fix: recognize Lua function nodes in complexity metrics computation (docs check acknowledged)

codegraph complexity --file <f> --health -T --json returned functions:[]
for every Lua file even though symbol extraction (codegraph where) already
worked correctly. Root cause: Lua had zero entries in COMPLEXITY_RULES /
HALSTEAD_RULES (src/ast-analysis/rules/index.ts) and the native mirror
(lang_rules / halstead_rules in crates/codegraph-core/src/ast_analysis/
complexity.rs) — not a wrong node-type mapping, but a completely missing
per-language configuration on both engines, so the complexity visitor never
ran for Lua at all.

Adds complexityLua/halsteadLua (src/ast-analysis/rules/b3.ts, wired into
COMPLEXITY_RULES/HALSTEAD_RULES in rules/index.ts) and the matching
LUA_RULES/LUA_HALSTEAD (crates/codegraph-core/src/ast_analysis/
complexity.rs, wired into lang_rules/halstead_rules), derived from the real
tree-sitter-lua grammar shape (verified by parsing probe snippets with both
the WASM grammar and the native tree-sitter-lua crate): elseif_statement/
else_statement are flat siblings of if_statement via repeated `alternative:`
fields (same shape as Python's elif_clause/else_clause), and Lua's single
generic binary_expression node covers arithmetic/comparison/logical
operators alike, filtered by operator token. function_declaration matches
the same node type the existing extractor and dataflowLua rules already use,
so complexity results attach to the same definitions `where` reports. Also
adds a Lua entry to the LOC comment-prefix maps (`--`) on both engines,
which were defaulting to C-style prefixes and undercounting comment lines.

Verified against all 5 Lua files in the repo (tracer + 4 fixtures) via both
engines. Filed #1922 (WASM-only parity gap for files where every function
has a dot-qualified name, e.g. Lua's `M.foo` module pattern) and #1923
(the same missing-complexity-config gap affects 24 other languages) as
separate follow-ups rather than expanding this fix.

Fixes #1782

Author: carlos-alm

crates/codegraph-core/src/ast_analysis/complexity.rs

@@ -427,6 +427,44 @@ pub static BASH_RULES: LangRules = LangRules {
     switch_like_nodes: &["case_statement"],
 };
 
+// Lua's `if_statement` is flat, not nested: `elseif`/`else` are separate node
+// kinds (`elseif_statement`, `else_statement`) attached to the *same*
+// `if_statement` via repeated `alternative:` fields — confirmed by parsing
+// `if a then .. elseif b then .. else .. end` with tree-sitter-lua and
+// inspecting the S-expression. Structurally identical to Python's
+// elif_clause/else_clause (Pattern B), not JS's nested else_clause>if_statement
+// (Pattern A) or Go's alternative-holds-nested-if (Pattern C) — so
+// else_via_alternative: false, and neither elseif_statement nor else_statement
+// is in nesting_nodes (they're siblings of the primary if, not separately
+// nested branches). Mirrors `complexityLua` in `src/ast-analysis/rules/b3.ts`.
+//
+// binary_expression is Lua's single generic binary-op node (arithmetic,
+// comparison, concat, AND logical `and`/`or`) — same shared-type pattern as
+// Ruby's `binary` node; handle_logical_op only fires when `node.child(1)` (the
+// operator token) is in logical_operators, so comparisons/arithmetic sharing
+// the same node kind are correctly ignored.
+pub static LUA_RULES: LangRules = LangRules {
+    branch_nodes: &[
+        "if_statement",
+        "elseif_statement",
+        "else_statement",
+        "for_statement",
+        "while_statement",
+        "repeat_statement",
+    ],
+    case_nodes: &[],
+    logical_operators: &["and", "or"],
+    logical_node_types: &["binary_expression"],
+    optional_chain_type: None,
+    nesting_nodes: &["if_statement", "for_statement", "while_statement", "repeat_statement"],
+    function_nodes: &["function_declaration"],
+    if_node_type: Some("if_statement"),
+    else_node_type: Some("else_statement"),
+    elif_node_type: Some("elseif_statement"),
+    else_via_alternative: false,
+    switch_like_nodes: &[],
+};
+
 /// Look up complexity rules by language ID (matches `COMPLEXITY_RULES` keys in JS).
 pub fn lang_rules(lang_id: &str) -> Option<&'static LangRules> {
     match lang_id {
@@ -444,6 +482,7 @@ pub fn lang_rules(lang_id: &str) -> Option<&'static LangRules> {
         "swift" => Some(&SWIFT_RULES),
         "scala" => Some(&SCALA_RULES),
         "bash" => Some(&BASH_RULES),
+        "lua" => Some(&LUA_RULES),
         _ => None,
     }
 }
@@ -1022,6 +1061,34 @@ pub static BASH_HALSTEAD: HalsteadRules = HalsteadRules {
     skip_types: &[],
 };
 
