Merge 'master' into core-updates

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diff --git a/guix/build/go-build-system.scm b/guix/build/go-build-system.scm
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+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2016 Petter <petter@mykolab.ch>
+;;; Copyright © 2017 Leo Famulari <leo@famulari.name>
+;;;
+;;; 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 build go-build-system)
+  #:use-module ((guix build gnu-build-system) #:prefix gnu:)
+  #:use-module (guix build utils)
+  #:use-module (ice-9 match)
+  #:use-module (srfi srfi-1)
+  #:export (%standard-phases
+            go-build))
+
+;; Commentary:
+;;
+;; Build procedures for Go packages.  This is the builder-side code.
+;;
+;; Software written in Go is either a 'package' (i.e. library) or 'command'
+;; (i.e. executable).  Both types can be built with either the `go build` or `go
+;; install` commands.  However, `go build` discards the result of the build
+;; process for Go libraries, so we use `go install`, which preserves the
+;; results. [0]
+
+;; Go software is developed and built within a particular filesystem hierarchy
+;; structure called a 'workspace' [1].  This workspace is found by Go
+;; via the GOPATH environment variable.  Typically, all Go source code
+;; and compiled objects are kept in a single workspace, but it is
+;; possible for GOPATH to contain a list of directories, and that is
+;; what we do in this go-build-system. [2]
+;;
+;; Go software, whether a package or a command, is uniquely named using
+;; an 'import path'.  The import path is based on the URL of the
+;; software's source.  Since most source code is provided over the
+;; internet, the import path is typically a combination of the remote
+;; URL and the source repository's filesystem structure. For example,
+;; the Go port of the common `du` command is hosted on github.com, at
+;; <https://github.com/calmh/du>.  Thus, the import path is
+;; <github.com/calmh/du>. [3]
+;;
+;; It may be possible to programatically guess a package's import path
+;; based on the source URL, but we don't try that in this revision of
+;; the go-build-system.
+;;
+;; Modules of modular Go libraries are named uniquely with their
+;; filesystem paths.  For example, the supplemental but "standardized"
+;; libraries developed by the Go upstream developers are available at
+;; <https://golang.org/x/{net,text,crypto, et cetera}>.  The Go IPv4
+;; library's import path is <golang.org/x/net/ipv4>.  The source of
+;; such modular libraries must be unpacked at the top-level of the
+;; filesystem structure of the library.  So the IPv4 library should be
+;; unpacked to <golang.org/x/net>.  This is handled in the
+;; go-build-system with the optional #:unpack-path key.
+;;
+;; In general, Go software is built using a standardized build mechanism
+;; that does not require any build scripts like Makefiles.  This means
+;; that all modules of modular libraries cannot be built with a single
+;; command.  Each module must be built individually.  This complicates
+;; certain cases, and these issues are currently resolved by creating a
+;; filesystem union of the required modules of such libraries.  I think
+;; this could be improved in future revisions of the go-build-system.
+;;
+;; [0] `go build`:
+;; https://golang.org/cmd/go/#hdr-Compile_packages_and_dependencies
+;; `go install`:
+;; https://golang.org/cmd/go/#hdr-Compile_and_install_packages_and_dependencies
+;; [1] Go workspace example, from <https://golang.org/doc/code.html#Workspaces>:
+;; bin/
+;;     hello                          # command executable
+;;     outyet                         # command executable
+;; pkg/
+;;     linux_amd64/
+;;         github.com/golang/example/
+;;             stringutil.a           # package object
+;; src/
+;;     github.com/golang/example/
+;;         .git/                      # Git repository metadata
+;; 	   hello/
+;; 	       hello.go               # command source
+;; 	   outyet/
+;; 	        main.go               # command source
+;; 	        main_test.go          # test source
+;; 	   stringutil/
+;; 	       reverse.go             # package source
+;; 	       reverse_test.go        # test source
+;;         golang.org/x/image/
+;;             .git/                  # Git repository metadata
+;; 	       bmp/
+;; 	           reader.go          # package source
+;; 	           writer.go          # package source
+;;     ... (many more repositories and packages omitted) ...
+;;
+;; [2] https://golang.org/doc/code.html#GOPATH
+;; [3] https://golang.org/doc/code.html#ImportPaths
+;;
+;; Code:
+
+(define* (unpack #:key source import-path unpack-path #:allow-other-keys)
+  "Unpack SOURCE in the UNPACK-PATH, or the IMPORT-PATH is the UNPACK-PATH is
+unset.  When SOURCE is a directory, copy it instead of unpacking."
