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• Copyright (c) Meta Platforms, Inc. and affiliates.
• This source code is licensed under the MIT license found in the
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Pyrefly Coverage

pyrefly coverage measures how much of your code is annotated with types. It has two subcommands:

• pyrefly coverage check fails when coverage is below a threshold, useful as a CI gate.
• pyrefly coverage report emits a JSON report with per-module statistics.

:::warning Experimental The output format and behavior may change in future releases without notice. :::

How coverage is measured

Coverage is counted over typables: function return types, function parameters, module-level variables, and class attributes. Each typable is either typed (annotated, no Any in the resolved type), any (annotated, but the resolved type contains Any), or untyped (no annotation).

• Coverage is the percentage of typables that are annotated; Any counts as covered.
• Strict coverage is the percentage of typables that are typed; Any doesn't count.

Only public symbols count: names without a leading underscore, plus anything in __all__. self/cls are not typable, overloads are merged, and .py files are skipped when their .pyi stub is also analyzed (--prefer-stubs=false disables this). With --public-only, only symbols reachable from public modules via re-export chains count: the library's public API.

Checking coverage against a threshold

pyrefly coverage check robot/ --fail-under 60

On success it prints a one-line summary and exits 0:

 INFO type coverage 66.67% (4 of 6 typable)

Otherwise it exits non-zero and reports every offending symbol in the same style as pyrefly check, as coverage-missing (no annotations at all) or coverage-partial (only some):

 WARN `walk` is not fully typed [coverage-partial]
 --> robot/legs.py:1:1
  |
1 | / def walk(speed, direction: str) -> None:
2 | |     print(f"walking {speed} {direction}")
  | |_________________________________________-
  |
 WARN `stop` is untyped [coverage-missing]
 --> robot/legs.py:5:1
  |
5 | / def stop():
6 | |     print("stopping")
  | |_____________________-
  |
ERROR type coverage 66.67% (4 of 6 typable) is below the 100.00% threshold

With --strict, annotations that resolve to Any count as untyped. The findings format is configurable with --output-format. See pyrefly coverage check --help for all flags.

Generating a JSON report

pyrefly coverage report path/to/directory/ > coverage.json

The report contains a "major.minor" schema_version, a summary, and one entry per module in module_reports, with:

• per-symbol typed/any/untyped counts and locations (symbol_reports)
• the module's public names (names)
• error-suppression comments (type_ignores)
• typable totals, coverage and strict_coverage percentages, and counts of functions, methods, parameters, classes, attributes, and properties

See pyrefly coverage report --help for all flags. The output is easy to consume with e.g. jq:

pyrefly coverage report path/to/directory/ | jq .summary.strict_coverage