core-components: use built-in async react-syntax-highlighter component

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

.changeset/brave-spoons-grow.md

@@ -0,0 +1,5 @@
+---
+'@backstage/core-components': patch
+---
+
+Switched to relying on the built-in support for async loading in `react-syntax-highlighter`. This should provide further improvements to async rendering and lazy loading, and avoid test flakiness that was happening because of the significant number or resources being loaded in lazily all at once.

packages/core-components/src/components/CodeSnippet/CodeSnippet.test.tsx

@@ -31,6 +31,12 @@ const minProps = {
 };
 
 describe('<CodeSnippet />', () => {
+  // react-syntax-highlighter is large and can cause significant slowdowns
+  // This test makes sure we're loading things in asynchronously and not too broadly.
+  it('renders quickly', async () => {
+    await renderInTestApp(<CodeSnippet text="" language="javascript" />);
+  }, 1000);
+
   it('renders text without exploding', async () => {
     const { getByText } = await renderInTestApp(<CodeSnippet {...minProps} />);
     expect(getByText(/"Hello"/)).toBeInTheDocument();

packages/core-components/src/components/CodeSnippet/CodeSnippet.tsx

@@ -14,56 +14,13 @@
  * limitations under the License.
  */
 
-import React, { lazy, Suspense } from 'react';
+import React from 'react';
 import { useTheme } from '@material-ui/core/styles';
 import { BackstageTheme } from '@backstage/theme';
 import { CopyTextButton } from '../CopyTextButton';
-import { Progress } from '../Progress';
-
-const LazySyntaxHighlighter = lazy(async () => {
-  const [{ default: SyntaxHighlighter }, { docco, dark }] = await Promise.all([
-    import('react-syntax-highlighter'),
-    import('react-syntax-highlighter/dist/cjs/styles/hljs'),
-  ]);
-
-  function LazyHighlighter(props: CodeSnippetProps) {
-    const {
-      text,
-      language,
-      showLineNumbers = false,
-      highlightedNumbers,
-      customStyle,
-    } = props;
-    const theme = useTheme<BackstageTheme>();
-    const mode = theme.palette.type === 'dark' ? dark : docco;
-    const highlightColor =
-      theme.palette.type === 'dark' ? '#256bf3' : '#e6ffed';
-
-    return (
-      <SyntaxHighlighter
-        customStyle={customStyle}
-        language={language}
-        style={mode}
-        showLineNumbers={showLineNumbers}
-        wrapLines
-        lineNumberStyle={{ color: theme.palette.textVerySubtle }}
-        lineProps={(lineNumber: number) =>
-          highlightedNumbers?.includes(lineNumber)
-            ? {
-                style: {
-                  backgroundColor: highlightColor,
-                },
-              }
-            : {}
-        }
-      >
-        {text}
-      </SyntaxHighlighter>
-    );
-  }
-
-  return { default: LazyHighlighter };
-});
+import { LightAsync } from 'react-syntax-highlighter';
+import dark from 'react-syntax-highlighter/dist/esm/styles/hljs/dark';
+import docco from 'react-syntax-highlighter/dist/esm/styles/hljs/docco';
 
 /**
  * Properties for {@link CodeSnippet}
@@ -112,12 +69,39 @@ export interface CodeSnippetProps {
  * providing consistent theming and copy code button
  */
 export function CodeSnippet(props: CodeSnippetProps) {
-  const { text, showCopyCodeButton = false } = props;
+  const {
+    text,
+    language,
+    showLineNumbers = false,
+    highlightedNumbers,
+    customStyle,
+    showCopyCodeButton = false,
+  } = props;
+  const theme = useTheme<BackstageTheme>();
+  const mode = theme.palette.type === 'dark' ? dark : docco;
+  const highlightColor = theme.palette.type === 'dark' ? '#256bf3' : '#e6ffed';
+
   return (
     <div style={{ position: 'relative' }}>
-      <Suspense fallback={<Progress />}>
-        <LazySyntaxHighlighter {...props} />
-      </Suspense>
+      <LightAsync
+        customStyle={customStyle}
+        language={language}
+        style={mode}
+        showLineNumbers={showLineNumbers}
+        wrapLines
+        lineNumberStyle={{ color: theme.palette.textVerySubtle }}
+        lineProps={(lineNumber: number) =>
+          highlightedNumbers?.includes(lineNumber)
+            ? {
+                style: {
+                  backgroundColor: highlightColor,
+                },
+              }
+            : {}
+        }
+      >
+        {text}
+      </LightAsync>
       {showCopyCodeButton && (
         <div style={{ position: 'absolute', top: 0, right: 0 }}>
           <CopyTextButton text={text} />