can no longer use include_prefix = "" in cc_library with Bazel 6.0.0

[carpenterjc]

Description of the bug:

We use include_prefix in our C++ assets for legacy component laytout. This has stopped working in bazel 6.0.0, although the virtual includes directory is produced.

If you use include_prefix = "x" and #include "x/blah.h" it works.
If you use includes = ["."] and #include "blah.h" it works.
If you use include_prefix = "" and #include "blah.h" it fails.

What's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.

diff --git a/.bazelversion b/.bazelversion
new file mode 100644
index 0000000..73fcd45
--- /dev/null
+++ b/.bazelversion
@@ -0,0 +1 @@
+6.0.0rc5
\ No newline at end of file
diff --git a/BUILD b/BUILD
new file mode 100644
index 0000000..ff015f9
--- /dev/null
+++ b/BUILD
@@ -0,0 +1,5 @@
+cc_test(
+    name="test",
+    srcs = ["test.cpp"],
+    deps = ["//blah"],
+)
\ No newline at end of file
diff --git a/WORKSPACE b/WORKSPACE
new file mode 100644
index 0000000..e69de29
diff --git a/blah/BUILD b/blah/BUILD
new file mode 100644
index 0000000..08a2dd6
--- /dev/null
+++ b/blah/BUILD
@@ -0,0 +1,6 @@
+cc_library(
+    name = "blah",
+    hdrs = ["blah.h"],
+    include_prefix = "",
+    visibility = ["//:__pkg__"],
+)
diff --git a/blah/blah.h b/blah/blah.h
new file mode 100644
index 0000000..e69de29
diff --git a/test.cpp b/test.cpp
new file mode 100644
index 0000000..6dc850a
--- /dev/null
+++ b/test.cpp
@@ -0,0 +1,5 @@
+#include "blah.h"
+
+int main(){
+    return 0;
+}
\ No newline at end of file

Which operating system are you running Bazel on?

windows

What is the output of bazel info release?

release 6.0.0rc5

If bazel info release returns development version or (@non-git), tell us how you built Bazel.

No response

What's the output of git remote get-url origin; git rev-parse master; git rev-parse HEAD ?

No response

Have you found anything relevant by searching the web?

No response

Any other information, logs, or outputs that you want to share?

Bazel 6.0.0 output fails...

ERROR: C:/dev/test/BUILD:1:8: Compiling test.cpp failed: (Exit 2): cl.exe failed: error executing command (from target //:test)
  cd /d C:/dev/_bazel/l2habeez/execroot/__main__
  SET INCLUDE=C:\bazeltools\vs16\VC\Tools\MSVC\14.29.30133\ATLMFC\include;C:\bazeltools\vs16\VC\Tools\MSVC\14.29.30133\include;C:\Program Files (x86)\Windows Kits\NETFXSDK\4.8\include\um;C:\Program Files (x86)\Windows Kits\10\include\10.0.22000.0\ucrt;C:\Program Files (x86)\Windows Kits\10\include\10.0.22000.0\shared;C:\Program Files (x86)\Windows Kits\10\include\10.0.22000.0\um;C:\Program Files (x86)\Windows Kits\10\include\10.0.22000.0\winrt;C:\Program Files (x86)\Windows Kits\10\include\10.0.22000.0\cppwinrt
    SET PATH=C:\bazeltools\vs16\VC\Tools\MSVC\14.29.30133\bin\HostX64\x64;C:\bazeltools\vs16\Common7\IDE\VC\VCPackages;C:\bazeltools\vs16\Common7\IDE\CommonExtensions\Microsoft\TestWindow;C:\bazeltools\vs16\Common7\IDE\CommonExtensions\Microsoft\TeamFoundation\Team Explorer;C:\bazeltools\vs16\MSBuild\Current\bin\Roslyn;C:\Program Files (x86)\Microsoft SDKs\Windows\v10.0A\bin\NETFX 4.8 Tools\x64\;C:\bazeltools\vs16\Common7\Tools\devinit;C:\Program Files (x86)\Windows Kits\10\bin\10.0.22000.0\x64;C:\Program Files (x86)\Windows Kits\10\bin\x64;C:\bazeltools\vs16\\MSBuild\Current\Bin;C:\Windows\Microsoft.NET\Framework64\v4.0.30319;C:\bazeltools\vs16\Common7\IDE\;C:\bazeltools\vs16\Common7\Tools\;;C:\Windows\system32
    SET PWD=/proc/self/cwd
    SET RUNFILES_MANIFEST_ONLY=1
    SET TEMP=C:\Users\JAMESC~1\AppData\Local\Temp
    SET TMP=C:\Users\JAMESC~1\AppData\Local\Temp
  C:\bazeltools\vs16\VC\Tools\MSVC\14.29.30133\bin\HostX64\x64\cl.exe /nologo /DCOMPILER_MSVC /DNOMINMAX /D_WIN32_WINNT=0x0601 /D_CRT_SECURE_NO_DEPRECATE /D_CRT_SECURE_NO_WARNINGS /bigobj /Zm500 /EHsc /wd4351 /wd4291 /wd4250 /wd4996 /I. /Ibazel-out/x64_windows-fastbuild/bin /Iexternal/bazel_tools /Ibazel-out/x64_windows-fastbuild/bin/external/bazel_tools /DBAZEL_CURRENT_REPOSITORY="" /showIncludes /MD /Od /Z7 /wd4117 -D__DATE__="redacted" -D__TIMESTAMP__="redacted" -D__TIME__="redacted" /Fobazel-out/x64_windows-fastbuild/bin/_objs/test/test.obj /c test.cpp
# Configuration: b67f5ac3d5b94ed15e96cb37e833e7120042529b3e382867f55890fe82af9163
# Execution platform: @local_config_platform//:host
test.cpp(1): fatal error C1083: Cannot open include file: 'blah.h': No such file or directory
INFO: Elapsed time: 1.060s, Critical Path: 0.14s
INFO: 2 processes: 2 internal.                                                                                                                                                                                                               
FAILED: Build did NOT complete successfully

