fix(callers): cross-project fallback for cora callers (#381)

src/index/graph.rs

@@ -136,6 +136,38 @@ pub fn find_callers(
     Ok(rows.filter_map(|r| r.ok()).collect())
 }
 
+/// Find callers of a symbol across ALL projects (cross-project fallback).
+///
+/// Used when project-scoped `find_callers` returns empty — the symbol may
+/// exist in another indexed project. Returns results with the project root
+/// path so the caller can display which project the match came from.
+pub fn find_callers_cross_project(
+    conn: &Connection,
+    symbol_name: &str,
+    limit: usize,
+) -> anyhow::Result<Vec<CrossProjectCallerResult>> {
+    let pattern = format!("%{symbol_name}%");
+
+    let mut stmt = conn.prepare(
+        "SELECT DISTINCT cg.caller, cg.file, cg.line, p.root_path
+         FROM call_graph cg
+         JOIN projects p ON cg.project_id = p.id
+         WHERE cg.callee LIKE ?1
+         LIMIT ?2",
+    )?;
+
+    let rows = stmt.query_map(rusqlite::params![pattern, limit as i64], |row| {
+        Ok(CrossProjectCallerResult {
+            caller: row.get(0)?,
+            file: row.get(1)?,
+            line: row.get::<_, i64>(2)? as u32,
+            project_root: row.get(3)?,
+        })
+    })?;
+
+    Ok(rows.filter_map(|r| r.ok()).collect())
+}
+
 /// Find all callees of a symbol (what does this call?), scoped to a project.
 ///
 /// Returns symbols that are called by the given name.
@@ -231,6 +263,15 @@ pub struct CallerResult {
     pub line: u32,
 }
 
+/// A cross-project caller result (includes which project the caller belongs to).
+#[derive(Debug, Clone, serde::Serialize)]
+pub struct CrossProjectCallerResult {
+    pub caller: String,
+    pub file: String,
+    pub line: u32,
+    pub project_root: String,
+}
+
 /// A callee result entry.
 #[allow(dead_code)]
 #[derive(Debug, Clone, serde::Serialize)]
@@ -583,6 +624,58 @@ mod tests {
         assert!(names.contains(&"handler"));
     }
 
+    #[test]
+    fn test_find_callers_cross_project() {
+        let conn = mem_conn();
+        let project_a =
+            super::super::schema::get_or_create_project(&conn, "/tmp/project-a").unwrap();
+        let project_b =
+            super::super::schema::get_or_create_project(&conn, "/tmp/project-b").unwrap();
+
+        // Store edges in project A
+        store_edges(
+            &conn,
+            &[CallEdge {
+                caller: "handler_a".to_string(),
+                callee: "shared_util".to_string(),
+                file: "handler.rs".to_string(),
+                line: 5,
+            }],
+            project_a,
+        )
+        .unwrap();
+
+        // Store edges in project B
+        store_edges(
+            &conn,
+            &[CallEdge {
+                caller: "handler_b".to_string(),
+                callee: "shared_util".to_string(),
+                file: "lib.rs".to_string(),
+                line: 10,
+            }],
+            project_b,
+        )
+        .unwrap();
+
+        // Scoped to project A: only finds handler_a
+        let scoped = find_callers(&conn, project_a, "shared_util", 10).unwrap();
+        assert_eq!(scoped.len(), 1);
+        assert_eq!(scoped[0].caller, "handler_a");
+
+        // Scoped to project B: only finds handler_b
+        let scoped_b = find_callers(&conn, project_b, "shared_util", 10).unwrap();
+        assert_eq!(scoped_b.len(), 1);
+        assert_eq!(scoped_b[0].caller, "handler_b");
+
+        // Cross-project: finds BOTH
+        let cross = find_callers_cross_project(&conn, "shared_util", 10).unwrap();
+        assert_eq!(cross.len(), 2);
+        let roots: Vec<&str> = cross.iter().map(|c| c.project_root.as_str()).collect();
+        assert!(roots.contains(&"/tmp/project-a"));
+        assert!(roots.contains(&"/tmp/project-b"));
+    }
+
     #[test]
     fn test_find_callees() {
         let conn = mem_conn();

src/main.rs

@@ -769,8 +769,51 @@ async fn main() -> Result<()> {
             let project_id = index::ensure_project(&conn, &project_root)?;
             let callers = index::graph::find_callers(&conn, project_id, &symbol, limit)?;
 
+            // Cross-project fallback: if no callers in current project,
+            // search across all indexed projects.
+            let cross_project_results = if callers.is_empty() {
+                let cp = index::graph::find_callers_cross_project(&conn, &symbol, limit)?;
+                if !cp.is_empty() {
+                    if !json {
+                        eprintln!(
+                            "{}",
+                            format!(
+                                "No callers in current project. Found {} in other project(s):",
+                                cp.len()
+                            )
+                            .yellow()
+                        );
+                    }
+                    Some(cp)
+                } else {
+                    None
+                }
+            } else {
+                None
+            };
+
             if json {
-                println!("{}", serde_json::to_string_pretty(&callers)?);
+                if let Some(ref cp) = cross_project_results {
+                    println!("{}", serde_json::to_string_pretty(cp)?);
+                } else {
+                    println!("{}", serde_json::to_string_pretty(&callers)?);
+                }
+            } else if callers.is_empty() && cross_project_results.is_some() {
+                let cp = cross_project_results.as_ref().unwrap();
+                println!(
+                    "{}",
+                    format!("Callers of '{symbol}' ({}):", cp.len()).cyan()
+                );
+                println!("{}", "─".repeat(50).dimmed());
+                for c in cp {
+                    println!(
+                        "  {} {}:{}  {}",
+                        c.caller.white().bold(),
+                        c.file.dimmed(),
+                        c.line,
+                        c.project_root.dimmed().italic(),
+                    );
+                }
             } else if callers.is_empty() {
                 eprintln!("{}", format!("No callers found for '{symbol}'.").yellow());
             } else {