"
+                  "([[:blank:]]+//.*)?")))
+           (match (string-match re line))
+           (module-path (match:substring match 1))
+           ;; we saw double-quoted string in the wild without escape
+           ;; sequences so we just trim the quotes
+           (module-path (string-trim-both module-path #\"))
+           (version (match:substring match 2)))
+      (cons (acons module-path version requirements) replaced)))
+  (with-input-from-port go.mod-port
+    (lambda ()
+      (let* ((results (toplevel '(() . ())))
+             (requirements (car results))
+             (replaced (cdr results)))
+        ;; At last we remove replaced modules from the requirements list
+        (fold
+         (lambda (replacedelem requirements)
+           (alist-delete! (car replacedelem) requirements))
+         requirements
+         replaced)))))
+
+(define (infer-module-root-repo module-path)
+  "Go modules can be defined at any level of a repository's tree, but querying
+for the meta tag usually can only be done at the webpage at the root of the
+repository. Therefore, it is sometimes necessary to try and derive a module's
+root path from its path. For a set of well-known forges, the pattern of what
+consists of a module's root page is known before hand."
+  ;; See the following URL for the official Go equivalent:
+  ;; https://github.com/golang/go/blob/846dce9d05f19a1f53465e62a304dea21b99f910/src/cmd/go/internal/vcs/vcs.go#L1026-L1087
+  ;;
+  ;; TODO: handle module path with VCS qualifier as described in
+  ;; https://golang.org/ref/mod#vcs-find and
+  ;; https://golang.org/cmd/go/#hdr-Remote_import_paths
+  (define-record-type <vcs>
+    (make-vcs url-prefix root-regex type)
+    vcs?
+    (url-prefix vcs-url-prefix)
+    (root-regex vcs-root-regex)
+    (type vcs-type))
+  (let* ((known-vcs
+          (list
+           (make-vcs
+            "github.com"
+            "^(github\\.com/[A-Za-z0-9_.\\-]+/[A-Za-z0-9_.\\-]+)(/[A-Za-z0-9_.\\-]+)*$"
+            'git)
+           (make-vcs
+            "bitbucket.org"
+            "^(bitbucket\\.org/([A-Za-z0-9_.\\-]+/[A-Za-z0-9_.\\-]+))(/[A-Za-z0-9_.\\-]+)*$"
+            'unknown)
+           (make-vcs
+            "hub.jazz.net/git/"
+            "^(hub\\.jazz\\.net/git/[a-z0-9]+/[A-Za-z0-9_.\\-]+)(/[A-Za-z0-9_.\\-]+)*$"
+            'git)
+           (make-vcs
+            "git.apache.org"
+            "^(git\\.apache\\.org/[a-z0-9_.\\-]+\\.git)(/[A-Za-z0-9_.\\-]+)*$"
+            'git)
+           (make-vcs
+            "git.openstack.org"
+            "^(git\\.openstack\\.org/[A-Za-z0-9_.\\-]+/[A-Za-z0-9_.\\-]+)(\\.git)?(/[A-Za-z0-9_.\\-]+)*$"
+            'git)))
+         (vcs (find (lambda (vcs) (string-prefix? (vcs-url-prefix vcs) module-path))
+                    known-vcs)))
+    (if vcs
+        (match:substring (string-match (vcs-root-regex vcs) module-path) 1)
+        module-path)))
+
+(define (go-module->guix-package-name module-path)
+  "Converts a module's path to the canonical Guix format for Go packages."
+  (string-downcase
+   (string-append "go-"
+                  (string-replace-substring
+                   (string-replace-substring
+                    module-path
+                    "." "-")
+                   "/" "-"))))
+
+(define-record-type <module-meta>
+  (make-module-meta import-prefix vcs repo-root)
+  module-meta?
+  (import-prefix module-meta-import-prefix)
+  ;; VCS field is a symbol
+  (vcs module-meta-vcs)
+  (repo-root module-meta-repo-root))
+
+(define (fetch-module-meta-data module-path)
+  "Fetches module meta-data from a module's landing page. This is
+  necessary because goproxy servers don't currently provide all the
+  information needed to build a package."
