test: add

crates/node_binding/src/diagnostic.rs

@@ -78,6 +78,12 @@ pub fn format_diagnostic(diagnostic: JsDiagnostic) -> Result<External<Diagnostic
           "Format diagnostic failed: Invalid `length` in location.",
         ));
       }
+      if !source_code.is_char_boundary(offset) || !source_code.is_char_boundary(end_byte) {
+        return Err(Error::new(
+          Status::Unknown,
+          "Format diagnostic failed: Invalid char boundary. Did you pass the correct line, column and length?",
+        ));
+      }
       d = d.with_label(LabeledSpan::new(location.text, offset, length));
     }
   }

crates/rspack_util/src/location.rs

@@ -42,9 +42,9 @@ pub fn try_line_column_length_to_location(
   let sc = column;
 
   let sb = rope.try_line_to_byte(sl).ok()?;
-  let char_index = rope.try_byte_to_char(sb + sc + length).ok()?;
-  let el = rope.try_char_to_line(char_index).ok()?;
-  let ec = char_index - rope.try_line_to_char(el).ok()?;
+  let end_byte = sb + sc + length;
+  let el = rope.try_byte_to_line(end_byte).ok()?;
+  let ec = end_byte - rope.try_line_to_byte(el).ok()?;
 
   Some(Location {
     sl: sl as u32,

packages/rspack-test-tools/tests/diagnosticsCases/module-build-failed/loader-emit-diagnostic/index.js

@@ -10,3 +10,4 @@ require("!./with-location.js!")
 
 require("!./with-multiple-line.js!")
 
+require("!./with-multi-byte-char.js!")

packages/rspack-test-tools/tests/diagnosticsCases/module-build-failed/loader-emit-diagnostic/stats.err

@@ -41,6 +41,26 @@ ERROR in (./with-location.js!) 1:1-4
    ·  ───
    ╰────
 
+ERROR in (./with-multi-byte-char.js!) 1:0-13
+  × ModuleError: Multi-byte character error
+   ╭────
+ 1 │ 👯‍♀️👯‍♀️👯‍♀️👯‍♀️
+   · ───
+   ╰────
+
+ERROR in (./with-multi-byte-char.js!)
+  × Module build failed:
+  ╰─▶   × Error: Format diagnostic failed: Invalid char boundary. Did you pass the correct line, column and length?
+        │     at xxx
+        │     at xxx
+        │     at xxx
+        │     at xxx
+        │     at xxx
+        │     at xxx
+        │     at xxx
+        │     at xxx
+        │
+
 ERROR in (./with-multiple-line.js!) 1:0-2:4
   × ModuleError: Multiple line error
    ╭─[1:0]

packages/rspack-test-tools/tests/diagnosticsCases/module-build-failed/loader-emit-diagnostic/with-multi-byte-char.js

@@ -0,0 +1,25 @@
+/** @type {import("@rspack/core").LoaderDefinition} */
+module.exports = function() {
+	this.experiments.emitDiagnostic({
+		message: "Multi-byte character error",
+		severity: "error",
+		sourceCode: `👯‍♀️👯‍♀️👯‍♀️👯‍♀️`,
+		location: {
+			line: 1,
+			column: 0,
+			length: 13,
+		},
+	});
+	// Boundary error
+	this.experiments.emitDiagnostic({
+		message: "Multi-byte character error",
+		severity: "error",
+		sourceCode: `"❤️🧡💛💚💙💜"`,
+		location: {
+			line: 1,
+			column: 0,
+			length: 13,
+		},
+	});
+	return ""
+}