+// Member/method access (`dot_index_expression` `.`, `method_index_expression`
+// `:`) and invocation (`function_call`) are wrapper nodes without a dedicated
+// "call happened" token, so they're counted as compound operators — mirrors
+// Python's ["call", "subscript", "attribute"]. The '.'/':' separator tokens
+// are ALSO in operator_leaf_types (matching Python counting both "attribute"
+// and "."), so member access contributes two distinct operator kinds,
+// consistent with the other languages above. Mirrors `halsteadLua` in
+// `src/ast-analysis/rules/b3.ts`.
+pub static LUA_HALSTEAD: HalsteadRules = HalsteadRules {
+    operator_leaf_types: &[
+        "+", "-", "*", "/", "//", "%", "^", "#", "..",
+        "==", "~=", "<=", ">=", "<", ">", "=",
+        "and", "or", "not",
+        "&", "|", "~", "<<", ">>",
+        ".", ",", ":", "::", ";",
+        "if", "then", "else", "elseif", "end",
+        "for", "while", "do", "repeat", "until",
+        "function", "local", "return", "break", "goto", "in",
+    ],
+    operand_leaf_types: &[
+        "identifier", "number", "string_content", "true", "false", "nil", "...",
+    ],
+    compound_operators: &[
+        "function_call", "bracket_index_expression", "dot_index_expression", "method_index_expression",
+    ],
+    skip_types: &[],
+};
+
 /// Look up Halstead rules by language ID.
 pub fn halstead_rules(lang_id: &str) -> Option<&'static HalsteadRules> {
     match lang_id {
@@ -1039,6 +1106,7 @@ pub fn halstead_rules(lang_id: &str) -> Option<&'static HalsteadRules> {
         "swift" => Some(&SWIFT_HALSTEAD),
         "scala" => Some(&SCALA_HALSTEAD),
         "bash" => Some(&BASH_HALSTEAD),
+        "lua" => Some(&LUA_HALSTEAD),
         _ => None,
     }
 }
@@ -1056,6 +1124,7 @@ pub fn comment_prefixes(lang_id: &str) -> &'static [&'static str] {
         "swift" => &["//", "/*"],
         "scala" => &["//", "/*"],
         "bash" => &["#"],
+        "lua" => &["--"],
         _ => &["//", "/*", "*", "*/"],
     }
 }
@@ -1604,4 +1673,88 @@ mod tests {
         assert_eq!(m.cognitive, 1);
         assert_eq!(m.cyclomatic, 2);
     }
+
+    // ─── Lua tests (issue #1782) ────────────────────────────────────────────
+
+    fn compute_lua(code: &str) -> ComplexityMetrics {
+        let mut parser = Parser::new();
+        parser
+            .set_language(&tree_sitter_lua::LANGUAGE.into())
+            .unwrap();
+        let tree = parser.parse(code.as_bytes(), None).unwrap();
+        let root = tree.root_node();