+  ;; <meta name="go-import" content="import-prefix vcs repo-root">
+  (define (meta-go-import->module-meta text)
+    "Takes the content of the go-import meta tag as TEXT and gives back
+     a MODULE-META record"
+    (define (get-component s start)
+      (let*
+          ((start (string-skip s char-set:whitespace start))
+           (end (string-index s char-set:whitespace start))
+           (end (if end end (string-length s)))
+           (result (substring s start end)))
+        (values result end)))
+    (let*-values (((import-prefix end) (get-component text 0))
+                  ((vcs end) (get-component text end))
+                  ((repo-root end) (get-component text end)))
+      (make-module-meta import-prefix (string->symbol vcs) repo-root)))
+  (define (html->meta-go-import port)
+    "Read PORT with HTML content. Find the go-import meta tag and gives
+    back its content as a string."
+    (let* ((parsedhtml (html->sxml port))
+           (extract-content (node-join
+                             (select-kids (node-typeof? 'html))
+                             (select-kids (node-typeof? 'head))
+                             (select-kids (node-typeof? 'meta))
+                             (select-kids (node-typeof? '@))
+                             (node-self
+                              (node-join
+                               (select-kids (node-typeof? 'name))
+                               (select-kids (node-equal? "go-import"))))
+                             (select-kids (node-typeof? 'content))
+                             (select-kids (lambda (_) #t))))
+           (content (car (extract-content parsedhtml))))
+      content))
+  (let* ((port (build-download:http-fetch (string->uri (format #f "https://~a?go-get=1" module-path))))
+         (meta-go-import (html->meta-go-import port))
+         (module-metadata (meta-go-import->module-meta meta-go-import)))
+    (close-port port)
+    module-metadata))
+
+(define (module-meta-data-repo-url meta-data goproxy-url)
+  "Return the URL where the fetcher which will be used can download the source
+control."
+  (if (member (module-meta-vcs meta-data)'(fossil mod))
+      goproxy-url
+      (module-meta-repo-root meta-data)))
+
+(define (vcs->origin vcs-type vcs-repo-url version file)
+  "Generate the `origin' block of a package depending on what type of source
+control system is being used."
+  (case vcs-type
+    ((git)
+     `(origin
+        (method git-fetch)
+        (uri (git-reference
+              (url ,vcs-repo-url)
+              (commit (go-version->git-ref version))))
+        (file-name (git-file-name name version))
+        (sha256
+         (base32
+           ;; FIXME: get hash for git repo checkout
+           "0000000000000000000000000000000000000000000000000000"))))
+    ((hg)
+     `(origin
+        (method hg-fetch)
+        (uri (hg-reference
+              (url ,vcs-repo-url)
+              (changeset ,version)))
+        (file-name (format #f "~a-~a-checkout" name version))))
+    ((svn)
+     `(origin
+        (method svn-fetch)
+        (uri (svn-reference
+              (url ,vcs-repo-url)
+              (revision (string->number version))
+              (recursive? #f)))
+        (file-name (format #f "~a-~a-checkout" name version))
+        (sha256
+         (base32
+          ,(guix-hash-url file)))))
+    (else
+     (raise-exception (format #f "unsupported vcs type: ~a" vcs-type)))))
+
+(define* (go-module->guix-package module-path #:key (goproxy-url "https://proxy.golang.org"))
+  (call-with-temporary-output-file
+   (lambda (temp port)
+     (let* ((latest-version (go-module-latest-version* goproxy-url module-path))
+            (go.mod-path (fetch-go.mod goproxy-url module-path latest-version
+                                       temp))
+            (dependencies (map car (parse-go.mod temp)))
+            (guix-name (go-module->guix-package-name module-path))
+            (root-module-path (infer-module-root-repo module-path))
+            ;; VCS type and URL are not included in goproxy information. For
+            ;; this we need to fetch it from the official module page.
