From a60f5974e0d9807805f91ca17d5b8b55634a27cb Mon Sep 17 00:00:00 2001
From: Martin Medler <medler.martin@gmail.com>
Date: Mon, 15 Jan 2024 21:43:00 +0100
Subject: [PATCH] Make aspect MSVC compatible

---
 src/aspect/dwyu.bzl           | 7 +++++--
 src/aspect/test/dwyu_test.bzl | 7 +++++++
 test/aspect/defines/BUILD     | 6 +++++-
 3 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/src/aspect/dwyu.bzl b/src/aspect/dwyu.bzl
index 02c51560..9ad56245 100644
--- a/src/aspect/dwyu.bzl
+++ b/src/aspect/dwyu.bzl
@@ -76,12 +76,15 @@ def extract_defines_from_compiler_flags(compiler_flags):
     defines = {}
 
     for cflag in compiler_flags:
-        if cflag.startswith("-U"):
+        # gcc/clang use '-U'. MSVC uses '/U'.
+        if cflag.startswith(("-U", "/U")):
             undefine = cflag[2:]
             undefine_name = undefine.split("=", 1)[0]
             if undefine_name in defines.keys():
                 defines.pop(undefine_name)
-        if cflag.startswith("-D"):
+
+        # gcc/clang use '-D'. MSVC uses '/D'.
+        if cflag.startswith(("-D", "/D")):
             define = cflag[2:]
             define_name = define.split("=", 1)[0]
             defines[define_name] = define
diff --git a/src/aspect/test/dwyu_test.bzl b/src/aspect/test/dwyu_test.bzl
index 885568bd..a2de10cf 100644
--- a/src/aspect/test/dwyu_test.bzl
+++ b/src/aspect/test/dwyu_test.bzl
@@ -29,6 +29,13 @@ def _extract_defines_from_compiler_flags_test_impl(ctx):
         extract_defines_from_compiler_flags(["-DFoo=BAR=42", "-DTick 42", '-DRiff "Raff"']),
     )
 
+    # MSVC syntax
+    asserts.equals(
+        env,
+        ["Bar", "FooBar=42"],
+        extract_defines_from_compiler_flags(["/DFoo", "/UFoo", "/DBar", "/DFooBar=42"]),
+    )
+
     return unittest.end(env)
 
 extract_defines_from_compiler_flags_test = unittest.make(_extract_defines_from_compiler_flags_test_impl)
diff --git a/test/aspect/defines/BUILD b/test/aspect/defines/BUILD
index 92cff0aa..2a60ed62 100644
--- a/test/aspect/defines/BUILD
+++ b/test/aspect/defines/BUILD
@@ -7,7 +7,11 @@ cc_library(
 cc_library(
     name = "defines_from_bazel_target",
     hdrs = ["defines_from_bazel_target.h"],
-    copts = ["-DSOME_COPT 42"],
+    copts = select({
+        # Strictly speaking Windows does not automatically equal MSVC, but does so in our integration tests
+        "@platforms//os:windows": ["/DSOME_COPT 42"],
+        "//conditions:default": ["-DSOME_COPT 42"],
+    }),
     defines = ["SOME_DEFINE"],
     local_defines = ["LOCAL_DEFINE"],
     deps = ["//defines/support:lib_a"],