feat: Lark parser POC for IOS ACL grammar (closes #374)#375
feat: Lark parser POC for IOS ACL grammar (closes #374)#375
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| # --- Logging --- | ||
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| def ios_log(self, items): | ||
| return "log" |
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ios_log discards log-input token value silently
Medium Severity
The ios_log method hardcodes returning "log" regardless of whether the matched token was "log" or "log-input". The grammar's IOS_LOG terminal matches both, but the transformer discards the distinction. This silently downgrades log-input (which records the input interface) to plain log, causing data loss on round-trip parsing. The actual token value from items[0] is not consulted.
- Fix icomment handler to push Comment to global Comments list during transformation (not deferred to start), matching SimpleParse behavior - Add TODO noting log/log-input distinction is a pre-existing limitation in handle_ios_match, not introduced by the Lark port
Term.__init__() rebinds the module-level Comments list in support.py. Importing Comments by name creates a local binding that goes stale after Term drains it. Access via acl_support.Comments instead.
- _ios_line and icomment rules used _WS (space/tab/newline) where the original SimpleParse grammar uses ts (space/tab only). This caused ambiguity with the NEWLINE token in the start rule. - Removed unused imports: Tree, v_args, Discard, ports, icmp_types, icmp_codes, tcp_flag_specials, make_inverse_mask, strip_comments, exceptions.
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Cursor Bugbot has reviewed your changes and found 1 potential issue.
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Empty 'remark' lines (remark followed by newline with no body text) would fail to parse. The original grammar uses zero-or-more for remark_body. Match icomment's pattern of making the body optional.
Summary
Proof-of-concept evaluating Lark as a replacement for SimpleParse, which is broken on Python 3.12+ (C extension build failures).
Closes #374
Performance Comparison
All tests on Apple Silicon, Python 3.11, Lark 1.3.1 (Earley parser).
Key Findings
_TSvs_WS), which is a fundamental LALR(1) limitationEstimated Effort for Full Port
Files
ios_acl.lark— Complete Lark grammar (148 lines)ios_transformer.py— Lark Transformer producing Trigger ACL objects (200 lines)test_parse.py— 18 test cases covering all IOS ACL featuresbenchmark.py— Performance comparison scriptRESULTS.md— Detailed findings and analysisThis is a proof-of-concept — not production-ready. Files are in
poc-lark/intentionally. The purpose is to validate the approach before investing in a full port.Note
Low Risk
Changes are additive and isolated to
poc-lark/with no integration into production parsing paths; main risk is future adoption of the new grammar/transformer without broader test coverage.Overview
Adds a self-contained
poc-lark/proof-of-concept that ports Trigger’s IOS ACL SimpleParse grammar to a Lark (Earley) grammar and transformer, producing the sameACL/Termobjects via existinghandle_ios_match/handle_ios_acllogic.Includes a small test runner (
test_parse.py) covering 18 IOS ACL cases, a benchmark script comparing SimpleParse vs Lark performance (and demonstrating LALR incompatibility), and a writeup (RESULTS.md) documenting correctness/perf findings and the recommendation to use Earley.Written by Cursor Bugbot for commit 500cc63. This will update automatically on new commits. Configure here.