fix: more robust solution project check for ts < 5.7 in ts plugin (#2758)

#2756

The problem is that in TypeScript before 5.7, the project files were added later than plugin initialisation. Thus, the IsSolution method will always return true in any project using project references during plugin initialisation.

Author: jasonlyu123

packages/typescript-plugin/src/index.ts

@@ -7,8 +7,8 @@ import type ts from 'typescript/lib/tsserverlibrary';
 import { ConfigManager, Configuration } from './config-manager';
 import { ProjectSvelteFilesManager } from './project-svelte-files';
 import {
-    getConfigPathForProject,
     getProjectDirectory,
+    getProjectParsedCommandLine,
     importSvelteCompiler,
     isSvelteProject
 } from './utils';
@@ -47,11 +47,7 @@ function init(modules: { typescript: typeof ts }): ts.server.PluginModule {
             logger.log(info.config);
         }
 
-        // This call the ConfiguredProject.getParsedCommandLine
-        // where it'll try to load the cached version of the parsedCommandLine
-        const parsedCommandLine = info.languageServiceHost.getParsedCommandLine?.(
-            getConfigPathForProject(info.project)
-        );
+        const parsedCommandLine = getProjectParsedCommandLine(info.project);
 
         // For some reason it's no longer enough to patch this at the projectService level, so we do it here, too
         // TODO investigate if we can use the script snapshot for all Svelte files, too, enabling Svelte file

packages/typescript-plugin/src/utils.ts

@@ -260,7 +260,12 @@ export function isSvelteProject(project: ts.server.Project) {
     // The solution project is mostly just a container we don't need to patch it
     // and having any files in this project cause TSServer to send config error while it originally won't
     if ((project as any).isSolution?.()) {
-        return false;
+        // In TypeScript before 5.7, the project files were added later than plugin loading
+        // so we need to also check if the parsedCommandLine includes any files
+        const parsedCommandLine = getProjectParsedCommandLine(project);
+        if (parsedCommandLine?.fileNames.length === 0) {
+            return false;
+        }
     }
 
     const projectDirectory = getProjectDirectory(project);
@@ -313,3 +318,16 @@ export function importSvelteCompiler(
         // ignore
     }
 }
+
+/**
+ * This call the ConfiguredProject.getParsedCommandLine
+ * where it'll try to load the cached version of the parsedCommandLine
+ */
+export function getProjectParsedCommandLine(project: ts.server.Project) {
+    const configPath = getConfigPathForProject(project);
+    const parsedCommandLine = (project as ts.LanguageServiceHost).getParsedCommandLine?.(
+        configPath
+    );
+
+    return parsedCommandLine;
+}