Unclear error if line-length goes beyond u16 boundaries

[chirizxc]

Summary

Version

ruff 0.14.0 (beea8cd 2025-10-07)

[chirizxc]

I would expect something like:

❯ git diff
diff --git a/crates/ruff_linter/src/line_width.rs b/crates/ruff_linter/src/line_width.rs
index 7525a68cd..b9d721e71 100644
--- a/crates/ruff_linter/src/line_width.rs
+++ b/crates/ruff_linter/src/line_width.rs
@@ -14,7 +14,7 @@ use ruff_text_size::TextSize;
 /// The length of a line of text that is considered too long.
 ///
 /// The allowed range of values is 1..=320
-#[derive(Clone, Copy, Debug, Eq, PartialEq, serde::Serialize, serde::Deserialize)]
+#[derive(Clone, Copy, Debug, Eq, PartialEq, serde::Serialize)]
 #[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
 pub struct LineLength(
     #[cfg_attr(feature = "schemars", schemars(range(min = 1, max = 320)))] NonZeroU16,
@@ -112,6 +112,21 @@ impl std::fmt::Display for LineLengthFromIntError {
     }
 }
 
+impl<'de> serde::Deserialize<'de> for LineLength {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        let value = u64::deserialize(deserializer)?;
+        let value = u16::try_from(value)
+            .map_err(|_| serde::de::Error::custom(
+                format!("line-length must be between 1 and {} (got {})", Self::MAX, value)
+            ))?;
+
+        Self::try_from(value).map_err(serde::de::Error::custom)
+    }
+}
+
 impl From<LineLength> for u16 {
     fn from(value: LineLength) -> Self {
         value.0.get()

[chirizxc]

I don't really know where numbers larger than 65535 can occur on real projects