fix path autocompletion trigger logic

Author: legomushroom

src/vs/workbench/contrib/chat/common/promptSyntax/codecs/tokens/fileReference.ts

@@ -56,7 +56,7 @@ export class FileReference extends PromptVariableWithData {
 	 * Get the range of the `link` part of the token (e.g.,
 	 * the `/path/to/file.md` part of `#file:/path/to/file.md`).
 	 */
-	public get linkRange(): IRange {
+	public get linkRange(): IRange | undefined {
 		return super.dataRange;
 	}
 }

src/vs/workbench/contrib/chat/common/promptSyntax/codecs/tokens/promptVariable.ts

@@ -125,17 +125,28 @@ export class PromptVariableWithData extends PromptVariable {
 	/**
 	 * Range of the `data` part of the variable.
 	 */
-	public get dataRange(): IRange {
+	public get dataRange(): IRange | undefined {
 		const { range } = this;
+
+		// calculate the start column number of the `data` part of the variable
 		const dataStartColumn = range.startColumn +
 			START_CHARACTER.length + this.name.length +
 			DATA_SEPARATOR.length;
 
-		return new Range(
+		// create `range` of the `data` part of the variable
+		const result = new Range(
 			range.startLineNumber,
 			dataStartColumn,
 			range.endLineNumber,
 			range.endColumn,
 		);
+
+		// if the resulting range is empty, return `undefined`
+		// because there is no `data` part present in the variable
+		if (result.isEmpty()) {
+			return undefined;
+		}
+
+		return result;
 	}
 }

src/vs/workbench/contrib/chat/common/promptSyntax/languageFeatures/promptPathAutocompletion.ts

@@ -244,21 +244,20 @@ export class PromptPathAutocompletion extends Disposable implements CompletionIt
 		// when character is `:`, there must be no link present yet
 		// otherwise the `:` was used in the middle of the link hence
 		// we don't want to provide suggestions for that
-		if (character === ':' && linkRange !== undefined) {
+		if ((character === ':') && (linkRange !== undefined)) {
 			return [];
 		}
 
 		// otherwise when the `.` character is present, it is inside the link part
 		// of the reference, hence we always expect the link range to be present
-		if (character === '.' && linkRange === undefined) {
+		if ((character === '.') && (linkRange === undefined)) {
 			return [];
 		}
 
 		const suggestions = await this.getFolderSuggestions(fileFolderUri);
 
-		// replacement range of the suggestions
-		// when character is `.` we want to also replace it, because we add
-		// the `./` at the beginning of all the relative paths
+		// replacement range for suggestions; when character is `.`, we want to also
+		// replace it, because we add `./` at the beginning of all the relative paths
 		const startColumnOffset = (character === '.') ? 1 : 0;
 		const range = {
 			...fileReference.range,