feat(parser): pattern parser — NodePattern, RelPattern, PathPattern

[DecisionNerd]

Summary

• Implements crates/gf-cypher/src/parser/patterns.rs (chunk B of rust: implement recursive-descent + Pratt parser for gf-cypher #554)
• parse_node_pattern: anonymous (), variable, labels, multi-label, inline property map
• parse_rel_pattern: all 6 forms (-->, <--, --, -[r]->, <-[r]-, -[r]-), type lists, variable-length ranges, inline properties
• parse_pattern: chained path + named path binding (p = ...)
• parse_pattern_list: comma-separated pattern list
• All property values delegate to parse_expr from chunk A
• 24 unit tests; all 73 gf-cypher tests pass

Test plan

• cargo test -p gf-cypher — 73 tests pass
• cargo clippy -p gf-cypher -- -D warnings — clean
• cargo fmt --all -- --check — clean

Closes #651
Part of #554

🤖 Generated with Claude Code

Note

Add pattern parser for NodePattern, RelPattern, and PathPattern in gf-cypher

• Adds a new patterns submodule to the Cypher parser exposing parse_node_pattern, parse_pattern, and parse_pattern_list in patterns.rs.
• parse_node_pattern handles (), (n), (:Label), and (n:Label {props}) forms, producing a NodePattern with var, labels, properties, and span.
• parse_rel_pattern supports all relationship syntaxes (-->, <--, --, bracketed forms) with direction, optional variable, type list, hop ranges, and properties; invalid combinations like <-[r]-> produce structured errors.
• parse_pattern composes node and relationship elements into a PathPattern, optionally with a named path prefix (var =); parse_pattern_list handles comma-separated lists of patterns.

^{Macroscope summarized 34b9a3b.}

Summary by CodeRabbit

• New Features

  • Publicly exposed pattern parsing: full path patterns, named paths, node labels, and property maps.
  • Support for directional relationships and variable-length hops (open or ranged).
  • Parsing of comma-separated pattern lists.

• Tests

  • Added comprehensive tests for node/relationship parsing, hop ranges, chaining, named paths, and span coverage.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 413c5e9d-8320-4ff9-9deb-328845966b9c

📥 Commits

Reviewing files that changed from the base of the PR and between 8665cd5 and 34b9a3b.

📒 Files selected for processing (1)

• crates/gf-cypher/src/parser/patterns.rs

---

Walkthrough

Implements a Cypher path pattern parser: new public patterns module with parse_node_pattern, parse_pattern, parse_pattern_list; parses node patterns, relationship syntaxes (directions, types, variable-length hops), assembles chained PathPattern (optional named path), includes helpers and tests.

Changes

Pattern Parser Implementation

Layer / File(s)	Summary
Module declaration and re-exports crates/gf-cypher/src/parser/mod.rs	Parser module declares the public patterns submodule and re-exports the public entry points (parse_node_pattern, parse_pattern, parse_pattern_list) alongside existing parse_expr.
Public entry points crates/gf-cypher/src/parser/patterns.rs (lines 1–57)	Defines the public functions: parse_pattern (single pattern, optional name) and parse_pattern_list (comma-separated patterns).
Node pattern parsing crates/gf-cypher/src/parser/patterns.rs (lines 59–91)	Parses node patterns in (...): optional variable, zero or more labels, optional {...} property map (delegates to parse_expr), and span construction.
Relationship parsing and hop ranges crates/gf-cypher/src/parser/patterns.rs (lines 97–299)	Parses relationship syntaxes (-->, <--, --, -[...] ->, etc.), direction, optional relationship variable/type lists, * variable-length forms (*, *N, *N..M, *..M, *N..), optional property maps; builds RelPattern spans.
Helpers: identifiers & labels crates/gf-cypher/src/parser/patterns.rs (lines 304–395)	Utility functions to consume identifiers, accept keyword tokens as label/type names, and map tokens to label/type strings.
Test suite crates/gf-cypher/src/parser/patterns.rs (lines 400–649)	Unit tests for node parsing variants, relationship directions/types/hop ranges, chained path assembly, named-path parsing, pattern-list parsing, and span sanity checks.

