chore(compiler): store byte offsets in wing spans (#6094)

This is a minor improvement that prevents the need to calculate line/column numbers when we're emitting errors for CLI error messages.

## Checklist

- [ ] Title matches [Winglang's style guide](https://www.winglang.io/contributing/start-here/pull_requests#how-are-pull-request-titles-formatted)
- [ ] Description explains motivation and solution
- [ ] Tests added (always)
- [ ] Docs updated (only required for features)
- [ ] Added `pr/e2e-full` label if this feature requires end-to-end testing

*By submitting this pull request, I confirm that my contribution is made under the terms of the [Wing Cloud Contribution License](https://github.com/winglang/wing/blob/main/CONTRIBUTION_LICENSE.md)*.

apps/wing-console/console/server/src/utils/format-wing-error.ts

@@ -6,16 +6,6 @@ import { prettyPrintError } from "@winglang/sdk/lib/util/enhanced-error";
 import type { File, Label } from "codespan-wasm";
 import { CHARS_ASCII, emitDiagnostic } from "codespan-wasm";
 
-function offsetFromLineAndColumn(source: string, line: number, column: number) {
-  const lines = source.split("\n");
-  let offset = 0;
-  for (let index = 0; index < line; index++) {
-    offset += lines[index]!.length + 1;
-  }
-  offset += column;
-  return offset;
-}
-
 export const formatWingError = async (error: unknown, entryPoint?: string) => {
   try {
     if (error instanceof CompileError) {
@@ -33,16 +23,8 @@ export const formatWingError = async (error: unknown, entryPoint?: string) => {
         if (span !== null && span !== undefined && span.file_id) {
           // `span` should only be null if source file couldn't be read etc.
           const source = await readFile(span.file_id, "utf8");
-          const start = offsetFromLineAndColumn(
-            source,
-            span.start.line,
-            span.start.col,
-          );
-          const end = offsetFromLineAndColumn(
-            source,
-            span.end.line,
-            span.end.col,
-          );
+          const start = span.start_offset;
+          const end = span.end_offset;
           const filePath = relative(cwd, span.file_id);
           files.push({ name: filePath, source });
           labels.push({
@@ -60,16 +42,8 @@ export const formatWingError = async (error: unknown, entryPoint?: string) => {
             continue;
           }
           const source = await readFile(annotation.span.file_id, "utf8");
-          const start = offsetFromLineAndColumn(
-            source,
-            annotation.span.start.line,
-            annotation.span.start.col,
-          );
-          const end = offsetFromLineAndColumn(
-            source,
-            annotation.span.end.line,
-            annotation.span.end.col,
-          );
+          const start = annotation.span.start_offset;
+          const end = annotation.span.end_offset;
           const filePath = relative(cwd, annotation.span.file_id);
           files.push({ name: filePath, source });
           labels.push({

apps/wing/src/commands/compile.ts

@@ -103,8 +103,8 @@ export async function compile(entrypoint?: string, options?: CompileOptions): Pr
         if (span?.file_id) {
           // `span` should only be null if source file couldn't be read etc.
           const source = await fsPromise.readFile(span.file_id, "utf8");
-          const start = byteOffsetFromLineAndColumn(source, span.start.line, span.start.col);
-          const end = byteOffsetFromLineAndColumn(source, span.end.line, span.end.col);
+          const start = span.start_offset;
+          const end = span.end_offset;
           const filePath = relative(cwd, span.file_id);
           files.push({ name: filePath, source });
           labels.push({
@@ -122,16 +122,8 @@ export async function compile(entrypoint?: string, options?: CompileOptions): Pr
             continue;
           }
           const source = await fsPromise.readFile(annotation.span.file_id, "utf8");
-          const start = byteOffsetFromLineAndColumn(
-            source,
-            annotation.span.start.line,
-            annotation.span.start.col
-          );
-          const end = byteOffsetFromLineAndColumn(
-            source,
-            annotation.span.end.line,
-            annotation.span.end.col
-          );
+          const start = annotation.span.start_offset;
+          const end = annotation.span.end_offset;
           const filePath = relative(cwd, annotation.span.file_id);
           files.push({ name: filePath, source });
           labels.push({
@@ -179,16 +171,3 @@ export async function compile(entrypoint?: string, options?: CompileOptions): Pr
     }
   }
 }
-
-function byteOffsetFromLineAndColumn(source: string, line: number, column: number) {
-  const lines = source.split("\n");
-  let offset = 0;
-  for (let i = 0; i < line; i++) {
-    offset += lines[i].length + 1;
-  }
-
-  // Convert char offset to byte offset
-  const encoder = new TextEncoder();
-  const srouce_bytes = encoder.encode(source.substring(0, offset));
-  return srouce_bytes.length + column;
-}

