=== BEGIN ARTIFACT FEATURE-FUNC-004.md ===
# FEATURE: Destructuring Patterns and Alternatives

| Field       | Value |
|-------------|-------|
| Version     | 20260822 V1 |
| Description | Provides jq destructuring patterns and alternative bindings. |
| Depends On  | FEATURE-FUNC-003.md |
| Provides    | array patterns, object patterns, missing bindings, ?// alternatives |
| Consumes    | lexical bindings, function evaluator |

## Questions

- None.

## Purpose

Support array and object destructuring in `as` bindings, bind absent members as `null`, and backtrack through `?//` alternatives when a pattern or subsequent expression fails.

## Behavior

- Array patterns bind positional elements and use `null` for missing positions.
- Object patterns bind named fields and nested patterns.
- Alternative patterns try later alternatives when an earlier binding fails.
- Variables introduced by successful alternatives remain available to the following filter.
- Errors from the final alternative propagate as runtime errors.

## Programmatic Acceptance

=== AC func-004-conformance ===
Intent: The authoritative corpus slice covering destructuring patterns and alternative bindings executes and passes.
Suite: scoped
Requires: executable=python3; scope=test

import json
import os
import subprocess
import sys

select = r"\?//| as \{"
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 func-004-conformance ===

## User Acceptance

- None.

## Guardrails

- Preserve lexical scope and generator backtracking.
- Do not silently convert a final alternative error into a successful value.
=== END ARTIFACT ===
=== BEGIN ARTIFACT FEATURE-PATH-001.md ===
# FEATURE: Path Discovery and Projection

| Field       | Value |
|-------------|-------|
| Version     | 20260822 V1 |
| Description | Provides jq path discovery and projection filters. |
| Depends On  | FEATURE-FUNC-004.md |
| Provides    | path, paths, pick |
| Consumes    | field and index access, recursive generators, destructuring |

## Questions

- None.

## 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.
=== END ARTIFACT ===
=== BEGIN ARTIFACT FEATURE-PATH-002.md ===
# FEATURE: Path Access and Mutation Primitives

| Field       | Value |
|-------------|-------|
| Version     | 20260822 V1 |
| Description | Provides jq nested path access, update, and deletion primitives. |
| Depends On  | FEATURE-PATH-001.md |
| Provides    | getpath, setpath, delpaths |
| Consumes    | path discovery, jq value model |

## Questions

- None.

## Purpose

Implement immutable access and mutation of nested arrays and objects through explicit path arrays.

## Behavior

- `getpath` reads values at supplied paths and returns `null` for absent paths where specified.
- `setpath` creates missing object and array structure and updates existing values.
- `delpaths` removes all requested paths without mutating the original input.
- Multiple path expressions preserve their generator order.
- Invalid path types, negative indices, and excessive path depth produce jq runtime errors or no-ops according to the specification.

## Programmatic Acceptance

=== AC path-002-conformance ===
Intent: The authoritative corpus slice covering getpath, setpath, and delpaths executes and passes.
Suite: scoped
Requires: executable=python3; scope=test

import json
import os
import subprocess
import sys

select = r"getpath|setpath|delpaths"
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-002-conformance ===

## User Acceptance

- None.

## Guardrails

- Values remain immutable from the filter author's perspective.
- Do not treat invalid paths as valid object keys or array indices.
- Enforce the supplied depth and indexing semantics.
=== END ARTIFACT ===
=== BEGIN ARTIFACT FEATURE-PATH-003.md ===
# FEATURE: Deletion and Assignment Operators

| Field       | Value |
|-------------|-------|
| Version     | 20260822 V1 |
| Description | Provides jq deletion and assignment operators over path expressions. |
| Depends On  | FEATURE-PATH-002.md |
| Provides    | del, =, |=, +=, -=, *=, /=, %=, //=
| Consumes    | path discovery, getpath, setpath, delpaths |

## Questions

- None.

## Purpose

Implement jq's immutable deletion, plain assignment, update assignment, and arithmetic assignment semantics.

## Behavior

- `del` removes values selected by one or more path expressions.
- Plain assignment evaluates the right-hand side against the original input and uses every produced value.
- Update assignment evaluates the right-hand side against each selected value and uses the first result.
- Arithmetic assignments apply the corresponding operator to selected values.
- Defined-or assignment replaces false or null values with the right-hand result.
- Multi-path assignments preserve jq's output ordering and multiplicity.

## Programmatic Acceptance

=== AC path-003-conformance ===
Intent: The authoritative corpus slice covering deletion and assignment operators executes and passes.
Suite: scoped
Requires: executable=python3; scope=test

import json
import os
import subprocess
import sys

select = r"=|\|=|\+="
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-003-conformance ===

## User Acceptance

- None.

## Guardrails

- Assignment must produce immutable values and must not leak mutations between outputs.
- Preserve the distinction between `=` and `|=`.
- Empty update streams delete the selected path.
=== END ARTIFACT ===
=== BEGIN ARTIFACT FEATURE-PATH-004.md ===
# FEATURE: Complex Assignment Edge Cases

| Field       | Value |
|-------------|-------|
| Version     | 20260822 V1 |
| Description | Completes jq assignment behavior for iterated, invalid, and deep paths. |
| Depends On  | FEATURE-PATH-003.md |
| Provides    | iterated assignment, empty updates, array expansion, invalid and deep paths |
| Consumes    | deletion and assignment operators |

## Questions

- None.

## Purpose

Handle complex assignment cases involving iterated paths, empty updates, array expansion, invalid indices, NaN indices, string slices, and depth limits.

## Behavior

- Assignments through iterated and filtered paths update every selected location in jq order.
- Empty updates remove selected array or object members.
- Assignments beyond an array's current length expand it with `null` values where specified.
- Negative, fractional, and NaN indices follow jq's access and mutation rules.
- String slices cannot be updated when jq forbids string mutation.
- Path, containment, comparison, serialization, and merge depth limits are enforced.

## Programmatic Acceptance

=== AC path-004-conformance ===
Intent: The authoritative corpus slice covering complex assignment edge cases executes and passes.
Suite: scoped
Requires: executable=python3; scope=test

import json
import os
import subprocess
import sys

select = r"negative|NaN|depth|empty"
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-004-conformance ===

## User Acceptance

- None.

## Guardrails

- Reject invalid mutations with runtime errors rather than corrupting values.
- Preserve partial output before runtime failure.
- Enforce documented depth limits without recursion runaway.
=== END ARTIFACT ===