Sequence Diagram(s)

sequenceDiagram
  participant TokenStream
  participant parse_pattern
  participant parse_node_pattern
  participant parse_rel_interior
  participant parse_expr
  TokenStream->>parse_pattern: provide tokens for pattern (maybe "p = (a)-[:K]->(b)")
  parse_pattern->>parse_node_pattern: parse initial node `( ... )`
  parse_node_pattern->>parse_expr: parse `{...}` property map (if present)
  parse_pattern->>parse_rel_interior: parse relationship `-[]->` or `--`
  parse_rel_interior->>parse_expr: parse rel property map (if present)
  parse_pattern->>parse_node_pattern: parse next node
  parse_pattern->>TokenStream: return PathPattern AST (with name/span)

Loading

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~45 minutes

Possibly related PRs

• DecisionNerd/graphforge#654: Earlier recursive-descent parser scaffold and initial parser/mod.rs wiring related to this patterns addition.
• DecisionNerd/graphforge#655: Adjusted parser re-exports around parse_expr; touches the same module-level wiring updated here.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change: implementing a pattern parser with NodePattern, RelPattern, and PathPattern support.
Linked Issues check	✅ Passed	The PR successfully implements all requirements from #651: parse_node_pattern, parse_pattern, parse_pattern_list public APIs; node/rel pattern parsing with all forms; named paths; 24 unit tests; all 73 tests passing.
Out of Scope Changes check	✅ Passed	All changes are scoped to the pattern parser implementation. The PR adds patterns.rs with pattern parsing logic and updates mod.rs to re-export public functions, both directly aligned with #651 and #554 objectives.
Docstring Coverage	✅ Passed	Docstring coverage is 92.31% which is sufficient. The required threshold is 80.00%.
Description check	✅ Passed	The pull request description is detailed and comprehensive, covering all major sections of the template including summary, type of change, related issues, and test plan.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feature/651-pattern-parser

---

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.09%. Comparing base (1a4f1cc) to head (34b9a3b).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #656   +/-   ##
=======================================
  Coverage   84.09%   84.09%           
=======================================
  Files          49       49           
  Lines       12921    12921           
  Branches     3628     3628           
=======================================
  Hits        10866    10866           
  Misses       1270     1270           
  Partials      785      785           

Flag	Coverage Δ
full-coverage	84.09% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
parser	92.93% <ø> (ø)
planner	79.90% <ø> (ø)
executor	75.46% <ø> (ø)
storage	98.68% <ø> (ø)
ast	97.51% <ø> (ø)
types	90.66% <ø> (ø)

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 1a4f1cc...34b9a3b. Read the comment docs.

🚀 New features to boost your workflow:

• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[coderabbitai]

Actionable comments posted: 3

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@crates/gf-cypher/src/parser/patterns.rs`:
- Around line 109-124: The span for RelPattern currently ends at r_brace which
excludes the trailing direction token; update the span to include the consumed
direction token by advancing the end position to the token you matched when
setting direction (i.e., when ts.eat_if(&Tok::RightArrow) or
ts.eat_if(&Tok::Minus)); locate the block that builds RelPattern (uses vars var,
types, direction, min_hops, max_hops, properties, span: Span::new(start,
r_brace)) and replace the span end with the end position of the consumed
direction token (use the token's span/end returned by the eat/eat_if call or
capture the token node/end and pass that instead of r_brace) so spans for -[r]->
and -[r]- include the final arrow/dash.
- Around line 134-140: After parsing the `]` the code currently treats a
consumed Tok::RightArrow as Direction::Undirected (commenting "<-[r]-> means
both directions"); instead reject the two-headed arrow instead of mapping it to
Direction::Undirected. Replace the branch that returns Direction::Undirected on
ts.eat_if(&Tok::RightArrow) with a return Err(...) from the parser (using ts.err
with a clear message like "`<-[...]->` is not allowed"), keep the Tok::Minus
branch returning Direction::In, and leave the existing fallback error unchanged
so only the allowed `-[...]-`, `-...->`, and `->...-` forms are accepted.
- Around line 244-273: parse_hop_range currently returns (None, None) for a bare
`*`, which collides with the same tuple used for non-variable relationships;
change the default arm so a bare `*` is represented distinctly (e.g., return
(Some(0), None) to mean variable-length any hops) and adjust the function
docstring accordingly so callers can distinguish variable-length (`*`) from
non-variable edges; update parse_hop_range (and any related comments) to use
this new representation.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 2df7a196-a4de-4983-aa3b-e11e9ce50560

📥 Commits

Reviewing files that changed from the base of the PR and between 1a4f1cc and 165682a.

📒 Files selected for processing (2)

• crates/gf-cypher/src/parser/mod.rs
• crates/gf-cypher/src/parser/patterns.rs