Working with Bazel 5.3.2

PS C:\dev\test> bazel build ... -s                
Starting local Bazel server and connecting to it...
INFO: Invocation ID: 1a9c33cb-a9f5-4155-8b4b-d7a3931a6f13
INFO: Analyzed 2 targets (48 packages loaded, 681 targets configured).
INFO: Found 2 targets...
SUBCOMMAND: # //:test [action 'Compiling test.cpp', configuration: 8fcc02caf7268a43edcd2a5a3e8e4edfa3c614a84823ca1599fcd30251ebce9f, execution platform: @local_config_platform//:host]
cd /d C:/dev/_bazel/l2habeez/execroot/__main__
  SET INCLUDE=C:\bazeltools\vs16\VC\Tools\MSVC\14.29.30133\ATLMFC\include;C:\bazeltools\vs16\VC\Tools\MSVC\14.29.30133\include;C:\Program Files (x86)\Windows Kits\NETFXSDK\4.8\include\um;C:\Program Files (x86)\Windows Kits\10\include\10.0.22000.0\ucrt;C:\Program Files (x86)\Windows Kits\10\include\10.0.22000.0\shared;C:\Program Files (x86)\Windows Kits\10\include\10.0.22000.0\um;C:\Program Files (x86)\Windows Kits\10\include\10.0.22000.0\winrt;C:\Program Files (x86)\Windows Kits\10\include\10.0.22000.0\cppwinrt
    SET PATH=C:\bazeltools\vs16\VC\Tools\MSVC\14.29.30133\bin\HostX64\x64;C:\bazeltools\vs16\Common7\IDE\VC\VCPackages;C:\bazeltools\vs16\Common7\IDE\CommonExtensions\Microsoft\TestWindow;C:\bazeltools\vs16\Common7\IDE\CommonExtensions\Microsoft\TeamFoundation\Team Explorer;C:\bazeltools\vs16\MSBuild\Current\bin\Roslyn;C:\Program Files (x86)\Microsoft SDKs\Windows\v10.0A\bin\NETFX 4.8 Tools\x64\;C:\bazeltools\vs16\Common7\Tools\devinit;C:\Program Files (x86)\Windows Kits\10\bin\10.0.22000.0\x64;C:\Program Files (x86)\Windows Kits\10\bin\x64;C:\bazeltools\vs16\\MSBuild\Current\Bin;C:\Windows\Microsoft.NET\Framework64\v4.0.30319;C:\bazeltools\vs16\Common7\IDE\;C:\bazeltools\vs16\Common7\Tools\;;C:\Windows\system32
    SET PWD=/proc/self/cwd
    SET RUNFILES_MANIFEST_ONLY=1
    SET TEMP=C:\Users\JAMESC~1\AppData\Local\Temp
    SET TMP=C:\Users\JAMESC~1\AppData\Local\Temp
  C:\bazeltools\vs16\VC\Tools\MSVC\14.29.30133\bin\HostX64\x64\cl.exe /nologo /DCOMPILER_MSVC /DNOMINMAX /D_WIN32_WINNT=0x0601 /D_CRT_SECURE_NO_DEPRECATE /D_CRT_SECURE_NO_WARNINGS /bigobj /Zm500 /EHsc /wd4351 /wd4291 /wd4250 /wd4996 /I. /Ibazel-out/x64_windows-fastbuild/bin /Iexternal/bazel_tools /Ibazel-out/x64_windows-fastbuild/bin/external/bazel_tools /Ibazel-out/x64_windows-fastbuild/bin/blah/_virtual_includes/blah /showIncludes /MD /Od /Z7 /wd4117 -D__DATE__="redacted" -D__TIMESTAMP__="redacted" -D__TIME__="redacted" /Fobazel-out/x64_windows-fastbuild/bin/_objs/test/test.obj /c test.cpp
# Configuration: 8fcc02caf7268a43edcd2a5a3e8e4edfa3c614a84823ca1599fcd30251ebce9f
# Execution platform: @local_config_platform//:host
INFO: Elapsed time: 15.772s, Critical Path: 0.11s
INFO: 2 processes: 1 disk cache hit, 1 internal.
INFO: Build completed successfully, 2 total actions

