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a6b58a8b2f
* perf: improve performance of `experimentalSourceRewriting` This change is in addition to https://github.com/benjamn/recast/pull/1399. This commit focuses on Cypress' use of recast, with the following optimizations: 1. Avoid printing the source file again if no change was made. Printing an AST using recast does reuse the original text, but identifying for which parts of the AST reuse is possible comes with noticeable overhead. By tracking changes within the visitor it becomes possible to skip this phase entirely if no changes were made. 2. Avoid a scope lookup (`path.scope.declares(node.name)`) for all identifiers in the program, doing it only for identifiers that may have to be rewritten. With these changes, a 2.6MB bundle that does not need rewriting has improved from 4.4s to 2.3s, provided that the above-mentioned recast PR has been applied. * chore: move `experimentalSourceRewriting` release note to pending release section --------- Co-authored-by: Bill Glesias <bglesias@gmail.com> Co-authored-by: Jennifer Shehane <jennifer@cypress.io>
108 lines
3.0 KiB
TypeScript
108 lines
3.0 KiB
TypeScript
import * as astTypes from 'ast-types'
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import Debug from 'debug'
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import { jsRules } from './js-rules'
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import * as recast from 'recast'
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import * as sourceMaps from './util/source-maps'
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const debug = Debug('cypress:rewriter:js')
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const defaultPrintOpts: recast.Options = {
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// will only affect reprinted quotes
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quote: 'single',
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}
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type OriginalSourceInfo = { url: string, js: string }
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function _generateDriverError (url: string, err: Error) {
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const args = JSON.stringify({
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errMessage: err.message,
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errStack: err.stack,
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url,
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})
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return `window.top.Cypress.utils.throwErrByPath('proxy.js_rewriting_failed', { args: ${args} })`
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}
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// a function that, given source info, returns an id that can be used to build the sourcemap later
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export type DeferSourceMapRewriteFn = (sourceInfo: OriginalSourceInfo) => string
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export function rewriteJsSourceMap (url: string, js: string, inputSourceMap: any): any {
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try {
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const { sourceFileName, sourceMapName, sourceRoot } = sourceMaps.getPaths(url)
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const ast = recast.parse(js, { sourceFileName })
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const visitor = astTypes.PathVisitor.fromMethodsObject(jsRules)
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visitor.visit(ast)
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if (!visitor.wasChangeReported() && inputSourceMap) {
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return inputSourceMap
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}
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return recast.print(ast, {
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inputSourceMap,
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sourceMapName,
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sourceRoot,
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...defaultPrintOpts,
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}).map
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} catch (err) {
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debug('error while parsing JS %o', { err, js: js.slice ? js.slice(0, 500) : js })
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return { err }
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}
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}
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export function _rewriteJsUnsafe (url: string, js: string, deferSourceMapRewrite?: DeferSourceMapRewriteFn): string {
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const ast = recast.parse(js)
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let didRewrite: boolean
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try {
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const visitor = astTypes.PathVisitor.fromMethodsObject(jsRules)
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visitor.visit(ast)
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didRewrite = visitor.wasChangeReported()
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} catch (err: any) {
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// if visiting fails, it points to a bug in our rewriting logic, so raise the error to the driver
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return _generateDriverError(url, err)
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}
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let rewritten: string
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if (didRewrite) {
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const { code } = recast.print(ast, defaultPrintOpts)
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rewritten = code
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} else {
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rewritten = js
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}
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if (!deferSourceMapRewrite) {
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// no sourcemaps
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return sourceMaps.stripMappingUrl(rewritten)
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}
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// get an ID that can be used to lazy-generate the source map later
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const sourceMapId = deferSourceMapRewrite({ url, js })
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return sourceMaps.urlFormatter(
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// using a relative URL ensures that required cookies + other headers are sent along
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// and can be reused if the user's sourcemap requires an HTTP request to be made
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`/__cypress/source-maps/${sourceMapId}.map`,
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rewritten,
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)
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}
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export function rewriteJs (url: string, js: string, deferSourceMapRewrite?: DeferSourceMapRewriteFn): string {
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try {
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// rewriting can throw on invalid JS or if there are bugs in the js-rules, so always wrap it
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return _rewriteJsUnsafe(url, js, deferSourceMapRewrite)
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} catch (err) {
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debug('error while parsing JS %o', { err, js: js.slice ? js.slice(0, 500) : js })
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return js
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}
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}
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