+  (if (string-null? import-path)
+      ((display "WARNING: The Go import path is unset.\n")))
+  (if (string-null? unpack-path)
+      (set! unpack-path import-path))
+  (mkdir "src")
+  (let ((dest (string-append "src/" unpack-path)))
+    (mkdir-p dest)
+    (if (file-is-directory? source)
+      (begin
+        (copy-recursively source dest #:keep-mtime? #t)
+        #t)
+      (if (string-suffix? ".zip" source)
+        (zero? (system* "unzip" "-d" dest source))
+        (zero? (system* "tar" "-C" dest "-xvf" source))))))
+
+(define* (install-source #:key outputs #:allow-other-keys)
+  "Install the source code to the output directory."
+  (let* ((out (assoc-ref outputs "out"))
+         (source "src")
+         (dest (string-append out "/" source)))
+    (copy-recursively source dest #:keep-mtime? #t)
+    #t))
+
+(define (go-package? name)
+  (string-prefix? "go-" name))
+
+(define (go-inputs inputs)
+  "Return the alist of INPUTS that are Go software."
+  ;; XXX This should not check the file name of the store item. Instead we
+  ;; should pass, from the host side, the list of inputs that are packages using
+  ;; the go-build-system.
+  (alist-delete "go" ; Exclude the Go compiler
+    (alist-delete "source" ; Exclude the source code of the package being built
+      (filter (match-lambda
+                ((label . directory)
+                 (go-package? ((compose package-name->name+version
+                                        strip-store-file-name)
+                               directory)))
+                (_ #f))
+              inputs))))
+
+(define* (setup-environment #:key inputs outputs #:allow-other-keys)
+  "Export the variables GOPATH and GOBIN, which are based on INPUTS and OUTPUTS,
+respectively."
+  (let ((out (assoc-ref outputs "out")))
+    ;; GOPATH is where Go looks for the source code of the build's dependencies.
+    (set-path-environment-variable "GOPATH"
+                                   ;; XXX Matching "." hints that we could do
+                                   ;; something simpler here...
+                                   (list ".")
+                                   (match (go-inputs inputs)
+                                     (((_ . dir) ...)
+                                      dir)))
+
+    ;; Add the source code of the package being built to GOPATH.
+    (if (getenv "GOPATH")
+      (setenv "GOPATH" (string-append (getcwd) ":" (getenv "GOPATH")))
+      (setenv "GOPATH" (getcwd)))
+    ;; Where to install compiled executable files ('commands' in Go parlance').
+    (setenv "GOBIN" out)
+    #t))
+
+(define* (build #:key import-path #:allow-other-keys)
+  "Build the package named by IMPORT-PATH."
+  (or
+    (zero? (system* "go" "install"
+                    "-v" ; print the name of packages as they are compiled
+                    "-x" ; print each command as it is invoked
+                    import-path))
+    (begin
+      (display (string-append "Building '" import-path "' failed.\n"
+                              "Here are the results of `go env`:\n"))
+      (system* "go" "env")
+      #f)))
+
+(define* (check #:key tests? import-path #:allow-other-keys)
+  "Run the tests for the package named by IMPORT-PATH."
+  (if tests?
+    (zero? (system* "go" "test" import-path))))
+
+(define* (install #:key outputs #:allow-other-keys)
+  "Install the compiled libraries. `go install` installs these files to
+$GOPATH/pkg, so we have to copy them into the output direcotry manually.
+Compiled executable files should have already been installed to the store based
+on $GOBIN in the build phase."
+  (when (file-exists? "pkg")
+    (copy-recursively "pkg" (string-append (assoc-ref outputs "out") "/pkg")))
+  #t)
+
+(define %standard-phases
+  (modify-phases gnu:%standard-phases
+    (delete 'configure)
+    (delete 'patch-generated-file-shebangs)
+    (replace 'unpack unpack)
+    (add-after 'unpack 'install-source install-source)
+    (add-before 'build 'setup-environment setup-environment)
+    (replace 'build build)
+    (replace 'check check)
+    (replace 'install install)))
+
+(define* (go-build #:key inputs (phases %standard-phases)
+                      #:allow-other-keys #:rest args)
+  "Build the given Go package, applying all of PHASES in order."
+  (apply gnu:gnu-build #:inputs inputs #:phases phases args))