improve scorer on file paths

src/vs/base/common/scorer.ts

@@ -45,7 +45,7 @@ BEGIN THIRD PARTY
  * Start of word/path bonus: 7
  * Start of string bonus: 8
  */
-export function _doScore(target: string, query: string): Score {
+export function _doScore(target: string, query: string, inverse?: boolean): Score {
 	if (!target || !query) {
 		return NO_SCORE; // return early if target or query are undefined
 	}
@@ -62,11 +62,25 @@ export function _doScore(target: string, query: string): Score {
 
 	const matchingPositions: number[] = [];
 
-	let index = 0;
-	let startAt = 0;
+	let index: number;
+	let startAt: number;
+	if (!inverse) {
+		index = 0;
+		startAt = 0;
+	} else {
+		index = queryLen - 1; // inverse: from end of query to beginning
+		startAt = target.length - 1; // inverse: from end of target to beginning
+	}
+
 	let score = 0;
-	while (index < queryLen) {
-		let indexOf = targetLower.indexOf(queryLower[index], startAt);
+	while (inverse ? index >= 0 : index < queryLen) {
+		let indexOf: number;
+		if (!inverse) {
+			indexOf = targetLower.indexOf(queryLower[index], startAt);
+		} else {
+			indexOf = targetLower.lastIndexOf(queryLower[index], startAt); // inverse: look from the end
+		}
+
 		if (indexOf < 0) {
 
 			// console.log(`Character not part of target ${query[index]}`);
@@ -120,8 +134,18 @@ export function _doScore(target: string, query: string): Score {
 
 		// console.groupEnd();
 
-		startAt = indexOf + 1;
-		index++;
+		if (!inverse) {
+			startAt = indexOf + 1;
+			index++;
+		} else {
+			startAt = indexOf - 1; // inverse: go to begining from end
+			index--; // inverse: also for query index
+		}
+	}
+
+	// inverse: flip the matching positions so that they appear in order
+	if (inverse) {
+		matchingPositions.reverse();
 	}
 
 	const res: Score = (score > 0) ? [score, matchingPositions] : NO_SCORE;
@@ -248,7 +272,18 @@ function doScoreItem<T>(label: string, description: string, path: string, query:
 		const descriptionPrefixLength = descriptionPrefix.length;
 		const descriptionAndLabel = `${descriptionPrefix}${label}`;
 
-		const [labelDescriptionScore, labelDescriptionPositions] = _doScore(descriptionAndLabel, query);
+		let [labelDescriptionScore, labelDescriptionPositions] = _doScore(descriptionAndLabel, query);
+
+		// Optimize for file paths: score from the back to the beginning to catch more specific folder
+		// names that match on the end of the file. This yields better results in most cases.
+		if (!!path) {
+			const [labelDescriptionScoreInverse, labelDescriptionPositionsInverse] = _doScore(descriptionAndLabel, query, true /* inverse */);
+			if (labelDescriptionScoreInverse && labelDescriptionScoreInverse > labelDescriptionScore) {
+				labelDescriptionScore = labelDescriptionScoreInverse;
+				labelDescriptionPositions = labelDescriptionPositionsInverse;
+			}
+		}
+
 		if (labelDescriptionScore) {
 			const labelDescriptionMatches = createMatches(labelDescriptionPositions);
 			const labelMatch: IMatch[] = [];

src/vs/base/test/common/scorer.test.ts

@@ -79,7 +79,7 @@ suite('Scorer', () => {
 		assert.equal(positions[1], 6);
 	});
 
-	test('scoreFile - matches are proper', function () {
+	test('scoreItem - matches are proper', function () {
 		let res = scorer.scoreItem(null, 'something', ResourceAccessor, cache);
 		assert.ok(!res.score);
 
@@ -151,7 +151,25 @@ suite('Scorer', () => {
 		assert.ok(pathRes.score > noRes.score);
 	});
 
-	test('compareFilesByScore - identity', function () {
+	test('scoreItem - optimize for file paths', function () {
+		const resource = URI.file('/xyz/others/spath/some/xsp/file123.txt');
+
+		// xsp is more relevant to the end of the file path even though it matches
+		// fuzzy also in the beginning. we verify the more relevant match at the
+		// end gets returned.
+		const pathRes = scorer.scoreItem(resource, 'xspfile123', ResourceAccessor, cache);
+		assert.ok(pathRes.score);
+		assert.ok(pathRes.descriptionMatch);
+		assert.ok(pathRes.labelMatch);
+		assert.equal(pathRes.labelMatch.length, 1);
+		assert.equal(pathRes.labelMatch[0].start, 0);
+		assert.equal(pathRes.labelMatch[0].end, 7);
+		assert.equal(pathRes.descriptionMatch.length, 1);
+		assert.equal(pathRes.descriptionMatch[0].start, 23);
+		assert.equal(pathRes.descriptionMatch[0].end, 26);
+	});
+
+	test('compareItemsByScore - identity', function () {
 		const resourceA = URI.file('/some/path/fileA.txt');
 		const resourceB = URI.file('/some/path/other/fileB.txt');
 		const resourceC = URI.file('/unrelated/some/path/other/fileC.txt');