FEATURE: Path Discovery and Projection

Purpose

Implement filters that discover paths through JSON values and construct projections from selected paths.

Behavior

• path emits path arrays for exact and filtered path expressions.
• paths emits non-empty paths to values, optionally filtered by a predicate.
• Recursive descent preserves traversal order.
• pick creates a projection containing the requested paths and preserves missing branches as null where jq specifies.
• Invalid path expressions raise runtime errors.

Programmatic Acceptance

=== AC path-001-conformance ===
Intent: The authoritative corpus slice covering path discovery and projection executes and passes.
Suite: scoped
Requires: executable=python3; scope=test

import json import os import subprocess import sys

select = r"path\(|paths|pick\(" result = subprocess.run( [sys.executable, "sources/run_conformance.py", "--select", select, "--json"], capture_output=True, text=True, env={**os.environ, "JQ": f"{os.getcwd()}/jq"}, ) print(result.stdout) print(result.stderr, file=sys.stderr) report = json.loads(result.stdout) summary = report["summary"] assert sum(summary.values()) > 0 assert summary["fail"] == 0 assert summary["error"] == 0 assert result.returncode == 0 === END AC path-001-conformance ===

User Acceptance

• None.

Guardrails

• Path arrays contain only valid string keys and numeric indices.
• Path discovery must preserve generator ordering and multiplicity.
• Projection and discovery must not mutate the source value.