Advanced target selection

Alternative techniques to tell Pants which files/targets to run on.

See Goal arguments for the normal techniques for telling Pants what to
run on.

See Project introspection for queries that you can run and then pipe
into another Pants run, such as finding the dependencies of a target or file.

Running over changed files with --changed-since

Because Pants understands Git, it can find which files have changed since a certain commit through the --changed-since option.

For example, to lint all uncommitted files, run:

./pants --changed-since=HEAD lint

To run against another branch, run:

./pants --changed-since=origin/main lint

By default, --changed-since will only run over files directly changed. Often, though, you will want to run over any dependees of those changed files, meaning any targets that depend on the changed files. Use --changed-dependees=direct or --changed-dependees=transitive for this:

❯ ./pants \
  --changed-since=origin/main \
  --changed-dependees=transitive \
  test

filter options

Use filters to operate on only targets that match the predicate, e.g. only running Python tests.

Specify a predicate by using one of the below filter options, like --filter-target-type. You
can use a comma to OR multiple values, meaning that at least one member must be matched. You
can repeat the option multiple times to AND each filter. You can prefix the filter with
- to negate the filter, meaning that the target must not be true for the filter.

Some examples:

# Only `python_source` targets.
./pants --filter-target-type=python_source list ::

# `python_source` or `python_test` targets.
./pants --filter-target-type='python_source,python_test' list ::

# Any target except for `python_source` targets
./pants --filter-target-type='-python_source' list ::

You can combine multiple filter options in the same run, e.g.:

./pants --filter-target-type='python_test' --filter-address-regex=^integration_tests test ::

--filter-target-type

Each value should be the name of a target type, e.g.
./pants --filter-target-type=python_test test ::.

Run ./pants help targets to see what targets are registered.

--filter-address-regex

Regex strings for the address, such as
./pants --filter-address-regex='^integration_tests$' test ::.

--filter-tag-regex

Regex strings to match against the tags field, such as
./pants --filter-tag-regex='^skip_lint$' lint ::.

If you don't need the power of regex, use the simpler --tag global option explained below.

Tags: annotating targets

Every target type has a field called tags, which allows you to add a sequence of strings. The
strings can be whatever you'd like, such as "integration_test".

python_tests(
    name="integration",
    sources=["*_integration_test.py"],
    tags=["skip_lint", "integration_test"],
)

You can then filter by tags with the global --tag option, like this:

./pants --tag=integration_test list ::

To exclude certain tags, prefix with a -:

./pants --tag='-integration_test' list ::

You can even combine multiple includes and excludes:

./pants --tag='+type_checked,skip_lint' --tag='-integration_test' list ::

Use --filter-tag-regex instead for more complex queries.

--spec-files

The global option --spec-files allows you to pass a file containing target addresses and/or file names/globs to Pants.

Each entry must be separated by a new line.

For example:

$ ./pants --spec-files=targets.txt list
helloworld/lang/*.py
helloworld/util
helloworld/util:tests

📘

Tip: centralized allow/block lists

Whereas tags are useful for decentralized allow/block lists, --spec-files is useful when you want to define one single list of targets or files.

Piping to other Pants runs

To pipe a Pants run, use your shell's | pipe operator and xargs:

./pants dependees helloworld/util | xargs ./pants  list

You can, of course, pipe multiple times:

# Run over the second-degree dependees of `utils.py`.
❯ ./pants dependees helloworld/utils.py | \
   xargs ./pants dependees | \
   xargs ./pants lint

📘

Alternative: use --spec-files

Sometimes, you may want to reuse the output of a Pants run for multiple subsequent Pants runs. Rather than repeating xargs multiple times, you can generate a file through stdout redirection and --spec-files.

For example:

$ ./pants dependencies helloworld/util > util_dependencies.txt
$ ./pants --spec-files=util_dependencies.txt lint

If you don't want to save the output to an actual file—such as to not pollute version control—you can use a variable and a named pipe:

$ TARGETS=$(./pants dependencies helloworld/util)
$ ./pants --spec-files=<(echo $TARGETS) lint

Sharding the input targets

The test goal natively supports sharding input targets into multiple shards. Use the option --test-shard=k/N, where k is a non-negative integer less than N. For example, you can split up your CI into three shards with --shard=0/3, --shard=1/3, and --shard=2/3.

For other goals, you can leverage shell piping to partition the input targets into multiple shards. For example, to split your package run into 5 shards, and select shard 0:

./pants list :: | awk 'NR % 5 == 0' | xargs ./pants package

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