scb-check 0.1.3

CLI for measuring verbosity and erosion metrics in Python codebases

scb-check

Python CLI that reports SCBench verbosity and erosion composites for a Python codebase.

• Paper

• Source

• SlopCodeBench (main repo)

• Verbosity: fraction of SLOC flagged by clone detection, ast-grep slop rules, or trivial-wrapper detection.

• Erosion: share of function "mass" (complexity * sqrt(sloc)) concentrated in high-complexity functions (cyclomatic complexity > 10).

• Cognitive erosion: same mass-share calculation using cognitive complexity > 10.

Install

Requires Python 3.12+.

Run without installing (recommended):

uvx scb-check check PATH
uvx --from git+https://github.com/gabeorlanski/scb-check scb-check check PATH

Or install into the current project:

uv sync              # for development in this repo
uv add scb-check     # as a dependency elsewhere

For hash-checked dependency installs from this repository, use the exported lock files:

python -m pip install --require-hashes -r requirements.lock
python -m pip install --require-hashes -r requirements-dev.lock

Regenerate them after dependency changes with:

uv export --format requirements.txt --no-dev --no-emit-project --frozen --output-file requirements.lock
uv export --format requirements.txt --all-groups --no-emit-project --frozen --output-file requirements-dev.lock

Usage

scb-check check PATH                    # human-readable flags
scb-check check PATH --output-format json  # JSON report with verbosity/erosion scores
scb-check check PATH --report           # shortcut for --output-format json
scb-check check PATH -v / --verbosity   # add info logging
scb-check check PATH -vv                # add debug logging
scb-check check PATH --config FILE      # explicit config path
scb-check check PATH --include-all      # include ignored and boundary-suppressed ast-grep findings
scb-check check PATH --disable-sg  # skip ast-grep subprocess findings
scb-check check PATH --min-duplicate-lines N  # show duplicate groups with at least N SLOC lines
scb-check rule RULE_ID                  # print YAML for a specific ast-grep rule

PATH may be a file or directory. Directories are walked for *.py files.

JSON report fields

verbosity, erosion, cog_erosion, files_scanned, total_loc, verbosity_flagged_loc, clone_loc, ast_grep_flagged_loc, trivial_wrapper_loc, trivial_wrappers, total_functions, high_cc_functions, high_cog_functions, total_mass, high_cc_mass, total_cog_mass, high_cog_mass.

Configuration

scb-check looks for scb-check.toml or a pyproject.toml containing [tool.scb-check], [tool.ruff], or [tool.ty.src], walking upward from the current directory until it hits a .git root.

# scb-check.toml
exclude = ["tests/fixtures/*", "vendor/**"]
context = 1

# pyproject.toml
[tool.scb-check]
exclude = ["tests/fixtures/*"]
context = 2

• exclude: list of glob patterns to skip while discovering Python files.
• context: number of surrounding source lines to show around human-readable ast-grep, trivial-wrapper, and erosion findings.

When using pyproject.toml, scb-check also includes excludes from:

• [tool.ruff].exclude
• [tool.ruff].extend-exclude
• [tool.ty.src].exclude

Source directives

You can suppress specific ast-grep or trivial-wrapper findings at the source line level with:

# scbc ignore[rule-id]
# scbc ignore[trivial-wrapper]

Same-line form:

value = cfg.get("a", {}).get("b", {})  # scbc ignore[chained-dict-get] Boundary normalization for legacy webhook payloads.

Standalone block form:

# scbc ignore[chained-dict-get]
# Boundary normalization for legacy webhook payloads.
value = cfg.get("a", {}).get("b", {})

Multiple rule IDs:

# scbc ignore[chained-dict-get,dict-get-empty-dict-default]
# Legacy webhook payloads are partially populated and normalized downstream.
value = cfg.get("a", {}).get("b", {})

Function-level boundary suppression is available for code that intentionally validates or normalizes external input:

def _load_toml(path: Path) -> dict[str, Any]:
    # scbc boundary: reads and validates user config
    ...

Boundary directives must be inside the function body, after the def line. By default, ast-grep findings inside that function are hidden. Use --include-all to show ignored and boundary-suppressed ast-grep findings.

Rules:

• Rule IDs inside ignore[...] are required.
• Reason text is optional.
• Same-line ignore directives apply to that same physical line.
• Standalone ignore directives apply to the next non-blank, non-comment code line.
• Boundary directives apply to the containing function body.
• Ast-grep and trivial-wrapper findings are suppressible; clone and erosion findings are not.
• Invalid directives fail the run with exit code 2 unless --include-all is used.

How it works

• Parsing: tree-sitter-python.
• Clone detection: hashed AST blocks across the scanned set; two or more matching instances become a CloneBlock.
• Slop patterns: ast-grep rules in src/scb_check/resources/slop_rules/ split by category (e.g. range(len(x)), dict.get(k, None), isinstance ladders, manual min/max, defensive guards).
• Trivial wrappers: tree-sitter detects functions whose only executable body statement is return ..., plus aliases to functions defined in scanned files. Findings include resolved usage locations within the scanned files.
• Extra local slop patterns: set SCB_CHECK_EXTRA_SLOP_RULES to a :-separated list of YAML paths to layer additional rules on top of the bundled set.
• Complexity: per-function cyclomatic and cognitive complexity plus SLOC, combined into mass scores for erosion metrics.

Development

uv run pytest
uv run ruff check
uv run ty check src/