From 824310e6117e3b728ba9db67d6127e85a1ab5f25 Mon Sep 17 00:00:00 2001
From: "Dylan M. Taylor" <dylan@dylanmtaylor.com>
Date: Tue, 3 Nov 2026 11:47:15 +0000
Subject: [PATCH] fix: brush and library names number repeats without
 rescanning

---
 crates/brush/src/lib.rs            |  7 +++----
 crates/engine/src/cmd/library.rs   |  9 ++++++++-
 crates/engine/src/tests/library.rs | 12 ++++++++++++
 3 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/crates/brush/src/lib.rs b/crates/brush/src/lib.rs
index bc75f09cf..40225c054 100644
--- a/crates/brush/src/lib.rs
+++ b/crates/brush/src/lib.rs
@@ -781,10 +781,9 @@ pub fn unique_name(lib: &[Brush], base: &str) -> String {
         return base.to_string();
     }
     // At most `lib.len()` names are taken, so one of the first `lib.len() + 1` candidates is free.
-    (2..=lib.len() + 2)
-        .map(|i| format!("{base} {i}"))
-        .find(|n| !lib.iter().any(|b| &b.name == n))
-        .unwrap_or_else(|| format!("{base} {}", lib.len() + 2))
+    // Each is looked up in a set: scanning the library per candidate is quadratic in its size.
+    let taken: std::collections::HashSet<&str> = lib.iter().map(|b| b.name.as_str()).collect();
+    (2..=lib.len() + 2).map(|i| format!("{base} {i}")).find(|n| !taken.contains(n.as_str())).unwrap_or_else(|| format!("{base} {}", lib.len() + 2))
 }
 
 // ---------- geometry ----------
diff --git a/crates/engine/src/cmd/library.rs b/crates/engine/src/cmd/library.rs
index 70aa9561f..49865914e 100644
--- a/crates/engine/src/cmd/library.rs
+++ b/crates/engine/src/cmd/library.rs
@@ -448,6 +448,8 @@ fn clip(name: &mut String) {
 fn uniquify<'a>(names: impl Iterator<Item = &'a mut String>, fallback: &str, sep: &str, fold: bool) {
     let key = |n: &str| if fold { n.to_lowercase() } else { n.to_string() };
     let mut seen = HashSet::new();
+    // Per repeated name, the number to try next: a run of one name counts on instead of from 2.
+    let mut next: std::collections::HashMap<String, usize> = std::collections::HashMap::new();
     for name in names {
         clip(name);
         if name.trim().is_empty() {
@@ -455,7 +457,12 @@ fn uniquify<'a>(names: impl Iterator<Item = &'a mut String>, fallback: &str, sep
         }
         if seen.contains(&key(name)) {
             let base = name.clone();
-            *name = (2..).map(|n| format!("{base}{sep}{n}")).find(|n| !seen.contains(&key(n))).unwrap_or_default();
+            let n = next.entry(key(&base)).or_insert(2);
+            while seen.contains(&key(&format!("{base}{sep}{n}"))) {
+                *n += 1;
+            }
+            *name = format!("{base}{sep}{n}");
+            *n += 1;
         }
         seen.insert(key(name));
     }
diff --git a/crates/engine/src/tests/library.rs b/crates/engine/src/tests/library.rs
index 92c780e29..a9bafc540 100644
--- a/crates/engine/src/tests/library.rs
+++ b/crates/engine/src/tests/library.rs
@@ -821,6 +821,18 @@ fn imported_libraries_are_made_consistent() {
     );
 }
 
+/// A library of one name repeated as often as it may hold numbers the copies in one pass.
+#[test]
+fn a_library_of_one_repeated_name_imports_numbered() {
+    let mut s = session();
+    let red = json!({"name": "Red", "color": {"model": "rgb", "r": 1, "g": 0, "b": 0}});
+    let lib = json!({"name": "Many", "colors": vec![red; 10_000]});
+    run(&mut s, "library.import", json!({"data": lib.to_string()}));
+    let got = run(&mut s, "library.get", json!({}));
+    let colors = got["colors"].as_array().unwrap();
+    assert_eq!((colors.len(), colors[1]["name"].as_str(), colors[9_999]["name"].as_str()), (10_000, Some("Red 2"), Some("Red 10000")));
+}
+
 #[cfg(not(target_arch = "wasm32"))]
 #[test]
 fn a_library_is_exported_to_a_file_and_imported_from_it() {