go_test: change directory before use init() functions run

[dragonsinth]

Fixes #1918 go_test: data not available in init()

What type of PR is this?

Bug fix

What does this PR do? Why is it needed?

Forces a new package, go/tools/test_init to have its package initializer run before any Go user code can be initialized. This package sets the correct working directory, PWD, and TMPDIR to match bazel standards.

Which issues(s) does this PR fix?

Fixes #1918

[dragonsinth]

Looks like I have some things to fix!

[jayconrod]

Thanks for working on this. Couple comments below.

[jayconrod]

This should only be an implicit dependency of go_test.

coverdata is a little different, because every go_library might need to import it. test_init only needs to be imported by go_test archives.

[dragonsinth]

Sorry for being so dense, but how do I do that exactly? I tried doing that first, but I could never figure out exactly how and where to add this dep without following the coverdata pattern. I can try hacking at this more and give more detail on exactly what I ran into.

[jayconrod]

_testmain_additional_srcs is a better pattern to follow. Add an attribute to go_test that starts with _. It should be an attr.label with a default value pointing to that go_library target.

[dragonsinth]

I think I'm close, but I'm missing something. I added this:

--- a/go/private/rules/test.bzl
+++ b/go/private/rules/test.bzl
@@ -137,12 +137,14 @@ def _go_test_impl(ctx):
         resolve = None,
     )
     test_deps = external_archive.direct + [external_archive]
-    test_deps.append(go.test_init)
+    print("test_deps[0]:", type(test_deps[0]), test_deps[0])
+    print("_testmain_additional_deps[0]:", type(ctx.files._testmain_additional_deps[0]), ctx.files._testmain_additional_deps[0])
+    print("go.coverdata:", type(go.coverdata), go.coverdata)
     if ctx.configuration.coverage_enabled:
         test_deps.append(go.coverdata)
     test_source = go.library_to_source(go, struct(
         srcs = [struct(files = [main_go] + ctx.files._testmain_additional_srcs)],
-        deps = test_deps,
+        deps = test_deps + ctx.files._testmain_additional_deps,
     ), test_library, False)
     test_archive, executable, runfiles = go.binary(
         go,
@@ -201,6 +203,10 @@ _go_test_kwargs = {
             default = ["@io_bazel_rules_go//go/tools/testwrapper:srcs"],
             allow_files = go_exts,
         ),
+        "_testmain_additional_deps": attr.label_list(
+            providers = [GoLibrary],
+            default = ["@io_bazel_rules_go//go/tools/testinit"],
+        ),
         # Workaround for bazelbuild/bazel#6293. See comment in lcov_merger.sh.
         "_lcov_merger": attr.label(
             executable = True,

But the thing is, when I get to the print statements, the _testmain_additional_deps[0] is a File, whereas go.coverdata is a struct. I can't figure out how to make it be the kind of thing it needs to be. :/

[dragonsinth]

Resolved all the feedback except for this-- I'm a little out of my depth. :(

[dragonsinth]

Alright.. I finally stumbled my way through this! I needed ctx.attr._testmain_additional_deps to get the actual target, not ctx.files._testmain_additional_deps which only has the output file. Big oof!

[dragonsinth]

@jayconrod does this repo not run correctly under OSX? I'm sorry to be asking such an off topic question, but I can't get things to build on my machine due to '@local_config_cc//:toolchain' does not contain a toolchain for cpu 'darwin_x86_64'. I've reinstalled xcode command line tools, bazel clean expunge, bazel sync, and nothing I've tried lets me get this running locally. (This is on master, not even on my branch.)

[jayconrod]

It should work on macOS. I do most of my development there.

Sounds like a C/C++ toolchain configuration problem? Are you able to build a cc_binary? Not sure I can help much there.

[dragonsinth]

Sounds like a C/C++ toolchain configuration problem? Are you able to build a cc_binary? Not sure I can help much there.

I was able to get past this-- the problem is only with tests/core/cgo/objc:objc_test. I just commented it out locally and everything else builds fine.

[dragonsinth]

All feedback should now be addressed.

[jayconrod]

Looks good. Thanks again for working on this!

[dragonsinth]

Sweet! Funny enough, I was meaning to add test coverage as well. So I went ahead and opened a new PR.