RFC 3987 Syntax Validation

1.1.0 · active · verified Sat Mar 28

rfc3987-syntax is a Python library (current version 1.1.0) that provides helper functions to syntactically validate strings according to the ABNF grammar defined in RFC 3987, which specifies Internationalized Resource Identifiers (IRIs). It is lightweight, permissively licensed (MIT), and leverages the Lark parsing library. The project strictly focuses on ABNF syntax validation, explicitly stating that additional semantic rules (like Unicode normalization or BiDi constraints) must be handled separately. With a relatively active release cadence, its latest major update (v1.1.0) introduced support for IRI-reference and absolute-IRI.

Warnings

gotcha This library *only* performs syntactic validation of RFC 3987 based on ABNF grammar. It does not validate semantic rules such as Unicode Normalization Form C (NFC), Bidirectional text (BiDi) constraints, port number ranges (0-65535), valid IPv6 compression, or context-aware percent-encoding requirements. These must be enforced separately for full compliance.
Fix: Implement additional logic for semantic validation as required by your application.
gotcha This `rfc3987-syntax` package is a distinct project and is *not* affiliated with the older, GPL-licensed `rfc3987` Python package by Daniel Gerber, which has a different scope. Ensure you are installing `rfc3987-syntax` to avoid licensing conflicts or unexpected API differences.
Fix: Confirm the correct package name during installation: `pip install rfc3987-syntax`.
breaking Version 1.1.0 introduced explicit support for `IRI-reference` and `absolute-IRI` terms and fixed a bug related to single quote sub-delimiters. While primarily adding functionality, these changes *could* subtly alter validation results for certain inputs that were previously considered invalid or parsed differently in older versions.
Fix: Review validation logic and expected outcomes when upgrading from versions prior to 1.1.0, especially for inputs involving IRI-references, absolute-IRIs, or single quotes within delimited components.

Install

pip install rfc3987-syntax Install latest version

Imports

is_valid_syntax

from rfc3987_syntax import is_valid_syntax

RFC3987_SYNTAX_TERMS

from rfc3987_syntax import RFC3987_SYNTAX_TERMS

Quickstart

Demonstrates how to list supported validation terms and use the `is_valid_syntax` function to check if a string conforms to a specific RFC 3987 syntax rule, such as 'iri'.

from rfc3987_syntax import is_valid_syntax, RFC3987_SYNTAX_TERMS

# List all supported validation terms
print(f"Supported terms: {RFC3987_SYNTAX_TERMS}\n")

# Validate a string against a specific term
if is_valid_syntax(term='iri', value='http://example.com/path/to/resource?query=param#fragment'):
    print("✓ 'http://example.com/path/to/resource?query=param#fragment' is a valid IRI syntax")
else:
    print("✗ Invalid IRI syntax")

# Example of invalid syntax
if not is_valid_syntax(term='iri', value='not-an-iri-with- space'):
    print("✗ 'not-an-iri-with- space' is invalid IRI syntax as expected")

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