buildGoPackage: check/delete vendor

doc/languages-frameworks/go.xml

@@ -117,7 +117,9 @@ deis = buildGoPackage rec {
 
   goDeps = ./deps.nix; <co xml:id='ex-buildGoPackage-3' />
 
-  buildFlags = [ "--tags" "release" ]; <co xml:id='ex-buildGoPackage-4' />
+  deleteVendor = true; <co xml:id='ex-buildGoPackage-4' />
+
+  buildFlags = [ "--tags" "release" ]; <co xml:id='ex-buildGoPackage-5' />
 }
 </programlisting>
   </example>
@@ -144,6 +146,11 @@ deis = buildGoPackage rec {
      </para>
     </callout>
     <callout arearefs='ex-buildGoPackage-4'>
+     <para>
+      <varname>deleteVendor</varname> removes the pre-existing vendor directory. This should only be used if the dependencies included in the vendor folder are broken or incomplete.
+     </para>
+    </callout>
+    <callout arearefs='ex-buildGoPackage-5'>
      <para>
       <varname>buildFlags</varname> is a list of flags passed to the go build command.
      </para>

pkgs/development/go-packages/generic/default.nix

@@ -29,6 +29,9 @@
 # go2nix dependency file
 , goDeps ? null
 
+# Whether to delete the vendor folder supplied with the source.
+, deleteVendor ? false
+
 , dontRenameImports ? false
 
 # Do not enable this without good reason
@@ -96,6 +99,18 @@ let
       mkdir -p "go/src/$(dirname "$goPackagePath")"
       mv "$sourceRoot" "go/src/$goPackagePath"
 
+    '' + lib.optionalString (deleteVendor == true) ''
+      if [ ! -d "go/src/$goPackagePath/vendor" ]; then
+        echo "vendor folder does not exist, 'deleteVendor' is not needed"
+        exit 10
+      else
+        rm -rf "go/src/$goPackagePath/vendor"
+      fi
+    '' + lib.optionalString (goDeps != null) ''
+      if [ -d "go/src/$goPackagePath/vendor" ]; then
+        echo "vendor folder exists, 'goDeps' is not needed"
+        exit 10
+      fi
     '' + lib.flip lib.concatMapStrings goPath ({ src, goPackagePath }: ''
       mkdir goPath
       (cd goPath; unpackFile "${src}")