Metrics

bca metrics computes per-file metrics and emits them either to stdout or to a directory of structured files.

Migrating? This command replaces the pre-restructure --metrics flag. The aggregated report previously selected with -O markdown now lives under bca report, and the CI/IDE offender formats (Checkstyle, SARIF, code-climate, clang-warning, msvc-warning) moved to bca check --output-format <fmt>. See the migration guide.

Display metrics

To compute and display metrics for a given file or directory, run:

bca --paths /path/to/your/file/or/directory metrics

• --paths (or -p): file or directory to analyze. If a directory is provided, metrics are computed for every supported file it contains.

Exporting metrics

bca metrics supports five per-file output formats:

• CBOR
• CSV
• JSON
• TOML
• YAML

Both JSON and TOML can be exported as pretty-printed.

The three top-level output kinds map to three separate commands so each one stays consistent with its data model:

The CI/IDE offender formats (Checkstyle, SARIF, code-climate, clang-warning, msvc-warning) used to live on bca metrics -O <fmt>. They moved to bca check --output-format <fmt> in #235 because their input is a list of threshold violations, not the per-file metric tree that the other formats above carry. See the bca check chapter for the new invocation.

Export command

To export metrics as JSON files:

bca --paths /path/to/your/file/or/directory metrics \
    -O json -o /path/to/output/directory

• -O, --output-format: per-file output format (cbor, csv, json, toml, yaml).
• -o, --output: directory to save output files. Filenames mirror the input file plus the format extension. If omitted, results are printed to stdout. CBOR is binary and therefore requires -o.

CSV (spreadsheets and Pandas)

bca --paths /path/to/your/code metrics \
    -O csv -o csv-output

The CSV writer emits one row per FuncSpace (function, class, struct, unit, etc.) with the entire metric matrix as columns. Header order is fixed — see CSV_HEADER in src/output/csv.rs for the canonical list. Identity columns come first (path, space_name, space_kind, start_line, end_line) followed by every leaf metric using the same dotted JSON-style names (loc.lloc, halstead.volume, cyclomatic.modified.average, etc.) so a single column name addresses the metric in both CSV and JSON.

Empty cells (no value, not 0) signal "not applicable for this space" — for example, the OOP-only metrics (wmc.*, npm.*, npa.*) appear empty for procedural code. RFC 4180 quoting is delegated to the [csv] crate, so paths and names containing commas, quotes, or newlines round-trip cleanly.

Stream the result to a single file with -:

bca --paths /path/to/your/code metrics -O csv \
    > metrics.csv

CSV is a per-file format; with --output <dir> each input file produces a <input>.csv mirror under the output directory.

An aggregated HTML report covering the whole walk is available via bca report html. The previous per-file bca metrics -O html writer was removed because it degraded to an unopenable single-file table on real-world repos — CSV is the right shape for flat per-FuncSpace rows.

Pretty print

bca --paths /path/to/your/file/or/directory metrics \
    --pretty -O json

Excluding inline test code

bca --paths /path/to/your/code --exclude-tests metrics

By default, every node in the AST is counted, including inline test items. Rust files following the idiomatic #[cfg(test)] mod tests { ... } layout therefore have headline metrics that mix production and test code together.

Pass --exclude-tests to elide test-only subtrees before any metric is computed. The flag is recognised by every subcommand that walks the AST (metrics, report, check), and currently understands the following Rust attribute shapes:

• #[test] and #[rstest] / #[test_case] / #[wasm_bindgen_test]
• #[cfg(test)], #[cfg(all(test, ...))], #[cfg(any(test, ...))]
• #[tokio::test], #[async_std::test], #[test_log::test], … (any path ending in ::test)
• #![cfg(test)] on mod items (inner attribute form)

Languages without a Checker::should_skip_subtree override simply ignore the flag — only Rust applies the pruning today. The default remains off so existing metric numbers stay byte-identical for users who do not opt in.

Aggregated report

For a comprehensive, human-readable quality report, use bca report markdown. That command aggregates metrics across all analyzed files and produces per-language hotspot tables.

Listing available metrics

Tooling that drives the CLI can discover the metric catalog at runtime instead of hard-coding it:

bca list-metrics

prints metric names one per line. Pass descriptions for a one-line summary of each metric:

bca list-metrics descriptions