Bazel has a feature that lets you see a graph of your build dependencies. It could help you debug things, but honestly it’s just really cool to see what your build is doing.
To try it out, you’ll need a project that uses Bazel to build. If you don’t have one handy, here’s a tiny workspace you can use:
$ git clone https://github.com/kchodorow/tiny-workspace.git $ cd tiny-workspace
Now run bazel query in your tiny-workspace/ directory, asking it to search for all dependencies of //:main and format the output as a graph:
$ bazel query 'deps(//:main)' --output graph > graph.in
This creates a file called graph.in, which is a text representation of the build graph. You can use dot (install with sudo apt-get install graphviz
) to create a png from this:
$ dot -Tpng graph.png
If you open up graph.png, you should see something like this:
You can see //:main depends on one file (//:main.cc) and four targets (//:x, //tools/cpp:stl, //tools/default:crosstool, and //tools/cpp:malloc). All of the //tools targets are implicit dependencies of any C++ target: every C++ build you do needs the right compiler, flags, and libraries available, but it crowds your result graph. You can exclude these implicit dependencies by removing them from your query results:
$ bazel query --noimplicit_deps 'deps(//:main)' --output graph > simplified_graph.in
Now the resulting graph is just:
Much neater!
If you’re interested in further refining your query, check out the docs on querying.
I think, but not sure, that “query –package_path %workspace%:[path to bazel]/base_workspace” is no longer needed. If I’m correct I think it would be helpful to update the post for noobs dropping in (maybe to the repost in bazel blog as well). Thanks for your amazing work!
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Quite so! Thank you!
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The pictures are expired and some of the commands in this web page are missing chunks:
dot -Tpng graph.in > graph.png
dot -Tpng simplified_graph.in > simplified_graph.png
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