Workspace status?

[Dan Fabulich]

I need to incorporate git hash and build timestamp in my build output. https://github.com/bazelbuild/bazel/issues/216 seems relevant, but I don't understand it.

What is "workspace status"? How does it work? How can I feed workspace status information into my build outputs?

[Brian Silverman]

For the git part, you set --workspace_status_command to a script which retrieves the information, and then Bazel can feed that information into build targets. tools/buildstamp/get_workspace_status in the Bazel source tree is a good example of retrieving the git hash, and Bazel supplies the timestamp automatically.

Retrieving the values is rule-specific. The rule types I've done that with are cc_library and genrule. You can set the linkstamp attribute of a cc_library to a .cc file which will have BUILD_SCM_REVISION and BUILD_TIMESTAMP defined to the appropriate values when it's compiled. For a genrule, if you set the stamp attribute to 1 it will be able to access bazel-out/volatile-status.txt which has the information. I've seen Bazel code for doing something with a .properties file for Java code, but I've never actually figured out how to use it.

On Wed, Mar 16, 2016 at 7:55 PM, Dan Fabulich <danfa...@gmail.com> wrote:

I need to incorporate git hash and build timestamp in my build output. https://github.com/bazelbuild/bazel/issues/216 seems relevant, but I don't understand it.

What is "workspace status"? How does it work? How can I feed workspace status information into my build outputs?

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[Dan Fabulich]

http://bazel.io/docs/be/general.html#genrule doesn't say anything about "stamp." Is it documented somewhere? (Indeed, the documentation there says, "Do ensure that tools run by a genrule are deterministic and hermetic. They should not write timestamps to their output")

Does this mean users would have to launch bazel with "bazel build --workspace_status_command=status.py //:foo" every time they run it? Is there a way to check in a file that automatically specifies a workspace status command?

How could I access volatile-status.txt in a Skylark action?

[Brian Silverman]

Yea, it's not documented... Rule with stamping are handled specially by Bazel to do the dependencies correctly.

You can write "build --workspace_status_command=./status.py" (FYI, the ./ is important) in a tools/bazel.rc to do it automatically.

I don't think there's currently a way to get at it directly from a Skylark action, but that would be useful.

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