Review the dependency graph

A successful build has all of its dependencies explicitly stated in the BUILD file. Bazel uses those statements to create the project’s dependency graph, which enables accurate incremental builds.

To visualize the sample project’s dependencies, you can generate a text representation of the dependency graph by running this command at the workspace root:

bazel query --notool_deps --noimplicit_deps "deps(//main:hello-world)" \
  --output graph

The above command tells Bazel to look for all dependencies for the target //main:hello-world (excluding host and implicit dependencies) and format the output as a graph.

Then, paste the text into GraphViz.

On Ubuntu, you can view the graph locally by installing GraphViz and the xdot Dot Viewer:

sudo apt update && sudo apt install graphviz xdot

Then you can generate and view the graph by piping the text output above straight to xdot:

xdot <(bazel query --notool_deps --noimplicit_deps "deps(//main:hello-world)" \
  --output graph)

As you can see, the first stage of the sample project has a single target that builds a single source file with no additional dependencies:

Figure 1. Dependency graph for hello-world displays a single target with a single source file.

After you set up your workspace, build your project, and examine its dependencies, then you can add some complexity.