+            (meta-data (fetch-module-meta-data root-module-path))
+            (vcs-type (module-meta-vcs meta-data))
+            (vcs-repo-url (module-meta-data-repo-url meta-data goproxy-url)))
+       (values
+        `(package
+           (name ,guix-name)
+           ;; Elide the "v" prefix Go uses
+           (version ,(string-trim latest-version #\v))
+           (source
+            ,(vcs->origin vcs-type vcs-repo-url latest-version temp))
+           (build-system go-build-system)
+           (arguments
+            '(#:import-path ,root-module-path))
+           ,@(maybe-inputs (map go-module->guix-package-name dependencies))
+           ;; TODO(katco): It would be nice to make an effort to fetch this
+           ;; from known forges, e.g. GitHub
+           (home-page ,(format #f "https://~a" root-module-path))
+           (synopsis "A Go package")
+           (description ,(format #f "~a is a Go package." guix-name))
+           (license #f))
+        dependencies)))))
+
+(define go-module->guix-package* (memoize go-module->guix-package))
+
+(define* (go-module-recursive-import package-name
+                                     #:key (goproxy-url "https://proxy.golang.org"))
+  (recursive-import
+   package-name
+   #:repo->guix-package (lambda* (name . _)
+                          (go-module->guix-package*
+                           name
+                           #:goproxy-url goproxy-url))
+   #:guix-name go-module->guix-package-name))
diff --git a/guix/scripts/import.scm b/guix/scripts/import.scm
index 0a3863f965..1d2b45d942 100644
--- a/guix/scripts/import.scm
+++ b/guix/scripts/import.scm
@@ -77,7 +77,7 @@ rather than \\n."
 ;;;
 
 (define importers '("gnu" "nix" "pypi" "cpan" "hackage" "stackage" "elpa" "gem"
-                    "cran" "crate" "texlive" "json" "opam"))
+                    "go" "cran" "crate" "texlive" "json" "opam"))
 
 (define (resolve-importer name)
   (let ((module (resolve-interface
diff --git a/guix/scripts/import/go.scm b/guix/scripts/import/go.scm
new file mode 100644
index 0000000000..fde7555973
--- /dev/null
+++ b/guix/scripts/import/go.scm
@@ -0,0 +1,118 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2020 Katherine Cox-Buday <cox.katherine.e@gmail.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 scripts import go)
+  #:use-module (guix ui)
+  #:use-module (guix utils)
+  #:use-module (guix scripts)
+  #:use-module (guix import go)
+  #:use-module (guix scripts import)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-11)
+  #:use-module (srfi srfi-37)
+  #:use-module (ice-9 match)
+  #:use-module (ice-9 format)
+  #:export (guix-import-go))
+
+
+;;;
+;;; Command-line options.
+;;;
+
+(define %default-options
+  '())
+
+(define (show-help)
+  (display (G_ "Usage: guix import go PACKAGE-PATH
+Import and convert the Go module for PACKAGE-PATH.\n"))
+  (display (G_ "
+  -h, --help             display this help and exit"))
+  (display (G_ "
+  -V, --version          display version information and exit"))
+  (display (G_ "
+  -r, --recursive        generate package expressions for all Go modules\
+ that are not yet in Guix"))
+  (display (G_ "
+  -p, --goproxy=GOPROXY  specify which goproxy server to use"))
+  (newline)
+  (show-bug-report-information))
+
+(define %options
+  ;; Specification of the command-line options.
+  (cons* (option '(#\h "help") #f #f
+                 (lambda args
+                   (show-help)
+                   (exit 0)))
+         (option '(#\V "version") #f #f
+                 (lambda args
+                   (show-version-and-exit "guix import go")))
+         (option '(#\r "recursive") #f #f
+                 (lambda (opt name arg result)
+                   (alist-cons 'recursive #t result)))
+         (option '(#\p "goproxy") #t #f
+                 (lambda (opt name arg result)
+                   (alist-cons 'goproxy
+                               (string->symbol arg)
+                               (alist-delete 'goproxy result))))
+         %standard-import-options))
+
+
+;;;
+;;; Entry point.
