fix: implement getScriptSnapshot only for file to format

Should solve the performance regression introduced when fixing #64.

Fixes #67.

.github/workflows/test.yml

@@ -20,4 +20,4 @@ jobs:
         with:
           node-version: ${{ matrix.node }}
       - run: npm install
-      - run: npm test -- --timeout=1m
+      - run: npm test

lib/service-host.js

@@ -29,17 +29,8 @@ const getLanguageServiceHost = (path, content) => {
 		getScriptVersion: () => '0',
 		getScriptSnapshot: (filePath) => {
 			if (filePath === path) {
-				// for perf, but also needed to make the tests pass because there are no real files involved
 				return ts.ScriptSnapshot.fromString(content);
 			}
-
-			if (ts.sys.fileExists(filePath)) {
-				const fileContent = ts.sys.readFile(filePath);
-
-				if (fileContent) {
-					return ts.ScriptSnapshot.fromString(fileContent);
-				}
-			}
 		},
 	};
 };