Use built-in source map support for determining snapshot location

Incidentally, this means the snap file is now properly tracked as a
dependency.

lib/runner.js

@@ -34,16 +34,6 @@ export default class Runner extends Emittery {
 		this.boundCompareTestSnapshot = this.compareTestSnapshot.bind(this);
 		this.boundSkipSnapshot = this.skipSnapshot.bind(this);
 		this.interrupted = false;
-		this.snapshots = loadSnapshots({
-			file: this.file,
-			fixedLocation: this.snapshotDir,
-			projectDir: this.projectDir,
-			recordNewSnapshots: this.recordNewSnapshots,
-			updating: this.updateSnapshots,
-		});
-		if (this.snapshots.snapPath !== undefined) {
-			this.emit('dependency', this.snapshots.snapPath);
-		}
 
 		this.nextTaskIndex = 0;
 		this.tasks = {
@@ -203,6 +193,29 @@ export default class Runner extends Emittery {
 		}, meta);
 	}
 
+	get snapshots() {
+		if (this._snapshots) {
+			return this._snapshots;
+		}
+
+		// Lazy load not when the runner is instantiated but when snapshots are
+		// needed. This should be after the test file has been loaded and source
+		// maps are available.
+		const snapshots = loadSnapshots({
+			file: this.file,
+			fixedLocation: this.snapshotDir,
+			projectDir: this.projectDir,
+			recordNewSnapshots: this.recordNewSnapshots,
+			updating: this.updateSnapshots,
+		});
+		if (snapshots.snapPath !== undefined) {
+			this.emit('dependency', snapshots.snapPath);
+		}
+
+		this._snapshots = snapshots;
+		return snapshots;
+	}
+
 	compareTestSnapshot(options) {
 		return this.snapshots.compare(options);
 	}

lib/snapshot-manager.js

@@ -1,12 +1,13 @@
 import {Buffer} from 'node:buffer';
 import crypto from 'node:crypto';
 import fs from 'node:fs';
+import {findSourceMap} from 'node:module';
 import path from 'node:path';
+import {fileURLToPath} from 'node:url';
 import zlib from 'node:zlib';
 
 import cbor from 'cbor';
 import concordance from 'concordance';
-import convertSourceMap from 'convert-source-map';
 import indentString from 'indent-string';
 import mem from 'mem';
 import slash from 'slash';
@@ -384,21 +385,17 @@ class Manager {
 }
 
 const resolveSourceFile = mem(file => {
-	const testDir = path.dirname(file);
-	const buffer = tryRead(file);
-	if (!buffer) {
-		return file; // Assume the file is stubbed in our test suite.
+	const sourceMap = findSourceMap(file);
+	if (sourceMap === undefined) {
+		return file;
 	}
 
-	const source = buffer.toString();
-	const converter = convertSourceMap.fromSource(source) || convertSourceMap.fromMapFileSource(source, testDir);
-	if (converter) {
-		const map = converter.toObject();
-		const firstSource = `${map.sourceRoot || ''}${map.sources[0]}`;
-		return path.resolve(testDir, firstSource);
+	const {payload} = sourceMap;
+	if (payload.sources.length === 0) { // Hypothetical?
+		return file;
 	}
 
-	return file;
+	return fileURLToPath(payload.sources[0]);
 });
 
 export const determineSnapshotDir = mem(({file, fixedLocation, projectDir}) => {

package.json

@@ -88,7 +88,6 @@
 		"code-excerpt": "^3.0.0",
 		"common-path-prefix": "^3.0.0",
 		"concordance": "^5.0.4",
-		"convert-source-map": "^1.8.0",
 		"currently-unhandled": "^0.4.1",
 		"debug": "^4.3.2",
 		"del": "^6.0.0",

test-tap/api.js

@@ -463,7 +463,7 @@ for (const opt of opts) {
 			plan.status.on('stateChange', evt => {
 				if (evt.type === 'dependencies') {
 					t.ok(testFiles.has(evt.testFile));
-					t.strictSame(evt.dependencies.slice(-3), sourceFiles);
+					t.strictSame(evt.dependencies.filter(dep => !dep.endsWith('.snap')).slice(-3), sourceFiles);
 				}
 			});
 		});