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refactor the JSX plugin to improve performance (#4405)
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@FredKSchott
FredKSchott authored Aug 22, 2022
1 parent dd52b21 commit a70f69a
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5 changes: 5 additions & 0 deletions .changeset/silver-dragons-run.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
'astro': patch
---

Refactor JSX build plugin, improve performance
222 changes: 112 additions & 110 deletions packages/astro/src/vite-plugin-jsx/index.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,6 @@ import { error } from '../core/logger/core.js';
import { parseNpmName } from '../core/util.js';
import tagExportsPlugin from './tag.js';

const JSX_RENDERER_CACHE = new WeakMap<AstroConfig, Map<string, AstroRenderer>>();
const JSX_EXTENSIONS = new Set(['.jsx', '.tsx', '.mdx']);
const IMPORT_STATEMENTS: Record<string, string> = {
react: "import React from 'react'",
Expand All @@ -26,6 +25,8 @@ const IMPORT_STATEMENTS: Record<string, string> = {
// The `tsx` loader in esbuild will remove unused imports, so we need to
// be careful about esbuild not treating h, React, Fragment, etc. as unused.
const PREVENT_UNUSED_IMPORTS = ';;(React,Fragment,h);';
// A fast check regex for the import keyword. False positives are okay.
const IMPORT_KEYWORD_REGEX = /import/;

function getEsbuildLoader(fileExt: string): string {
if (fileExt === '.mdx') return 'jsx';
Expand All @@ -39,6 +40,53 @@ function collectJSXRenderers(renderers: AstroRenderer[]): Map<string, AstroRende
);
}

/**
* Scan a file for an explicit @jsxImportSource comment.
* If one is found, return it's value. Otherwise, return undefined.
*/
function detectImportSourceFromComments(code: string): string | undefined {
// if no imports were found, look for @jsxImportSource comment
const multiline = code.match(/\/\*\*?[\S\s]*\*\//gm) || [];
for (const comment of multiline) {
const [_, lib] = comment.slice(0, -2).match(/@jsxImportSource\s*(\S+)/) || [];
if (lib) {
return lib.trim();
}
}
}

/**
* Scan a file's imports to detect which renderer it may need.
* ex: if the file imports "preact", it's safe to assume the
* component should be built as a Preact component.
* If no relevant imports found, return undefined.
*/
async function detectImportSourceFromImports(
code: string,
id: string,
jsxRenderers: Map<string, AstroRenderer>
) {
// We need valid JS to scan for imports.
// NOTE: Because we only need imports, it is okay to use `h` and `Fragment` as placeholders.
const { code: jsCode } = await esbuild.transform(code + PREVENT_UNUSED_IMPORTS, {
loader: getEsbuildLoader(path.extname(id)) as esbuild.Loader,
jsx: 'transform',
jsxFactory: 'h',
jsxFragment: 'Fragment',
sourcefile: id,
sourcemap: 'inline',
});
const [imports] = eslexer.parse(jsCode);
if (imports.length > 0) {
for (let { n: spec } of imports) {
const pkg = spec && parseNpmName(spec);
if (!pkg) continue;
if (jsxRenderers.has(pkg.name)) {
return pkg.name;
}
}
}
}
interface TransformJSXOptions {
code: string;
id: string;
Expand Down Expand Up @@ -106,12 +154,29 @@ interface AstroPluginJSXOptions {
/** Use Astro config to allow for alternate or multiple JSX renderers (by default Vite will assume React) */
export default function jsx({ config, logging }: AstroPluginJSXOptions): Plugin {
let viteConfig: ResolvedConfig;
const jsxRenderers = new Map<string, AstroRenderer>();
const jsxRenderersIntegrationOnly = new Map<string, AstroRenderer>();
// A reference to Astro's internal JSX renderer.
let astroJSXRenderer: AstroRenderer;
// The first JSX renderer provided is considered the default renderer.
// This is a useful reference for when the user only gives a single render.
let defaultJSXRendererEntry: [string, AstroRenderer];

return {
name: 'astro:jsx',
enforce: 'pre', // run transforms before other plugins
configResolved(resolvedConfig) {
async configResolved(resolvedConfig) {
viteConfig = resolvedConfig;
const possibleRenderers = await collectJSXRenderers(config._ctx.renderers);
for (const [importSource, renderer] of possibleRenderers) {
jsxRenderers.set(importSource, renderer);
if (importSource === 'astro') {
astroJSXRenderer = renderer;
} else {
jsxRenderersIntegrationOnly.set(importSource, renderer);
}
}
defaultJSXRendererEntry = [...jsxRenderersIntegrationOnly.entries()][0];
},
async transform(code, id, opts) {
const ssr = Boolean(opts?.ssr);
Expand All @@ -120,30 +185,8 @@ export default function jsx({ config, logging }: AstroPluginJSXOptions): Plugin
}

const { mode } = viteConfig;
let jsxRenderers = JSX_RENDERER_CACHE.get(config);

// load renderers (on first run only)
if (!jsxRenderers) {
jsxRenderers = new Map();
const possibleRenderers = await collectJSXRenderers(config._ctx.renderers);
if (possibleRenderers.size === 0) {
// note: we have filtered out all non-JSX files, so this error should only show if a JSX file is loaded with no matching renderers
throw new Error(
`${colors.yellow(
id
)}\nUnable to resolve a JSX renderer! Did you forget to include one? Add a JSX integration like \`@astrojs/react\` to your \`astro.config.mjs\` file.`
);
}
for (const [importSource, renderer] of possibleRenderers) {
jsxRenderers.set(importSource, renderer);
}
JSX_RENDERER_CACHE.set(config, jsxRenderers);
}

const astroRenderer = jsxRenderers.get('astro');

