fix: drop 3-char-root meta fallback; rely on expanded ClaML map (Goal 1)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/pipeline.rs

@@ -23,32 +23,39 @@ impl Pipeline {
         Ok(Self { entries, meta, lexical, pool_size: cfg.pool_size })
     }
 
-    /// Look up ICD metadata with fallback: exact code → strip trailing '0' after
-    /// the decimal (e.g. "E11.90" → "E11.9") → 3-char root (e.g. "E11").
-    /// The corpus uses 5- and 6-char codes; ClaML uses 3-, 5-, and 6-char codes.
+    /// Look up ICD metadata: exact code first, then — only for 6-char dotted codes
+    /// of the form `Lxx.yz` — the 5-char parent `Lxx.y`.
+    ///
+    /// The ClaML map (populated by `claml::load`) now contains synthesized
+    /// 5th-digit entries (e.g. `E11.90`, `I10.91`) with correct `Para295 = "P"`,
+    /// so the exact hit succeeds for the vast majority of corpus codes.  The
+    /// 5-char-parent fallback covers any residual gap where a 6-char code is not
+    /// explicitly present but its 5-char parent is.
+    ///
+    /// No 3-char-root fallback is applied: that level caused ~1 193 codes to
+    /// inherit the parent's `Para295 = "V"` and be wrongly dropped under
+    /// `--billable-only` (Goal 1 regression).  Codes absent from ClaML entirely
+    /// yield `None` (accepted, documented out-of-scope gap).
     fn meta_lookup<'a>(&'a self, code: &str) -> Option<&'a IcdMeta> {
         if let Some(m) = self.meta.get(code) {
             return Some(m);
         }
-        // Try stripping a trailing '0' from the last position after the dot
-        // e.g. "E11.90" → "E11.9",  "I10.90" → "I10.9",  "G40.00" → "G40.0"
-        if code.len() >= 5 {
-            if let Some(dot_pos) = code.find('.') {
-                let after_dot = &code[dot_pos + 1..];
-                if after_dot.ends_with('0') && after_dot.len() > 1 {
-                    let trimmed = &code[..code.len() - 1];
-                    if let Some(m) = self.meta.get(trimmed) {
+        // 5-char-parent fallback only for 6-char dotted codes: Lxx.yz → Lxx.y
+        // Pattern: one letter, two digits, dot, two digits (total 6 chars).
+        if code.len() == 6 {
+            let bytes = code.as_bytes();
+            if bytes[0].is_ascii_alphabetic()
+                && bytes[1].is_ascii_digit()
+                && bytes[2].is_ascii_digit()
+                && bytes[3] == b'.'
+                && bytes[4].is_ascii_alphanumeric()
+                && bytes[5].is_ascii_alphanumeric()
+            {
+                if let Some(m) = self.meta.get(&code[..5]) {
                     return Some(m);
                 }
             }
         }
-        }
-        // Fallback to 3-char root (e.g. "E11")
-        if code.len() > 3 {
-            if let Some(m) = self.meta.get(&code[..3]) {
-                return Some(m);
-            }
-        }
         None
     }
 

tests/pipeline_mode_c_tests.rs

@@ -25,3 +25,13 @@ fn billable_only_filter_excludes_three_digit_v_codes() {
     let res = p.suggest("Cholera", Mode::C, &f, 10);
     assert!(res.suggestions.iter().all(|s| s.tags.billable && s.tags.valid));
 }
+
+#[test]
+fn billable_only_keeps_diabetes_5th_digit_codes() {
+    let p = Pipeline::load(&cfg()).unwrap();
+    let f = Filter { billable_only: true, valid_only: true, chapters: None, exclude_exotic: false };
+    let res = p.suggest("Diabetes mellitus Typ 2", Mode::C, &f, 10);
+    assert!(res.suggestions.iter().any(|s| s.icd_code.starts_with("E11") && s.tags.billable),
+        "billable E11.x must survive --billable-only; got {:?}",
+        res.suggestions.iter().map(|s| (&s.icd_code, s.tags.billable)).collect::<Vec<_>>());
+}