fix: properly transform invalid identifiers

src/compiler/pre-transform/codemods/legacy-story.test.ts

@@ -188,6 +188,28 @@ describe(transformLegacyStory.name, () => {
     ).toMatchInlineSnapshot(`"<Story name="Default" children={someTemplate} />"`);
   });
 
+  it("transforms 'template' prop to 'children' and text expression becomes expression tag with identifier to snippet (case with invalid identifier)", async ({
+    expect,
+  }) => {
+    const code = `
+      <script context="module">
+        import { Story } from "@storybook/addon-svelte-csf";
+      </script>
+
+      <Story name="Default" template="some template with non valid idenitifier" />
+    `;
+    const component = await parseAndExtractSvelteNode<SvelteAST.Component>(code, 'Component');
+
+    expect(
+      print(
+        transformLegacyStory({
+          component,
+          state: { componentIdentifierName: {} },
+        })
+      )
+    ).toMatchInlineSnapshot(`"<Story name="Default" children={template_c0gseq} />"`);
+  });
+
   it("when directive 'let:args' is used then it wraps Story fragment with 'children' snippet block", async ({
     expect,
   }) => {

src/compiler/pre-transform/codemods/legacy-story.ts

@@ -1,5 +1,3 @@
-import { camelCase } from 'es-toolkit/string';
-
 import {
   createASTArrayExpression,
   createASTAttribute,
@@ -11,6 +9,7 @@ import {
 } from '$lib/parser/ast.js';
 import { InvalidTemplateAttribute } from '$lib/utils/error/legacy-api/index.js';
 
+import { hashTemplateName } from '#utils/identifier-utils';
 import type { State } from '..';
 
 interface Params {
@@ -253,7 +252,7 @@ function templateToChildren(
     value: [
       createASTExpressionTag({
         type: 'Identifier',
-        name: camelCase(
+        name: hashTemplateName(
           value[0].type === 'Text'
             ? value[0].data
             : ((value[0].expression as ESTreeAST.Literal).value as string)

src/compiler/pre-transform/codemods/template-to-snippet.test.ts

@@ -46,6 +46,27 @@ describe(transformTemplateToSnippet.name, () => {
 		`);
   });
 
+  it("covers a case with provided prop 'id' and prop `id` not being a valid identifier", async ({
+    expect,
+  }) => {
+    const code = `
+      <script context="module" lang="ts">
+        import { Template } from "${pkg.name}";
+      </script>
+
+      <Template id="cool-template" let:args>
+        <Button {...args} variant="primary" />
+      </Template>
+    `;
+    const component = await parseAndExtractSvelteNode<SvelteAST.Component>(code, 'Component');
+
+    expect(print(transformTemplateToSnippet({ component }))).toMatchInlineSnapshot(`
+      "{#snippet template_haitqt(args)}
+      	<Button {...args} variant="primary" />
+      {/snippet}"
+    `);
+  });
+
   it("works with 'let:context' directive", async ({ expect }) => {
     const code = `
       <script context="module" lang="ts">

src/compiler/pre-transform/codemods/template-to-snippet.ts

@@ -1,5 +1,6 @@
 import { getStringValueFromAttribute } from '$lib/parser/analyse/story/attributes.js';
 import type { SvelteAST } from '$lib/parser/ast.js';
+import { hashTemplateName } from '$lib/utils/identifier-utils';
 
 interface Params {
   component: SvelteAST.Component;
@@ -70,7 +71,7 @@ export function transformTemplateToSnippet(params: Params): SvelteAST.SnippetBlo
     type: 'SnippetBlock',
     expression: {
       type: 'Identifier',
-      name: id ?? 'sb_default_template',
+      name: id ? hashTemplateName(id) : 'sb_default_template',
     },
     parameters,
     body: fragment,

src/utils/identifier-utils.ts

@@ -54,3 +54,23 @@ export const isValidVariableName = (str: string) => {
 
   return true;
 };
+
+/**
+ * Function to convert a non valid string template name to a valid identifier preventing
+ * clashing with other templates with similar names.
+ *
+ * Stolen with 🧡 from the svelte codebase by @paoloricciuti
+ *
+ * @param str the template name
+ * @returns a hash based on the content of the initial string which is a valid identifier
+ */
+export function hashTemplateName(str: string) {
+  if (isValidVariableName(str)) return str;
+
+  str = str.replace(/\r/g, '');
+  let hash = 5381;
+  let i = str.length;
+
+  while (i--) hash = ((hash << 5) - hash) ^ str.charCodeAt(i);
+  return `template_${(hash >>> 0).toString(36)}`;
+}