chore: provide option to pass Svelte compiler path (#471)

Tooling can use this to work around some Svelte major version differences

Author: dummdidumm

index.d.ts

@@ -6,6 +6,7 @@ export interface PluginConfig {
     svelteBracketNewLine?: boolean;
     svelteAllowShorthand?: boolean;
     svelteIndentScriptAndStyle?: boolean;
+    svelte5CompilerPath?: string;
 }
 
 export type PrettierConfig = PluginConfig & Config;

src/index.ts

@@ -31,9 +31,22 @@ export const languages: Partial<SupportLanguage>[] = [
 export const parsers: Record<string, Parser> = {
     svelte: {
         hasPragma,
-        parse: (text) => {
+        parse: async (text, options: ParserOptions) => {
             try {
-                return <ASTNode>{ ...parse(text), __isRoot: true };
+                let _parse = parse;
+                if (options.svelte5CompilerPath) {
+                    try {
+                        _parse = (await import(options.svelte5CompilerPath)).parse;
+                    } catch (e) {
+                        console.warn(
+                            `Failed to load Svelte 5 compiler from ${options.svelte5CompilerPath}`,
+                        );
+                        console.warn(e);
+                        options.svelte5CompilerPath = undefined;
+                    }
+                }
+
+                return <ASTNode>{ ..._parse(text), __isRoot: true };
             } catch (err: any) {
                 if (err.start != null && err.end != null) {
                     // Prettier expects error objects to have loc.start and loc.end fields.
@@ -57,8 +70,9 @@ export const parsers: Record<string, Parser> = {
             // Therefore we do it ourselves here.
             options.originalText = text;
             // Only Svelte 5 can have TS in the template
-            options._svelte_ts = isSvelte5Plus && result.isTypescript;
-            options._svelte_is5Plus = isSvelte5Plus;
+            const is = !!options.svelte5CompilerPath || isSvelte5Plus;
+            options._svelte_ts = is && result.isTypescript;
+            options._svelte_is5Plus = is;
             return text;
         },
         locStart,

src/options.ts

@@ -19,6 +19,12 @@ function makeChoice(choice: string) {
 }
 
 export const options: Record<keyof PluginConfig, SupportOption> = {
+    svelte5CompilerPath: {
+        category: 'Svelte',
+        type: 'string',
+        default: '',
+        description: 'Only set this when using Svelte 5! Path to the Svelte 5 compiler',
+    },
     svelteSortOrder: {
         category: 'Svelte',
         type: 'choice',