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Requested by Peter · project thread

The Rust crate gets read access to the LALR automaton and the parser state, as Python Lark leaves them public, so that a tool can print the automaton and recover from errors itself. etalii.adp spec 035 needs this (amendment of 2026-10-24, research R9, tasks T164 and T165), to rebuild adp-atd-grammar and adp-atd-syntax on etalii-lark. It's meant for release as 0.4.0. This PR is Rust only; the .NET and TypeScript ports are unchanged.

What

• Lark::parse_table() -> Option<&ParseTable> gives a LALR parser's table, as Python Lark's parser.parser.parser.parse_table; it is None for Earley and CYK. parsers::lalr_analysis is public, with ParseTable and LalrAction (its Action) re-exported at the root.
• ParserState (now re-exported at the root) gets three methods:
  • state_stack() and value_stack(), as Python's state_stack and value_stack;
  • truncate(depth), which pops both stacks to depth states and keeps at least the start state. It returns the popped values, as Lark's on_error handlers pop them.
• InteractiveParser gets two methods:
  • parser_state_mut(), to change the state for recovery;
  • next_token(), which lexes one token for the current parser state without feeding it. With the contextual lexer it matches only what the state accepts.

Tests

rust/etalii-lark/tests/lalr_access.rs covers:

• the table is the parser's: shifts go to its states, reductions name its rules, and Earley has none;
• next_token lexes per state: if if reads the keyword, then a name;
• recovery: read the stacks, pop back to the state that read {, skip what that state does not read, and resume the parse.

On this branch, cargo fmt --check, cargo clippy --all-targets -- -D warnings and cargo test pass, the conformance suite included.

I also used the branch to prototype etalii.adp's table printing. Its normalized table for the ATD grammar equals what Python Lark gives (atd.tables.json) byte for byte.

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