libs/wingc/src/diagnostic.rs

@@ -92,6 +92,10 @@ pub struct WingSpan {
 	pub end: WingLocation,
 	/// Relative path to the file based on the entrypoint file
 	pub file_id: String,
+	/// Byte-level offsets into the file.
+	/// Not used for comparisons (start/end are used instead)
+	pub start_offset: usize,
+	pub end_offset: usize,
 }
 
 impl WingSpan {
@@ -213,10 +217,23 @@ impl WingSpan {
 			other.start
 		};
 		let end = if self.end > other.end { self.end } else { other.end };
+		let start_offset = if self.start_offset < other.start_offset {
+			self.start_offset
+		} else {
+			other.start_offset
+		};
+		let end_offset = if self.end_offset > other.end_offset {
+			self.end_offset
+		} else {
+			other.end_offset
+		};
+
 		Self {
 			start,
 			end,
 			file_id: self.file_id.clone(),
+			start_offset,
+			end_offset,
 		}
 	}
 
@@ -433,6 +450,8 @@ mod tests {
 			start: WingLocation { line: 0, col: 0 },
 			end: WingLocation { line: 1, col: 10 },
 			file_id: "test".to_string(),
+			start_offset: 0,
+			end_offset: 10,
 		};
 
 		let in_position = Position { line: 0, character: 5 };
@@ -450,17 +469,23 @@ mod tests {
 			start: WingLocation { line: 0, col: 0 },
 			end: WingLocation { line: 1, col: 10 },
 			file_id: file_id.to_string(),
+			start_offset: 0,
+			end_offset: 10,
 		};
 
 		let in_span = WingSpan {
 			start: WingLocation { line: 0, col: 5 },
 			end: WingLocation { line: 1, col: 5 },
 			file_id: file_id.to_string(),
+			start_offset: 0,
+			end_offset: 10,
 		};
 		let out_span = WingSpan {
 			start: WingLocation { line: 2, col: 0 },
 			end: WingLocation { line: 2, col: 5 },
 			file_id: file_id.to_string(),
+			start_offset: 0,
+			end_offset: 10,
 		};
 
 		assert!(span.contains_span(&in_span));
@@ -473,6 +498,8 @@ mod tests {
 			start: WingLocation { line: 0, col: 0 },
 			end: WingLocation { line: 1, col: 10 },
 			file_id: "test".to_string(),
+			start_offset: 0,
+			end_offset: 10,
 		};
 
 		let in_location = WingLocation { line: 0, col: 5 };
@@ -488,6 +515,8 @@ mod tests {
 			start: WingLocation { line: 1, col: 5 },
 			end: WingLocation { line: 1, col: 10 },
 			file_id: "test".to_string(),
+			start_offset: 0,
+			end_offset: 10,
 		};
 
 		let like_span1 = span1.clone();
@@ -496,11 +525,15 @@ mod tests {
 			start: WingLocation { line: 0, col: 0 },
 			end: WingLocation { line: 1, col: 1 },
 			file_id: "test".to_string(),
+			start_offset: 0,
+			end_offset: 10,
 		};
 		let later = WingSpan {
 			start: WingLocation { line: 2, col: 0 },
 			end: WingLocation { line: 2, col: 5 },
 			file_id: "test".to_string(),
+			start_offset: 0,
+			end_offset: 10,
 		};
 
 		assert!(span1 == like_span1);

