From f42e4ebb56fe4f16991ca6c6e060c8f3535865cb Mon Sep 17 00:00:00 2001
From: Maxim Cournoyer <maxim.cournoyer@gmail.com>
Date: Fri, 5 Apr 2019 00:00:08 -0400
Subject: [PATCH] build: go-build-system: Ensure uniform unpacking directory.

Depending on whether the source is a directory or an archive, we strip the
source directory or preserve it, respectively.  This change makes it so that
whether the type of the source, it is unpacked at the expected location given
by the IMPORT-PATH of the Go build system.

* guix/build/go-build-system.scm: Add the (ice-9 ftw) module.
(unpack): Add inner procedure to maybe strip the top level directory of an
archive, document it and use it.
---
 guix/build/go-build-system.scm | 36 +++++++++++++++++++++++++---------
 1 file changed, 27 insertions(+), 9 deletions(-)

diff --git a/guix/build/go-build-system.scm b/guix/build/go-build-system.scm
index 92a5c86d6c..d106e70d35 100644
--- a/guix/build/go-build-system.scm
+++ b/guix/build/go-build-system.scm
@@ -1,6 +1,7 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2016 Petter <petter@mykolab.ch>
 ;;; Copyright © 2017, 2019 Leo Famulari <leo@famulari.name>
+;;; Copyright © 2019 Maxim Cournoyer <maxim.cournoyer@gmail.com>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -22,6 +23,7 @@ (define-module (guix build go-build-system)
   #:use-module (guix build union)
   #:use-module (guix build utils)
   #:use-module (ice-9 match)
+  #:use-module (ice-9 ftw)
   #:use-module (srfi srfi-1)
   #:use-module (rnrs io ports)
   #:use-module (rnrs bytevectors)
@@ -151,13 +153,31 @@ (define* (setup-go-environment #:key inputs outputs #:allow-other-keys)
   #t)
 
 (define* (unpack #:key source import-path unpack-path #:allow-other-keys)
-  "Relative to $GOPATH, 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
+  "Relative to $GOPATH, unpack SOURCE in UNPACK-PATH, or IMPORT-PATH when
+UNPACK-PATH is unset.  If the SOURCE archive has a single top level directory,
+it is stripped so that the sources appear directly under UNPACK-PATH.  When
+SOURCE is a directory, copy its content into UNPACK-PATH 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))
+  (define (unpack-maybe-strip source dest)
+    (let* ((scratch-dir (string-append (or (getenv "TMPDIR") "/tmp")
+                                       "/scratch-dir"))
+           (out (mkdir-p scratch-dir)))
+      (with-directory-excursion scratch-dir
+        (if (string-suffix? ".zip" source)
+            (invoke "unzip" source)
+            (invoke "tar" "-xvf" source))
+        (let ((top-level-files (remove (lambda (x)
+                                         (member x '("." "..")))
+                                       (scandir "."))))
+          (match top-level-files
+            ((top-level-file)
+             (when (file-is-directory? top-level-file)
+               (copy-recursively top-level-file dest #:keep-mtime? #t)))
+            (_
+             (copy-recursively "." dest #:keep-mtime? #t)))
+          #t))
+      (delete-file-recursively scratch-dir)))
+
   (when (string-null? import-path)
     ((display "WARNING: The Go import path is unset.\n")))
   (when (string-null? unpack-path)
@@ -168,9 +188,7 @@ (define* (unpack #:key source import-path unpack-path #:allow-other-keys)
         (begin
           (copy-recursively source dest #:keep-mtime? #t)
           #t)
-        (if (string-suffix? ".zip" source)
-            (invoke "unzip" "-d" dest source)
-            (invoke "tar" "-C" dest "-xvf" source)))))
+        (unpack-maybe-strip source dest))))
 
 (define (go-package? name)
   (string-prefix? "go-" name))