Virtual includes are created, but don't seem to work.

PS C:\dev\test> dir .\bazel-bin\ -r | select -exp fullname
C:\dev\test\bazel-bin\blah
C:\dev\test\bazel-bin\test.exe.runfiles
C:\dev\test\bazel-bin\_objs
C:\dev\test\bazel-bin\test.exe
C:\dev\test\bazel-bin\test.exe-2.params
C:\dev\test\bazel-bin\test.exe.runfiles_manifest
C:\dev\test\bazel-bin\test.pdb
C:\dev\test\bazel-bin\blah\_virtual_includes
C:\dev\test\bazel-bin\blah\_virtual_includes\blah
C:\dev\test\bazel-bin\blah\_virtual_includes\blah\blah.h
C:\dev\test\bazel-bin\test.exe.runfiles\MANIFEST
C:\dev\test\bazel-bin\_objs\test

[fmeum]

@bazel-io flag

[fmeum]

cc_common.compile interprets include_prefix = "" as if it wasn't set (ref), whereas Java CcLibrary checks whether the attribute has been set explicitly (ref), which Starlark can't emulate without wrapper macros distinguishing between None and "" (#14434). strip_include_prefix is affected by this logic as well and this is not limited to Windows.

[fmeum]

@carpenterjc Could you check whether making the following programmatic change is sufficient to resolve the build failure in your real-world repo?

buildozer 'substitute include_prefix ^$ .' //...:%cc_library
buildozer 'substitute strip_include_prefix ^$ .' //...:%cc_library

If that's the extent of the migration required, having it be a minor incompatible change may be better than carrying the subtle "" vs. None issue forward.

[carpenterjc]

Yes, so if have include_prefix = "." then it also works.

[carpenterjc]

Will you get the edge case where the _virtual_includes directory is created with include_prefix = "" but that is not actually usable.

[fmeum]

@oquenchil

[meteorcloudy]

/cc @buildbreaker2021 , can you please take a look? My current assessment is that this is probably a minor incompatible change with workarounds, so probably shouldn't block the 6.0 release. If there is something we should fix, we can cherry pick it into 6.1. WDYT?

[buildbreaker2021]

I agree with Fabian here and I do not see the reason to add more tech debt to fix this. Like adding a hack in cc_library to change "" to ".", for example. The buildozer workaround described here is simple enough.
Also "." is more explicit than "" IMO.