fix: support SvelteKit zero-types with svelte-check --incremental (#2939)

- add jsdoc-type variants for SvelteKit transform helpers
- use those helpers in svelte-check to transform files. Transformed files are written into the generated folder
- filter out diagnostics of original files which have a transformed sibling; sometimes those original files end up in the TS module graph
- remove unused map generation along the way and simplify/deduplicate a few things

Author: dummdidumm

.changeset/stupid-adults-worry.md

@@ -0,0 +1,7 @@
+---
+'svelte-language-server': patch
+'svelte-check': patch
+'svelte2tsx': patch
+---
+
+fix: support SvelteKit zero types in svelte-check --incremental

packages/language-server/src/index.ts

@@ -1,5 +1,5 @@
 export * from './server';
-export { offsetAt } from './lib/documents';
+export { offsetAt, positionAt, getLineOffsets } from './lib/documents';
 export {
     mapSvelteCheckDiagnostics,
     SvelteCheck,

packages/language-server/src/plugins/typescript/DocumentSnapshot.ts

@@ -71,6 +71,7 @@ export interface SvelteSnapshotOptions {
     version: string | undefined;
     transformOnTemplateError: boolean;
     typingsNamespace: string;
+    emitJsDoc?: boolean;
 }
 
 const ambientPathPattern = /node_modules[\/\\]svelte[\/\\]types[\/\\]ambient\.d\.ts$/;
@@ -211,7 +212,8 @@ function preprocessSvelteFile(document: Document, options: SvelteSnapshotOptions
             namespace: document.config?.compilerOptions?.namespace,
             accessors:
                 document.config?.compilerOptions?.accessors ??
-                document.config?.compilerOptions?.customElement
+                document.config?.compilerOptions?.customElement,
+            emitJsDoc: options.emitJsDoc
         });
         text = tsx.code;
         tsxMap = tsx.map as EncodedSourceMap;

packages/language-server/src/plugins/typescript/features/DiagnosticsProvider.ts

@@ -70,16 +70,17 @@ export class DiagnosticsProviderImpl implements DiagnosticsProvider {
             return [];
         }
 
-        const isTypescript =
-            tsDoc.scriptKind === ts.ScriptKind.TSX || tsDoc.scriptKind === ts.ScriptKind.TS;
-
         // Document preprocessing failed, show parser error instead
         if (tsDoc.parserError) {
             return [
                 {
                     range: tsDoc.parserError.range,
                     severity: DiagnosticSeverity.Error,
-                    source: isTypescript ? 'ts' : 'js',
+                    source:
+                        tsDoc.scriptKind === ts.ScriptKind.TSX ||
+                        tsDoc.scriptKind === ts.ScriptKind.TS
+                            ? 'ts'
+                            : 'js',
                     message: tsDoc.parserError.message,
                     code: tsDoc.parserError.code
                 }
@@ -101,7 +102,7 @@ export class DiagnosticsProviderImpl implements DiagnosticsProvider {
             diagnostics.push(...checker.call(lang, tsDoc.filePath));
         }
 
-        return mapAndFilterDiagnostics(diagnostics, document, tsDoc, isTypescript, lang);
+        return mapAndFilterDiagnostics(diagnostics, document, tsDoc, lang);
     }
 
     private async getLSAndTSDoc(document: Document) {
@@ -113,7 +114,6 @@ export function mapAndFilterDiagnostics(
     diagnostics: ts.Diagnostic[],
     document: Document,
     tsDoc: SvelteDocumentSnapshot,
-    isTypescript: boolean,
     lang?: ts.LanguageService
 ): Diagnostic[] {
     const notGenerated = isNotGenerated(tsDoc.getFullText());
@@ -160,6 +160,10 @@ export function mapAndFilterDiagnostics(
         diagnostics = resolveNoopsInReactiveStatements(lang, diagnostics);
     }
 
+    const source =
+        tsDoc.scriptKind === ts.ScriptKind.TSX || tsDoc.scriptKind === ts.ScriptKind.TS
+            ? 'ts'
+            : 'js';
     const mapRange = rangeMapper(tsDoc, document, lang);
     const noFalsePositive = isNoFalsePositive(document, tsDoc);
     const converted: Diagnostic[] = [];
@@ -168,7 +172,7 @@ export function mapAndFilterDiagnostics(
         let diagnostic: Diagnostic = {
             range: convertRange(tsDoc, tsDiag),
             severity: mapSeverity(tsDiag.category),
-            source: isTypescript ? 'ts' : 'js',
+            source,
             message: ts.flattenDiagnosticMessageText(tsDiag.messageText, '\n'),
             code: tsDiag.code,
             tags: getDiagnosticTag(tsDiag)

packages/language-server/src/svelte-check.ts

@@ -29,18 +29,18 @@ import { groupBy } from 'lodash';
 export function mapSvelteCheckDiagnostics(
     sourcePath: string,
     sourceText: string,
-    isTsFile: boolean,
     tsDiagnostics: ts.Diagnostic[]
 ): Diagnostic[] {
     const document = new Document(pathToUrl(sourcePath), sourceText);
     const snapshot = DocumentSnapshot.fromDocument(document, {
         parse: document.compiler?.parse,
         version: document.compiler?.VERSION,
         transformOnTemplateError: false,
-        typingsNamespace: 'svelteHTML'
+        typingsNamespace: 'svelteHTML',
+        emitJsDoc: true
     } satisfies SvelteSnapshotOptions) as SvelteDocumentSnapshot;
 
-    return mapAndFilterDiagnostics(tsDiagnostics, document, snapshot, isTsFile, undefined);
+    return mapAndFilterDiagnostics(tsDiagnostics, document, snapshot);
 }
 
 export type SvelteCheckDiagnosticSource = 'js' | 'css' | 'svelte';