prevent new language adapter instances being created on keypress (#6459)

## 📝 Summary

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If this PR fixes any issues, list them here by number (e.g., Fixes
#123).
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Previously new adapters were created on every keystroke, this only
triggers the initialization once. We have to use getters for circular
deps issues.

## 🔍 Description of Changes

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problem addressed and how it was resolved. If applicable, provide before
and after comparisons, screenshots, or any relevant details to help
reviewers understand the changes easily.
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## 📋 Checklist

- [x] I have read the [contributor
guidelines](https://github.com/marimo-team/marimo/blob/main/CONTRIBUTING.md).
- [ ] For large changes, or changes that affect the public API: this
change was discussed or approved through an issue, on
[Discord](https://marimo.io/discord?ref=pr), or the community
[discussions](https://github.com/marimo-team/marimo/discussions) (Please
provide a link if applicable).
- [ ] I have added tests for the changes made.
- [x] I have run the code and verified that it works as expected.

Author: Light2Dark

frontend/src/components/editor/cell/CreateCellButton.tsx

@@ -9,8 +9,7 @@ import {
 } from "@/components/ui/context-menu";
 import { maybeAddMarimoImport } from "@/core/cells/add-missing-import";
 import { useCellActions } from "@/core/cells/cells";
-import { MarkdownLanguageAdapter } from "@/core/codemirror/language/languages/markdown";
-import { SQLLanguageAdapter } from "@/core/codemirror/language/languages/sql/sql";
+import { LanguageAdapters } from "@/core/codemirror/language/LanguageAdapters";
 import {
   getConnectionTooltip,
   isAppInteractionDisabled,
@@ -103,7 +102,7 @@ const CreateCellButtonContextMenu = (props: {
             evt.stopPropagation();
             maybeAddMarimoImport({ autoInstantiate: true, createNewCell });
             onClick({
-              code: new MarkdownLanguageAdapter().defaultCode,
+              code: LanguageAdapters.markdown.defaultCode,
               hideCode: true,
             });
           }}
@@ -118,7 +117,7 @@ const CreateCellButtonContextMenu = (props: {
           onSelect={(evt) => {
             evt.stopPropagation();
             maybeAddMarimoImport({ autoInstantiate: true, createNewCell });
-            onClick({ code: new SQLLanguageAdapter().defaultCode });
+            onClick({ code: LanguageAdapters.sql.defaultCode });
           }}
         >
           <div className="mr-3 text-muted-foreground">

frontend/src/components/editor/cell/code/language-toggle.tsx

@@ -7,8 +7,7 @@ import { useMemo } from "react";
 import { Button } from "@/components/ui/button";
 import { Tooltip } from "@/components/ui/tooltip";
 import { switchLanguage } from "@/core/codemirror/language/extension";
-import { MarkdownLanguageAdapter } from "@/core/codemirror/language/languages/markdown";
-import { SQLLanguageAdapter } from "@/core/codemirror/language/languages/sql/sql";
+import { LanguageAdapters } from "@/core/codemirror/language/LanguageAdapters";
 import type { LanguageAdapter } from "@/core/codemirror/language/types";
 import { Functions } from "@/utils/functions";
 import { MarkdownIcon, PythonIcon } from "./icons";
@@ -27,11 +26,11 @@ export const LanguageToggles: React.FC<LanguageTogglesProps> = ({
   onAfterToggle,
 }) => {
   const canUseMarkdown = useMemo(
-    () => new MarkdownLanguageAdapter().isSupported(code) || code.trim() === "",
+    () => LanguageAdapters.markdown.isSupported(code) || code.trim() === "",
     [code],
   );
   const canUseSQL = useMemo(
-    () => new SQLLanguageAdapter().isSupported(code) || code.trim() === "",
+    () => LanguageAdapters.sql.isSupported(code) || code.trim() === "",
     [code],
   );
 

frontend/src/components/editor/renderers/CellArray.tsx

@@ -20,8 +20,7 @@ import { SortableCellsProvider } from "@/components/sort/SortableCellsProvider";
 import { Button } from "@/components/ui/button";
 import { Tooltip } from "@/components/ui/tooltip";
 import { maybeAddMarimoImport } from "@/core/cells/add-missing-import";
-import { MarkdownLanguageAdapter } from "@/core/codemirror/language/languages/markdown";
-import { SQLLanguageAdapter } from "@/core/codemirror/language/languages/sql/sql";
+import { LanguageAdapters } from "@/core/codemirror/language/LanguageAdapters";
 import { aiEnabledAtom } from "@/core/config/config";
 import { isConnectedAtom } from "@/core/network/connection";
 import { useBoolean } from "@/hooks/useBoolean";
@@ -288,7 +287,7 @@ const AddCellButtons: React.FC<{
             createNewCell({
               cellId: { type: "__end__", columnId },
               before: false,
-              code: new MarkdownLanguageAdapter().defaultCode,
+              code: LanguageAdapters.markdown.defaultCode,
               hideCode: true,
             });
           }}
@@ -307,7 +306,7 @@ const AddCellButtons: React.FC<{
             createNewCell({
               cellId: { type: "__end__", columnId },
               before: false,
-              code: new SQLLanguageAdapter().defaultCode,
+              code: LanguageAdapters.sql.defaultCode,
             });
           }}
         >

frontend/src/core/codemirror/language/LanguageAdapters.ts

@@ -1,20 +1,26 @@
 /* Copyright 2024 Marimo. All rights reserved. */
 
+import { once } from "@/utils/once";
 import { MarkdownLanguageAdapter } from "./languages/markdown";
 import { PythonLanguageAdapter } from "./languages/python";
 import { SQLLanguageAdapter } from "./languages/sql/sql";
 import type { LanguageAdapter, LanguageAdapterType } from "./types";
 
+// Create cached instances
+const createPythonAdapter = once(() => new PythonLanguageAdapter());
+const createMarkdownAdapter = once(() => new MarkdownLanguageAdapter());
+const createSqlAdapter = once(() => new SQLLanguageAdapter());
+
 export const LanguageAdapters: Record<LanguageAdapterType, LanguageAdapter> = {
   // Getters to prevent circular dependencies
   get python() {
-    return new PythonLanguageAdapter();
+    return createPythonAdapter();
   },
   get markdown() {
-    return new MarkdownLanguageAdapter();
+    return createMarkdownAdapter();
   },
   get sql() {
-    return new SQLLanguageAdapter();
+    return createSqlAdapter();
   },
 };