Full minimal reproduction repro with a running github action at: https://github.com/samhowes/rules_go_runfiles_repro
Failing github action run: https://github.com/samhowes/rules_go_runfiles_repro/runs/2370880759?check_suite_focus=true
Output of interest: Error: panic: error parsing runfiles manifest: C:/users/runneradmin/_bazel_runneradmin/t32zp6hb/execroot/__main__/bazel-out/x64_windows-opt-exec-2B5CBBC6/bin/parent.exe.runfiles/MANIFEST:1: no space

Sample manifest that reproduces this issue: https://github.com/samhowes/rules_go_runfiles_repro/blob/main/sample_MANIFEST

Target producing the output: //:parent_output_test

What version of rules_go are you using?

1.16

What version of gazelle are you using?

v0.23.0

What version of Bazel are you using?

Build label: 4.0.0
Build target: bazel-out/x64_windows-opt/bin/src/main/java/com/google/devtools/build/lib/bazel/BazelServer_deploy.jar
Build time: Thu Jan 21 07:39:16 2021 (1611214756)
Build timestamp: 1611214756
Build timestamp as int: 1611214756

Does this issue reproduce with the latest releases of all the above?

The above are the latest releases

What operating system and processor architecture are you using?

windows x64

Any other potentially useful information about your toolchain?

its all standard

What did you do?

I made a py_binary target that has a data dependency on a go_binary target then tried to execute the go_binary from within the py_binary. Inside of the go_binary I tried to execute path, err := bazel.Runfile("important.txt") to access a runfile that the go_binary has as a data dependency.

On windows.

What did you expect to see?

No err, and a successful location of the runfile.

What did you see instead?

error parsing runfiles manifest: C:/users/runneradmin/_bazel_runneradmin/t32zp6hb/execroot/__main__/bazel-out/x64_windows-opt-exec-2B5CBBC6/bin/parent.exe.runfiles/MANIFEST:1: no space