From bf6362aa01dd00c82996dcabfb1cb20d7919c552 Mon Sep 17 00:00:00 2001
From: Lorenz Brun <lorenz@nexantic.com>
Date: Wed, 22 Jul 2020 09:46:56 +0200
Subject: [PATCH] Add support for prepatching

---
 internal/go_repository.bzl | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/internal/go_repository.bzl b/internal/go_repository.bzl
index 9928fa8..a3af13d 100644
--- a/internal/go_repository.bzl
+++ b/internal/go_repository.bzl
@@ -213,6 +213,8 @@ def _go_repository_impl(ctx):
         if ctx.attr.debug_mode and result.stderr:
             print("fetch_repo: " + result.stderr)
 
+    patch(ctx, True)
+
     # Repositories are fetched. Determine if build file generation is needed.
     build_file_names = ctx.attr.build_file_name.split(",")
     existing_build_file = ""
@@ -474,6 +476,10 @@ go_repository = repository_rule(
             Gazelle directives.""",
         ),
 
+        # Patches to apply before running gazelle.
+        "pre_patches": attr.label_list(),
+        "pre_patch_cmds": attr.string_list(default = []),
+
         # Patches to apply after running gazelle.
         "patches": attr.label_list(
             doc = "A list of patches to apply to the repository after gazelle runs.",
@@ -504,10 +510,11 @@ go_repository = repository_rule(
 """See repository.md#go-repository for full documentation."""
 
 # Copied from @bazel_tools//tools/build_defs/repo:utils.bzl
-def patch(ctx):
+def patch(ctx, pre_mode = False):
     """Implementation of patching an already extracted repository"""
     bash_exe = ctx.os.environ["BAZEL_SH"] if "BAZEL_SH" in ctx.os.environ else "bash"
-    for patchfile in ctx.attr.patches:
+    patches = ctx.attr.patches if not pre_mode else ctx.attr.pre_patches
+    for patchfile in patches:
         command = "{patchtool} {patch_args} < {patchfile}".format(
             patchtool = ctx.attr.patch_tool,
             patchfile = ctx.path(patchfile),
@@ -520,7 +527,8 @@ def patch(ctx):
         if st.return_code:
             fail("Error applying patch %s:\n%s%s" %
                  (str(patchfile), st.stderr, st.stdout))
-    for cmd in ctx.attr.patch_cmds:
+    patch_cmds = ctx.attr.patch_cmds if not pre_mode else ctx.attr.pre_patch_cmds
+    for cmd in patch_cmds:
         st = ctx.execute([bash_exe, "-c", cmd])
         if st.return_code:
             fail("Error applying patch command %s:\n%s%s" %
-- 
2.25.1