lfe_edlin_expand.erl - Command Line Expansion

Purpose: Provide tab completion and expansion for the LFE shell.

Location: src/lfe_edlin_expand.erl Size: 232 LOC, 7.8KB

Module Classification: Shell support, command completion

Public API

expand(Before) -> {yes, Expansion, Matches} | no

Expand command-line input. Located at lfe_edlin_expand.erl:42-45.

Parameters:

• Before - String before cursor
• Returns:
  • {yes, Expansion, Matches} - Possible expansions
  • no - No completions available

Completion Types

Module Name Completion:

lfe> (lists:m<TAB>
→ lists:map  lists:max  lists:member  ...

Function Name Completion:

lfe> (list<TAB>
→ lists  list-comprehension  ...

Variable Name Completion:

lfe> my-var<TAB>
→ my-variable-name

Local Bindings: Completes from current environment.

Implementation

Tokenization (expand/1 at lines 47-89):

1. Parse Before string into tokens
2. Identify last token (completion target)
3. Determine context (module, function, variable)
4. Find matches
5. Return common prefix + alternatives

Module/Function Matching (match_module_functions/2 at lines 134-178):

match_module_functions(Prefix, Env) ->
    % Get all loaded modules
    Modules = code:all_loaded(),
    % Get module exports
    Exports = [Mod:module_info(exports) || {Mod, _} <- Modules],
    % Filter by prefix
    filter_matches(Prefix, flatten(Exports)).

Local Binding Matching (match_local_bindings/2 at lines 182-214):

Searches current environment for matching variable names.

Dependencies

LFE modules:

• lfe_env - Access to bindings
• lfe_scan - Tokenization

Erlang stdlib:

• code, lists, string

Used By

• lfe_shell - Via io:setopts([{expand_fun, Fun}])

Special Considerations

Performance: Completion must be fast (< 100ms) for responsive UX.

Context Sensitivity: Understands LFE syntax to provide relevant completions.

Module Loading: Only completes for loaded modules (doesn't search filesystem).