piccolo-sql-guard

A community-maintained static checker for unsafe Piccolo raw SQL construction.

What it checks

PQS004 — unsafe SQL token builders

PQS004 performs cross-function analysis to find SQL builder functions that interpolate parameters of unsafe type and are reachable from a Piccolo raw SQL sink. A parameter is safe when its type annotation constrains it to a finite set of values:

• Literal["ASC", "DESC"] — explicitly enumerated strings
• bool — Boolean (maps to e.g. " WHERE active" / "")
• int / float — numeric constants
• A local Enum / StrEnum subclass

A plain str parameter is unsafe and triggers PQS004.

# PQS004 fires — sort_col is unconstrained str
def build(sort_col: str) -> str:
    return f"SELECT * FROM my_model ORDER BY {sort_col}"

# Safe — Literal constrains the set of allowed values
def build(direction: Literal["ASC", "DESC"]) -> str:
    return f"SELECT * FROM my_model ORDER BY id {direction}"

PQS004 also follows simple helper-call chains and common string-building patterns such as f-strings, string concatenation, and str.join() over literal containers.

Quick start

pip install piccolo-sql-guard
piccolo-sql-guard src/

Usage

piccolo-sql-guard [PATH ...]                  # scan paths
piccolo-sql-guard --format json src/          # JSON output
piccolo-sql-guard --select PQS001,PQS002 src/ # enable specific rules
piccolo-sql-guard --ignore PQS004 src/        # disable specific rules
piccolo-sql-guard --statistics src/           # print file/violation counts
piccolo-sql-guard --profile src/              # print per-phase timing
piccolo-sql-guard --version

Unknown rule codes passed to --select or --ignore are treated as configuration errors so CI does not accidentally run with an empty ruleset.

Development

This project uses uv for the local development environment and lockfile. The package supports Python 3.11 through 3.14.

uv sync --extra dev
uv run --extra dev pytest
uv run --extra dev ruff check .
uv run --extra dev mypy src

Configuration

piccolo-sql-guard.toml or pyproject.toml:

[tool.piccolo-sql-guard]
include = ["src"]
exclude = ["migrations", ".venv"]
select = ["PQS001", "PQS002", "PQS003", "PQS004"]
ignore = []
builder_allowlist = ["build_*_sql"]
piccolo_modules = ["piccolo"]
output_format = "text"
pqs004_max_iterations = 5   # fixed-point iteration cap for recursive builders

builder_allowlist

A list of glob patterns matching builder function names that are assumed safe and excluded from PQS004 analysis. Use this for third-party or generated builders you cannot annotate.

pqs004_max_iterations

Maximum number of fixed-point iterations for recursive or mutually-recursive builder groups (default: 5). Increase if you have deeply recursive builders; decrease if scan time is a concern.

Limitations

piccolo-sql-guard is a best-effort static checker. Dynamic dispatch, complex container mutation, runtime imports, and values assembled outside the scanned source tree may be treated as unknown or missed. Treat a clean run as a lint signal, not as proof that every raw SQL path is injection-safe.

Exit codes