+        let func = find_first_function(&root, &LUA_RULES).expect("no function found");
+        compute_function_complexity(&func, &LUA_RULES)
+    }
+
+    #[test]
+    fn lua_empty_function() {
+        let m = compute_lua("local function f() end");
+        assert_eq!(m.cognitive, 0);
+        assert_eq!(m.cyclomatic, 1);
+        assert_eq!(m.max_nesting, 0);
+    }
+
+    #[test]
+    fn lua_single_if() {
+        let m = compute_lua("local function f(x)\n  if x > 0 then\n    return 1\n  end\nend");
+        assert_eq!(m.cognitive, 1);
+        assert_eq!(m.cyclomatic, 2);
+        assert_eq!(m.max_nesting, 1);
+    }
+
+    #[test]
+    fn lua_if_elseif_else() {
+        // elseif_statement/else_statement are siblings of if_statement via
+        // repeated `alternative:` fields (Pattern B, like Python's elif/else).
+        let m = compute_lua(
+            "local function f(x)\n  if x > 0 then\n    return 1\n  elseif x < 0 then\n    return -1\n  else\n    return 0\n  end\nend",
+        );
+        // if: +1 cog, +1 cyc; elseif: +1 cog, +1 cyc; else: +1 cog
+        assert_eq!(m.cognitive, 3);
+        assert_eq!(m.cyclomatic, 3);
+        assert_eq!(m.max_nesting, 1);
+    }
+
+    #[test]
+    fn lua_numeric_for_loop() {
+        let m = compute_lua("local function f()\n  for i = 1, 10 do\n    print(i)\n  end\nend");
+        assert_eq!(m.cognitive, 1);
+        assert_eq!(m.cyclomatic, 2);
+        assert_eq!(m.max_nesting, 1);
+    }
+
+    #[test]
+    fn lua_while_loop() {
+        let m = compute_lua("local function f(n)\n  while n > 0 do\n    n = n - 1\n  end\nend");
+        assert_eq!(m.cognitive, 1);
+        assert_eq!(m.cyclomatic, 2);
+        assert_eq!(m.max_nesting, 1);
+    }
+
+    #[test]
+    fn lua_repeat_until_loop() {
+        let m = compute_lua("local function f(n)\n  repeat\n    n = n - 1\n  until n <= 0\nend");
+        assert_eq!(m.cognitive, 1);
+        assert_eq!(m.cyclomatic, 2);
+        assert_eq!(m.max_nesting, 1);
+    }
+
+    #[test]
+    fn lua_logical_operators() {
+        let m = compute_lua("local function f(a, b)\n  if a and b then\n    return 1\n  end\nend");
+        // if: +1 cog, +1 cyc; and: +1 cog, +1 cyc
+        assert_eq!(m.cognitive, 2);
+        assert_eq!(m.cyclomatic, 3);
+    }
+
+    #[test]
+    fn lua_nested_if() {
+        let m = compute_lua(
+            "local function f(x, y)\n  if x > 0 then\n    if y > 0 then\n      return 1\n    end\n  end\nend",
+        );
+        assert_eq!(m.cognitive, 3);
+        assert_eq!(m.cyclomatic, 3);
+        assert_eq!(m.max_nesting, 2);
+    }
 }