+;;;
+
+(define (guix-import-go . args)
+  (define (parse-options)
+    ;; Return the alist of option values.
+    (args-fold* args %options
+                (lambda (opt name arg result)
+                  (leave (G_ "~A: unrecognized option~%") name))
+                (lambda (arg result)
+                  (alist-cons 'argument arg result))
+                %default-options))
+
+  (let* ((opts (parse-options))
+         (args (filter-map (match-lambda
+                             (('argument . value)
+                              value)
+                             (_ #f))
+                           (reverse opts))))
+    (match args
+      ((module-name)
+       (if (assoc-ref opts 'recursive)
+           (map (match-lambda
+                  ((and ('package ('name name) . rest) pkg)
+                   `(define-public ,(string->symbol name)
+                      ,pkg))
+                  (_ #f))
+                (go-module-recursive-import module-name
+                                            #:goproxy-url
+                                            (or (assoc-ref opts 'goproxy)
+                                                "https://proxy.golang.org")))
+           (let ((sexp (go-module->guix-package module-name
+                                                #:goproxy-url
+                                                (or (assoc-ref opts 'goproxy)
+                                                    "https://proxy.golang.org"))))
+             (unless sexp
+               (leave (G_ "failed to download meta-data for module '~a'~%")
+                      module-name))
+             sexp)))
+      (()
+       (leave (G_ "too few arguments~%")))
+      ((many ...)
+       (leave (G_ "too many arguments~%"))))))
diff --git a/guix/self.scm b/guix/self.scm
index 35fba1152d..ed5ee9ddea 100644
--- a/guix/self.scm
+++ b/guix/self.scm
@@ -814,6 +814,9 @@ itself."
   (define guile-ssh
     (specification->package "guile-ssh"))
 
+  (define guile-lib
+    (specification->package "guile-lib"))
+
   (define guile-git
     (specification->package "guile-git"))
 
@@ -842,7 +845,7 @@ itself."
     (append-map transitive-package-dependencies
                 (list guile-gcrypt gnutls guile-git guile-avahi
                       guile-json guile-semver guile-ssh guile-sqlite3
-                      guile-zlib guile-lzlib guile-zstd)))
+                      guile-lib guile-zlib guile-lzlib guile-zstd)))
 
   (define *core-modules*
     (scheme-node "guix-core"
diff --git a/tests/import-go.scm b/tests/import-go.scm
new file mode 100644
index 0000000000..ad4185684c
--- /dev/null
+++ b/tests/import-go.scm
@@ -0,0 +1,144 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2021 François Joulaud <francois.joulaud@radiofrance.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/>.