// Shortcut: only use Astro renderer for MD and MDX files
if ((id.includes('.mdx') || id.includes('.md')) && astroRenderer) {
if (id.includes('.mdx') || id.includes('.md')) {
const { code: jsxCode } = await esbuild.transform(code, {
loader: getEsbuildLoader(path.extname(id)) as esbuild.Loader,
jsx: 'preserve',
Expand All @@ -153,18 +196,12 @@ export default function jsx({ config, logging }: AstroPluginJSXOptions): Plugin
return transformJSX({
code: jsxCode,
id,
renderer: astroRenderer,
renderer: astroJSXRenderer,
mode,
ssr,
});
}

// Attempt: Single JSX integration
// If we only have one renderer, we can skip a bunch of work!
const nonAstroJsxRenderers = new Map(
[...jsxRenderers.entries()].filter(([key]) => key !== 'astro')
);
if (nonAstroJsxRenderers.size === 1) {
if (defaultJSXRendererEntry && jsxRenderersIntegrationOnly.size === 1) {
// downlevel any non-standard syntax, but preserve JSX
const { code: jsxCode } = await esbuild.transform(code, {
loader: getEsbuildLoader(path.extname(id)) as esbuild.Loader,
Expand All @@ -175,95 +212,60 @@ export default function jsx({ config, logging }: AstroPluginJSXOptions): Plugin
return transformJSX({
code: jsxCode,
id,
renderer: [...nonAstroJsxRenderers.values()][0],
renderer: defaultJSXRendererEntry[1],
mode,
ssr,
});
}

// Attempt: Multiple JSX renderers
// we need valid JS to scan, so we can use `h` and `Fragment` as placeholders
const { code: jsCode } = await esbuild.transform(code + PREVENT_UNUSED_IMPORTS, {
loader: getEsbuildLoader(path.extname(id)) as esbuild.Loader,
jsx: 'transform',
jsxFactory: 'h',
jsxFragment: 'Fragment',
sourcefile: id,
sourcemap: 'inline',
});

let imports: eslexer.ImportSpecifier[] = [];
if (/import/.test(jsCode)) {
let [i] = eslexer.parse(jsCode);
imports = i as any;
}
let importSource: string | undefined;
if (imports.length > 0) {
for (let { n: spec } of imports) {
const pkg = spec && parseNpmName(spec);
if (!pkg) continue;
if (jsxRenderers.has(pkg.name)) {
importSource = pkg.name;
break;
}
}
let importSource = detectImportSourceFromComments(code);
if (!importSource && IMPORT_KEYWORD_REGEX.test(code)) {
importSource = await detectImportSourceFromImports(code, id, jsxRenderers);
}

// if no imports were found, look for @jsxImportSource comment
// if we still can’t tell the import source, now is the time to throw an error.
if (!importSource) {
const multiline = code.match(/\/\*\*?[\S\s]*\*\//gm) || [];
for (const comment of multiline) {
const [_, lib] = comment.slice(0, -2).match(/@jsxImportSource\s*(\S+)/) || [];
if (lib) {
importSource = lib.trim();
break;
}
}
const [defaultRendererName] = defaultJSXRendererEntry[0];
error(
logging,
'renderer',
`${colors.yellow(id)}
Unable to resolve a renderer that handles this file! With more than one renderer enabled, you should include an import or use a pragma comment.
Add ${colors.cyan(
IMPORT_STATEMENTS[defaultRendererName] || `import '${defaultRendererName}';`
)} or ${colors.cyan(`/* jsxImportSource: ${defaultRendererName} */`)} to this file.
`
);
return null;
}

// if JSX renderer found, then use that
if (importSource) {
const jsxRenderer = jsxRenderers.get(importSource);
// if renderer not installed for this JSX source, throw error
if (!jsxRenderer) {
error(
logging,
'renderer',
`${colors.yellow(
id
)} No renderer installed for ${importSource}. Try adding \`@astrojs/${importSource}\` to your project.`
);
return null;
}
// downlevel any non-standard syntax, but preserve JSX
const { code: jsxCode } = await esbuild.transform(code, {
loader: getEsbuildLoader(path.extname(id)) as esbuild.Loader,
jsx: 'preserve',
sourcefile: id,
sourcemap: 'inline',
});
return await transformJSX({
code: jsxCode,
id,
renderer: jsxRenderers.get(importSource) as AstroRenderer,
mode,
ssr,
});
const selectedJsxRenderer = jsxRenderers.get(importSource);
// if the renderer is not installed for this JSX source, throw error
if (!selectedJsxRenderer) {
error(
logging,
'renderer',
`${colors.yellow(
id
)} No renderer installed for ${importSource}. Try adding \`@astrojs/${importSource}\` to your project.`
);
return null;
}

// if we still can’t tell, throw error
const defaultRenderer = [...jsxRenderers.keys()][0];
error(
logging,
'renderer',
`${colors.yellow(id)}
Unable to resolve a renderer that handles this file! With more than one renderer enabled, you should include an import or use a pragma comment.
Add ${colors.cyan(
IMPORT_STATEMENTS[defaultRenderer] || `import '${defaultRenderer}';`
)} or ${colors.cyan(`/* jsxImportSource: ${defaultRenderer} */`)} to this file.
`
);
return null;
// downlevel any non-standard syntax, but preserve JSX
const { code: jsxCode } = await esbuild.transform(code, {
loader: getEsbuildLoader(path.extname(id)) as esbuild.Loader,
jsx: 'preserve',
sourcefile: id,
sourcemap: 'inline',
});
return await transformJSX({
code: jsxCode,
id,
renderer: selectedJsxRenderer,
mode,
ssr,
});
},
};
}

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