Windows: Java rules require MSYS

[laszlocsomor]

Description of the problem / feature request:

The Java rules depend on at least on genrule, so they need MSYS on Windows.

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

On a fresh Windows 10:

1. download Bazel 0.18.0
2. install the MSVC redistributable DLLs
3. download and install JDK 8
4. create a fake msys script as c:\src\tmp\fake-msys\usr\bin\bash.bat that just prints its arguments and exits:

C:\src\tmp>notepad c:\src\tmp\fake-msys\usr\bin\bash.bat

C:\src\tmp>type c:\src\tmp\fake-msys\usr\bin\bash.bat
@echo OFF
echo Fake MSYS, args=(%0 %1 %2 %3 ...)
exit /B 1

5. Create a workspace with one BUILD rule and one Java file:

C:\src\tmp>type BUILD
java_binary(
  name = "hello_java",
  srcs = ["Hello.java"],
  main_class = "Hello",
)

C:\src\tmp>type Hello.java
public class Hello {
  public static void main(String[] args) {
    System.out.println("hello Java!");
  }
}

6. in cmd.exe:

C:\src\tmp>set BAZEL_SH=c:\src\tmp\fake-msys\usr\bin\bash.bat

C:\src\tmp>bazel build //:hello_java
...
ERROR: 
C:/users/laszlocsomor/_bazel_laszlocsomor/zovul4l7/external/bazel_tools/tools/jdk/BUILD:202:5: Executing genrule @bazel_tools//tools/jdk:platformclasspath8 failed (Exit 1)
Fake MSYS, args=("C:\src\tmp\fake-msys\usr\bin\bash.bat" -c "source external/bazel_tools/tools/genrule/genrule-setup.sh;  ...)
Target //:hello_java failed to build

The same thing happens even when JAVA_HOME is set.

What operating system are you running Bazel on?

Windows Server 2016 (v1607)

[cushon]

@bazel_tools//tools/jdk:platformclasspath8 isn't genrule at head, fwiw.

[laszlocsomor]

Thanks! Indeed, using Bazel built from HEAD, I can make this work -- I replaced my fake Bash with an .exe file I wrote that just prints its arguments and exits 1, then I put it under c:\src\fake-msys\usr\bin\bash.exe, pointed BAZEL_SH at it, and could successfully build the java_binary in the bug report.

[laszlocsomor]

See also #6475