Custom rules

Metacrafter loads rules from every directory in the effective rulepath:

1. Built-in rules/ shipped with the package (when auto_rules is true)
2. Extended metacrafter-rules pack if metacrafter[rules] is installed
3. Extra rulepath entries and --rulepath flags

Duplicate keys are skipped with a warning. Set auto_rules: false for a custom-only set.

Match engines

match	Behavior
text	Exact match against comma-separated tokens
ppr	PyParsing expression in a restricted namespace
func	Importable Python function (value) -> bool

Rules apply to fields (column names) or data (values).

Function

runpabyfunc:
  key: runpa
  name: Russian legal act / law
  maxlen: 500
  minlen: 3
  priority: 1
  match: func
  type: data
  rule: metacrafter.rules.ru.gov.is_ru_law

Any importable path works (mypackage.validators.is_widget_id) as long as the module is on PYTHONPATH.

Exact text

midname:
  key: person_midname
  name: Person midname by known field name
  rule: midname,secondname,middlename,mid_name,middle_name
  type: field
  match: text

PyParsing

rukadastr:
  key: rukadastr
  name: Russian land territory cadastral identifier
  rule: Word(nums, min=1, max=2) + Literal(':').suppress() + Word(nums, min=1, max=2) + Literal(':').suppress() + Word(nums, min=6, max=7) + Literal(':').suppress() + Word(nums, min=1, max=6)
  maxlen: 20
  minlen: 12
  priority: 1
  match: ppr
  type: data

ppr rules run with PyParsing primitives only (Word, Literal, nums, alphas, …). import / eval / exec are not available.

Typical metadata

key, name, type, match, rule, priority, minlen / maxlen, contexts, langs, country, is_pii, optional validator.

Align key with a registry datatype id.

Inspect

metacrafter rules list --rulepath ./custom_rules

See rules and Architecture.