Bazel Query Examples¶

This guide demonstrates how to use bazel query and bazel aquery to explore the build graph.

Basic Queries¶

List all targets in the workspace¶

bazel query //...

Output:

//go_service:go_service_test
//go_service:server
//py_service:py_service_test
//py_service:server
//tests:test_go_service
//tests:test_py_service

List targets in a specific package¶

bazel query //go_service:all

Find all test targets¶

bazel query 'kind(test, //...)'

Find all Python targets¶

bazel query 'kind(py_.*, //...)'

Find all Go targets¶

bazel query 'kind(go_.*, //...)'

Dependency Queries¶

Show all dependencies of a target¶

bazel query 'deps(//go_service:server)'

This shows everything the Go server depends on, including: - Source files - Toolchains - External dependencies

Show only direct dependencies¶

bazel query 'deps(//go_service:server, 1)'

The 1 limits the depth to immediate dependencies only.

Find what depends on a target (reverse dependencies)¶

bazel query 'rdeps(//..., //go_service:server)'

This shows all targets that depend on the Go server.

Show path between two targets¶

bazel query 'somepath(//py_service:server, @pip_deps//:fastapi)'

Visualization¶

Generate a dependency graph¶

bazel query 'deps(//go_service:server)' --output=graph > go_deps.dot

Then convert to image (requires Graphviz):

dot -Tpng go_deps.dot -o go_deps.png

Generate graph for entire workspace¶

bazel query '//...' --output=graph > workspace.dot
dot -Tpng workspace.dot -o workspace.png

Action Queries (Advanced)¶

aquery shows the actual actions (compile, link, etc.) that Bazel executes.

Show all actions for building a target¶

bazel aquery //go_service:server

Show only compilation actions¶

bazel aquery 'mnemonic("GoCompile", //go_service:server)'

Show linking actions¶

bazel aquery 'mnemonic("GoLink", //go_service:server)'

Show actions with inputs and outputs¶

bazel aquery //go_service:server --output=text

Practical Examples¶

Find all binary targets (runnable services)¶

bazel query 'kind(".*_binary", //...)'

Output:

//go_service:server
//py_service:server

Find targets that changed since last commit¶

bazel query --universe_scope=//... \
  --order_output=no \
  "set(//...)" --output=label

Check if target exists¶

bazel query //py_service:server &>/dev/null && echo "Target exists" || echo "Target not found"

Find unused dependencies (requires analysis)¶

# This is more complex and requires additional tooling
bazel query "rdeps(//..., //some:target, 1)" --output=label_kind

Filtering and Formatting¶

Output as a list¶

bazel query '//...' --output=label

Output as JSON¶

bazel query '//...' --output=jsonproto

Output with kind (target type)¶

bazel query '//...' --output=label_kind

Example output:

go_binary rule //go_service:server
py_binary rule //py_service:server
go_test rule //go_service:go_service_test
py_test rule //py_service:py_service_test

Query Functions Cheatsheet¶

Function	Description	Example
`deps(target)`	All dependencies	`deps(//go_service:server)`
`rdeps(universe, target)`	Reverse dependencies	`rdeps(//..., //py_service:server)`
`allpaths(from, to)`	All paths between targets	`allpaths(//go_service:server, @rules_go//:go)`
`somepath(from, to)`	One path between targets	`somepath(//go_service:server, @rules_go//:go)`
`kind(pattern, input)`	Filter by target type	`kind(test, //...)`
`attr(name, pattern, input)`	Filter by attribute	`attr(srcs, ".*\.py", //...)`
`labels(attr, input)`	Extract label values	`labels(srcs, //go_service:server)`
`filter(pattern, input)`	Filter labels by regex	`filter("test", //...)`

Performance Tips¶

Use `--universe_scope` for large queries¶

bazel query 'allpaths(//service:a, //service:b)' --universe_scope=//service/...

This limits the search space, making queries faster.

Use `--nohost_deps` to skip host dependencies¶

bazel query 'deps(//go_service:server)' --nohost_deps

Use `--notool_deps` to skip tool dependencies¶

bazel query 'deps(//go_service:server)' --notool_deps

Debugging Build Issues¶

Find why a target is built¶

bazel query 'rdeps(//..., //some:target)' --output=graph | dot -Tpng > why_built.png

Check for circular dependencies¶

bazel query 'somepath(//pkg:target, //pkg:target)'
# If output is found, there's a cycle

List all external dependencies¶

bazel query 'kind("http_archive", @*//...)'