Crate lattice_snippet 

TextMate-format snippet engine for lattice (Phase 4.2.g.4; design in docs/dev/architecture/insert-completion.md §8).

Three responsibilities:

1. Parse TextMate / LSP snippet body syntax (placeholders, choices, variables, escapes) into a stream of SnippetTokens.
2. Render that stream into the literal text the editor inserts plus the per-tabstop byte ranges (RenderedSnippet) – so the host can wire placeholder navigation without re-parsing.
3. Track the in-flight snippet expansion’s tabstop state via ActiveSnippet so <Tab> / <S-Tab> step through placeholders and edits in one tabstop ripple to its mirrors.

Drop-in compatibility with the VS Code TextMate JSON format is the design target: friendly-snippets (the community-maintained corpus most editors pull from) loads verbatim. See load for the JSON ingestion path and registry::SnippetRegistry for per-language storage.

Variables are resolved against an editor-supplied VariableContext – the host fills in TM_FILENAME / CLIPBOARD / etc. when the snippet expands. v1 supports the TextMate / VS Code built-in variable set; transformation placeholders (${1/pattern/replacement/}) parse to a transformation token but apply as their original text in v1; full regex transformation lands as polish.

This crate has no editor dependency. Tests parse + render + drive the active-snippet state machine without touching any rope or buffer; the host wires ActiveSnippet to its buffer-mutation pipeline.

Re-exports

pub use crate::activation::SnippetActivation;

pub use crate::activation::SnippetActivationMode;

pub use crate::activation::SnippetActivationPolicyHandle;

pub use crate::activation::SnippetLanguages;

pub use crate::activation::fold_activation_policy;

pub use crate::active::ActiveSnippet;

pub use crate::active::TabstopGroup;

pub use crate::builtins::builtin_packs;

pub use crate::builtins::load_builtins;

pub use crate::builtins::load_builtins_into;

pub use crate::load::LoadError;

pub use crate::load::load_pack;

pub use crate::load::load_pack_from_str;

pub use crate::modes::SNIPPET_COMPLETION_SOURCE_ID;

pub use crate::modes::SNIPPET_PAYLOAD_KIND_ID;

pub use crate::modes::SnippetCompletionMode;

pub use crate::modes::SnippetCompletionSource;

pub use crate::modes::SnippetMode;

pub use crate::modes::register_snippet_modes;

pub use crate::parse::ParseError;

pub use crate::parse::parse;

pub use crate::registry::Snippet;

pub use crate::registry::SnippetMeta;

pub use crate::registry::SnippetRegistry;

pub use crate::render::RenderedSnippet;

pub use crate::render::TabstopRange;

pub use crate::session::SnippetSession;

pub use crate::session::SnippetSessionHandle;

pub use crate::session::snippet_active_predicate;

pub use crate::token::ChoiceOption;

pub use crate::token::SnippetBody;

pub use crate::token::SnippetToken;

pub use crate::variables::VariableContext;

pub use crate::variables::builtin_variables;

Modules

activation

SN.3b — config-driven snippet activation policy.

active

Active-snippet state machine. The host instantiates one ActiveSnippet when a snippet expands; while it’s the “active” snippet, <Tab> / <S-Tab> step through placeholders and edits to one tabstop ripple to the others that share its index.

builtins

Built-in snippet packs embedded in the binary.

load

TextMate JSON loader – the format VS Code uses and friendly-snippets ships in. Reading a friendly-snippets pack is a matter of pointing at its JSON files; no conversion or shim code.

modes

snippet-completion-mode (insert-completion.md §12, CSM.5).

parse

TextMate / LSP snippet body parser. Produces a SnippetBody from a string; consumers (renderer + active-snippet state machine) walk the resulting tokens.

picker_sources

:picker snippets source generator.

registry

Per-language snippet registry. Stores parsed bodies keyed by trigger prefix; the host’s gen:snippet source consults this registry per-popup-trigger.

render

Render a parsed SnippetBody to literal text plus per-tabstop byte ranges. Output feeds the editor’s edit pipeline (insert the text, then track the ranges as the user types into placeholders).

session

SN.2: the live snippet-expansion session, relocated off the host Editor so the mode-owned placeholder-navigation handlers can reach it.

token

Parsed snippet body: the token stream a crate::parse::parse produces and crate::render::render walks.

variables

Variable resolution for snippet expansion. The host fills in a VariableContext with file / cursor / clipboard info; the renderer asks the context for each $VAR it encounters.