src/ast-analysis/metrics.ts

@@ -71,6 +71,7 @@ const COMMENT_PREFIXES = new Map<string, string[]>([
   ['python', ['#']],
   ['ruby', ['#']],
   ['php', ['//', '#', '/*', '*', '*/']],
+  ['lua', ['--']],
 ]);
 
 /**

src/ast-analysis/rules/b3.ts

@@ -1,4 +1,4 @@
-import type { DataflowRulesConfig } from '../../types.js';
+import type { ComplexityRules, DataflowRulesConfig, HalsteadRules } from '../../types.js';
 import { makeDataflowRules } from '../shared.js';
 
 // ─── Lua ──────────────────────────────────────────────────────────────────────
@@ -30,6 +30,118 @@ export const dataflowLua: DataflowRulesConfig = makeDataflowRules({
   memberPropertyField: 'field',
 });
 
+// Lua's `if_statement` is flat, not nested: `elseif`/`else` are separate node
+// types (`elseif_statement`, `else_statement`) attached to the *same*
+// `if_statement` via repeated `alternative:` fields — confirmed by parsing
+// `if a then .. elseif b then .. else .. end` and inspecting the S-expression:
+// `(if_statement condition: (...) consequence: (...) alternative: (elseif_statement ...) alternative: (else_statement ...))`.
+// This is structurally identical to Python's elif_clause/else_clause pattern
+// (Pattern B), not JS's nested else_clause>if_statement (Pattern A) or Go's
+// alternative-field-holds-nested-if (Pattern C) — so elseViaAlternative: false
+// and neither elseif_statement nor else_statement is in nestingNodes (matching
+// how Python's elif_clause/else_clause are siblings of the primary if, not
+// separately-nested branches).
+//
+// binary_expression is Lua's single generic binary-op node (arithmetic,
+// comparison, concat, AND logical `and`/`or`) — same shared-type pattern as
+// Ruby's `binary` node. classifyLogicalOp/handleLogicalOperator only acts when
+// `node.child(1)` (the operator token) is in logicalOperators, so comparisons
+// and arithmetic on the same node type are correctly ignored.
+export const complexityLua: ComplexityRules = {
+  branchNodes: new Set([
+    'if_statement',
+    'elseif_statement',
+    'else_statement',
+    'for_statement',
+    'while_statement',
+    'repeat_statement',
+  ]),
+  caseNodes: new Set([]),
+  logicalOperators: new Set(['and', 'or']),
+  logicalNodeType: 'binary_expression',
+  optionalChainType: null,
+  nestingNodes: new Set(['if_statement', 'for_statement', 'while_statement', 'repeat_statement']),
+  functionNodes: new Set(['function_declaration']),
+  ifNodeType: 'if_statement',
+  elseNodeType: 'else_statement',
+  elifNodeType: 'elseif_statement',
+  elseViaAlternative: false,
+  switchLikeNodes: new Set([]),
+};
+
+// Member/method access (`dot_index_expression` `.`, `method_index_expression`
+// `:`) and invocation (`function_call`) are wrapper nodes without a dedicated
+// "call happened" token, so they're counted as compound operators — mirrors
+// Python's ['call', 'subscript', 'attribute']. The '.'/':' separator tokens are
+// ALSO in operatorLeafTypes (matching Python counting both 'attribute' and
+// '.'), so member access contributes two distinct operator kinds, consistent
+// with the existing per-language precedent.
+export const halsteadLua: HalsteadRules = {
+  operatorLeafTypes: new Set([
+    '+',
+    '-',
+    '*',
+    '/',
+    '//',
+    '%',
+    '^',
+    '#',
+    '..',
+    '==',
+    '~=',
+    '<=',
+    '>=',
+    '<',
+    '>',
+    '=',
+    'and',
+    'or',
+    'not',
+    '&',
+    '|',
+    '~',
+    '<<',
+    '>>',
+    '.',
+    ',',
+    ':',
+    '::',
+    ';',
+    'if',
+    'then',
+    'else',
+    'elseif',
+    'end',
+    'for',
+    'while',
+    'do',
+    'repeat',
+    'until',
+    'function',
+    'local',
+    'return',
+    'break',
+    'goto',
+    'in',
+  ]),
+  operandLeafTypes: new Set([
+    'identifier',
+    'number',
+    'string_content',
+    'true',
+    'false',
+    'nil',
+    '...',
+  ]),
+  compoundOperators: new Set([
+    'function_call',
+    'bracket_index_expression',
+    'dot_index_expression',
+    'method_index_expression',
+  ]),
+  skipTypes: new Set([]),
+};
+
 // ─── R ────────────────────────────────────────────────────────────────────────
 //
 // R functions are defined as: `name <- function_definition` (binary_operator with `<-`).

src/ast-analysis/rules/index.ts

@@ -31,6 +31,7 @@ export const COMPLEXITY_RULES: Map<string, ComplexityRules> = new Map([
   ['csharp', csharp.complexity],
   ['ruby', ruby.complexity],
   ['php', php.complexity],
+  ['lua', b3.complexityLua],
 ]);
 
 // ─── Halstead Rules ───────────────────────────────────────────────────────
@@ -46,6 +47,7 @@ export const HALSTEAD_RULES: Map<string, HalsteadRules> = new Map([
   ['csharp', csharp.halstead],
   ['ruby', ruby.halstead],
   ['php', php.halstead],
+  ['lua', b3.halsteadLua],
 ]);
 
 // ─── CFG Rules ────────────────────────────────────────────────────────────