+
+;;; Summary
+;; Tests for guix/import/go.scm
+
+(define-module (test-import-go)
+  #:use-module (guix import go)
+  #:use-module (guix base32)
+  #:use-module (ice-9 iconv)
+  #:use-module (ice-9 match)
+  #:use-module (srfi srfi-64))
+
+(define fixture-go-mod-simple
+  "module my/thing
+go 1.12
+require other/thing v1.0.2
+require new/thing/v2 v2.3.4
+exclude old/thing v1.2.3
+replace bad/thing v1.4.5 => good/thing v1.4.5
+")
+
+(define fixture-go-mod-with-block
+  "module M
+
+require (
+         A v1
+         B v1.0.0
+         C v1.0.0
+         D v1.2.3
+         E dev
+)
+
+exclude D v1.2.3
+")
+
+
+(define fixture-go-mod-complete
+  "module M
+
+go 1.13
+
+replace github.com/myname/myproject/myapi => ./api
+
+replace github.com/mymname/myproject/thissdk => ../sdk
+
+replace launchpad.net/gocheck => github.com/go-check/check v0.0.0-20140225173054-eb6ee6f84d0a
+
+require (
+	github.com/user/project v1.1.11
+	github.com/user/project/sub/directory v1.1.12
+	bitbucket.org/user/project v1.11.20
+	bitbucket.org/user/project/sub/directory v1.11.21
+	launchpad.net/project v1.1.13
+	launchpad.net/project/series v1.1.14
+	launchpad.net/project/series/sub/directory v1.1.15
+	launchpad.net/~user/project/branch v1.1.16
+	launchpad.net/~user/project/branch/sub/directory v1.1.17
+	hub.jazz.net/git/user/project v1.1.18
+	hub.jazz.net/git/user/project/sub/directory v1.1.19
+	k8s.io/kubernetes/subproject v1.1.101
+	one.example.com/abitrary/repo v1.1.111
+	two.example.com/abitrary/repo v0.0.2
+	\"quoted.example.com/abitrary/repo\" v0.0.2
+)
+
+replace two.example.com/abitrary/repo => github.com/corp/arbitrary-repo v0.0.2
+
+replace (
+	golang.org/x/sys => golang.org/x/sys v0.0.0-20190813064441-fde4db37ae7a // pinned to release-branch.go1.13
+	golang.org/x/tools => golang.org/x/tools v0.0.0-20190821162956-65e3620a7ae7 // pinned to release-branch.go1.13
+)
+
+")
+
+(test-begin "import go")
+
+(test-equal "go-path-escape"
+  "github.com/!azure/!avere"
+  ((@@ (guix import go) go-path-escape) "github.com/Azure/Avere"))
+
+
+
+;; We define a function for all similar tests with different go.mod files
+(define (testing-parse-mod name expected input)
+  (define (inf? p1 p2)
+    (string<? (car p1) (car p2)))
+  (let ((input-port (open-input-string input)))
+    (test-equal name
+      (sort expected inf?)
+      (sort
+       ( (@@ (guix import go) parse-go.mod-port)
+         input-port)
+       inf?))))
+
+(testing-parse-mod "parse-go.mod-simple"
+                   '(("good/thing" . "v1.4.5")
+                     ("new/thing/v2" . "v2.3.4")
+                     ("other/thing" . "v1.0.2"))
+                   fixture-go-mod-simple)
+
+(testing-parse-mod "parse-go.mod-with-block"
+                   '(("A" . "v1")
+                     ("B" . "v1.0.0")
+                     ("C" . "v1.0.0")
+                     ("D" . "v1.2.3")
+                     ("E" . "dev"))
+                   fixture-go-mod-with-block)
+
+(testing-parse-mod "parse-go.mod-complete"
+                   '(("github.com/corp/arbitrary-repo" . "v0.0.2")
+                     ("quoted.example.com/abitrary/repo" . "v0.0.2")
+                     ("one.example.com/abitrary/repo" . "v1.1.111")
+                     ("hub.jazz.net/git/user/project/sub/directory" . "v1.1.19")
+                     ("hub.jazz.net/git/user/project" . "v1.1.18")
+                     ("launchpad.net/~user/project/branch/sub/directory" . "v1.1.17")
+                     ("launchpad.net/~user/project/branch" . "v1.1.16")
+                     ("launchpad.net/project/series/sub/directory" . "v1.1.15")
+                     ("launchpad.net/project/series" . "v1.1.14")
+                     ("launchpad.net/project" . "v1.1.13")
+                     ("bitbucket.org/user/project/sub/directory" . "v1.11.21")
+                     ("bitbucket.org/user/project" . "v1.11.20")
+                     ("k8s.io/kubernetes/subproject" . "v1.1.101")
+                     ("github.com/user/project/sub/directory" . "v1.1.12")
+                     ("github.com/user/project" . "v1.1.11")
+                     ("github.com/go-check/check" . "v0.0.0-20140225173054-eb6ee6f84d0a"))
+                   fixture-go-mod-complete)
+
+(test-end "import go")
-- 
2.28.0