libs/wingc/src/jsify/codemaker.rs

@@ -380,6 +380,8 @@ mod tests {
 			file_id: "test.w".to_string(),
 			start: WingLocation { line: 2, col: 4 },
 			end: WingLocation { line: 2, col: 8 },
+			start_offset: 0,
+			end_offset: 0,
 		};
 		let mut code = CodeMaker::with_source(&base_span);
 		code.line("1");
@@ -415,6 +417,8 @@ mod tests {
 			file_id: "test.w".to_string(),
 			start: WingLocation { line: 2, col: 4 },
 			end: WingLocation { line: 2, col: 8 },
+			start_offset: 0,
+			end_offset: 0,
 		};
 		let mut code = CodeMaker::with_source(&base_span);
 		code.line("1");

libs/wingc/src/lsp/completions.rs

@@ -179,11 +179,15 @@ pub fn on_completion(params: lsp_types::CompletionParams) -> CompletionResponse
 					start: parent.start_position().into(),
 					end: parent.end_position().into(),
 					file_id: file.to_string(),
+					start_offset: parent.start_byte(),
+					end_offset: parent.end_byte(),
 				}),
 				WingSpan {
 					start: node_to_complete.start_position().into(),
 					end: node_to_complete.end_position().into(),
 					file_id: file.to_string(),
+					start_offset: node_to_complete.start_byte(),
+					end_offset: node_to_complete.end_byte(),
 				},
 				params.text_document_position.position.into(),
 				&root_scope,

libs/wingc/src/parser.rs

@@ -565,6 +565,8 @@ impl<'s> Parser<'s> {
 			start: node_range.start_point.into(),
 			end: node_range.end_point.into(),
 			file_id: self.source_name.to_string(),
+			start_offset: node_range.start_byte,
+			end_offset: node_range.end_byte,
 		}
 	}
 

libs/wingc/src/type_check.rs

@@ -5473,11 +5473,19 @@ impl<'a> TypeChecker<'a> {
 		let start = root.span.start;
 		let end = path.last().map(|s| s.span.end).unwrap_or(root.span.end);
 		let file_id = root.span.file_id.clone();
+		let start_offset = root.span.start_offset;
+		let end_offset = path.last().map(|s| s.span.end_offset).unwrap_or(root.span.end_offset);
 
 		Some(UserDefinedType {
 			root,
 			fields: path,
-			span: WingSpan { start, end, file_id },
+			span: WingSpan {
+				start,
+				end,
+				file_id,
+				start_offset,
+				end_offset,
+			},
 		})
 	}
 

libs/wingcompiler/src/wingc.ts

@@ -188,7 +188,7 @@ export async function load(options: WingCompilerLoadOptions) {
     wasi_snapshot_preview1: wasi.wasiImport,
     env: {
       // This function is used only by the lsp
-      send_diagnostic: () => { },
+      send_diagnostic: () => {},
     },
     ...(options.imports ?? {}),
   } as any;
@@ -222,34 +222,28 @@ const HIGH_MASK = BigInt(32);
 // From diagnostic.rs
 export interface WingDiagnostic {
   message: string;
-  span?: {
-    start: {
-      line: number;
-      col: number;
-    };
-    end: {
-      line: number;
-      col: number;
-    };
-    file_id: string;
-  };
+  span?: WingSpan;
   annotations: {
     message: string;
-    span: {
-      start: {
-        line: number;
-        col: number;
-      };
-      end: {
-        line: number;
-        col: number;
-      };
-      file_id: string;
-    };
+    span: WingSpan;
   }[];
   hints: string[];
 }
 
+export interface WingSpan {
+  start: {
+    line: number;
+    col: number;
+  };
+  end: {
+    line: number;
+    col: number;
+  };
+  file_id: string;
+  start_offset: number;
+  end_offset: number;
+}
+
 /**
  * Runs the given WASM function in the Wing Compiler WASM instance.
  *
@@ -282,7 +276,7 @@ export function invoke(
     argMemoryBuffer.set(bytes);
 
     const result = exports[func](argPointer, bytes.byteLength);
-    
+
     if (result === 0 || result === undefined || result === 0n) {
       return 0;
     } else {