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ssrTransform.ts
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ssrTransform.ts
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import MagicString from 'magic-string'
import type { SourceMap } from 'rollup'
import type {
Function as FunctionNode,
Identifier,
Pattern,
Property,
VariableDeclaration,
Node as _Node,
} from 'estree'
import { extract_names as extractNames } from 'periscopic'
import { walk as eswalk } from 'estree-walker'
import type { RawSourceMap } from '@ampproject/remapping'
import type { TransformResult } from '../server/transformRequest'
import { parser } from '../server/pluginContainer'
import { combineSourcemaps } from '../utils'
import { isJSONRequest } from '../plugins/json'
type Node = _Node & {
start: number
end: number
}
interface TransformOptions {
json?: {
stringify?: boolean
}
}
export const ssrModuleExportsKey = `__vite_ssr_exports__`
export const ssrImportKey = `__vite_ssr_import__`
export const ssrDynamicImportKey = `__vite_ssr_dynamic_import__`
export const ssrExportAllKey = `__vite_ssr_exportAll__`
export const ssrImportMetaKey = `__vite_ssr_import_meta__`
const hashbangRE = /^#!.*\n/
export async function ssrTransform(
code: string,
inMap: SourceMap | null,
url: string,
originalCode: string,
options?: TransformOptions,
): Promise<TransformResult | null> {
if (options?.json?.stringify && isJSONRequest(url)) {
return ssrTransformJSON(code, inMap)
}
return ssrTransformScript(code, inMap, url, originalCode)
}
async function ssrTransformJSON(
code: string,
inMap: SourceMap | null,
): Promise<TransformResult> {
return {
code: code.replace('export default', `${ssrModuleExportsKey}.default =`),
map: inMap,
deps: [],
dynamicDeps: [],
}
}
async function ssrTransformScript(
code: string,
inMap: SourceMap | null,
url: string,
originalCode: string,
): Promise<TransformResult | null> {
const s = new MagicString(code)
let ast: any
try {
ast = parser.parse(code, {
sourceType: 'module',
ecmaVersion: 'latest',
locations: true,
allowHashBang: true,
})
} catch (err) {
if (!err.loc || !err.loc.line) throw err
const line = err.loc.line
throw new Error(
`Parse failure: ${
err.message
}\nAt file: ${url}\nContents of line ${line}: ${
code.split('\n')[line - 1]
}`,
)
}
let uid = 0
const deps = new Set<string>()
const dynamicDeps = new Set<string>()
const idToImportMap = new Map<string, string>()
const declaredConst = new Set<string>()
// hoist at the start of the file, after the hashbang
const hoistIndex = code.match(hashbangRE)?.[0].length ?? 0
function defineImport(source: string) {
deps.add(source)
const importId = `__vite_ssr_import_${uid++}__`
// There will be an error if the module is called before it is imported,
// so the module import statement is hoisted to the top
s.appendLeft(
hoistIndex,
`const ${importId} = await ${ssrImportKey}(${JSON.stringify(source)});\n`,
)
return importId
}
function defineExport(position: number, name: string, local = name) {
s.appendLeft(
position,
`\nObject.defineProperty(${ssrModuleExportsKey}, "${name}", ` +
`{ enumerable: true, configurable: true, get(){ return ${local} }});`,
)
}
// 1. check all import statements and record id -> importName map
for (const node of ast.body as Node[]) {
// import foo from 'foo' --> foo -> __import_foo__.default
// import { baz } from 'foo' --> baz -> __import_foo__.baz
// import * as ok from 'foo' --> ok -> __import_foo__
if (node.type === 'ImportDeclaration') {
const importId = defineImport(node.source.value as string)
s.remove(node.start, node.end)
for (const spec of node.specifiers) {
if (spec.type === 'ImportSpecifier') {
idToImportMap.set(
spec.local.name,
`${importId}.${spec.imported.name}`,
)
} else if (spec.type === 'ImportDefaultSpecifier') {
idToImportMap.set(spec.local.name, `${importId}.default`)
} else {
// namespace specifier
idToImportMap.set(spec.local.name, importId)
}
}
}
}
// 2. check all export statements and define exports
for (const node of ast.body as Node[]) {
// named exports
if (node.type === 'ExportNamedDeclaration') {
if (node.declaration) {
if (
node.declaration.type === 'FunctionDeclaration' ||
node.declaration.type === 'ClassDeclaration'
) {
// export function foo() {}
defineExport(node.end, node.declaration.id!.name)
} else {
// export const foo = 1, bar = 2
for (const declaration of node.declaration.declarations) {
const names = extractNames(declaration.id as any)
for (const name of names) {
defineExport(node.end, name)
}
}
}
s.remove(node.start, (node.declaration as Node).start)
} else {
s.remove(node.start, node.end)
if (node.source) {
// export { foo, bar } from './foo'
const importId = defineImport(node.source.value as string)
// hoist re-exports near the defined import so they are immediately exported
for (const spec of node.specifiers) {
defineExport(
hoistIndex,
spec.exported.name,
`${importId}.${spec.local.name}`,
)
}
} else {
// export { foo, bar }
for (const spec of node.specifiers) {
const local = spec.local.name
const binding = idToImportMap.get(local)
defineExport(node.end, spec.exported.name, binding || local)
}
}
}
}
// default export
if (node.type === 'ExportDefaultDeclaration') {
const expressionTypes = ['FunctionExpression', 'ClassExpression']
if (
'id' in node.declaration &&
node.declaration.id &&
!expressionTypes.includes(node.declaration.type)
) {
// named hoistable/class exports
// export default function foo() {}
// export default class A {}
const { name } = node.declaration.id
s.remove(node.start, node.start + 15 /* 'export default '.length */)
s.append(
`\nObject.defineProperty(${ssrModuleExportsKey}, "default", ` +
`{ enumerable: true, configurable: true, value: ${name} });`,
)
} else {
// anonymous default exports
s.update(
node.start,
node.start + 14 /* 'export default'.length */,
`${ssrModuleExportsKey}.default =`,
)
}
}
// export * from './foo'
if (node.type === 'ExportAllDeclaration') {
s.remove(node.start, node.end)
const importId = defineImport(node.source.value as string)
// hoist re-exports near the defined import so they are immediately exported
if (node.exported) {
defineExport(hoistIndex, node.exported.name, `${importId}`)
} else {
s.appendLeft(hoistIndex, `${ssrExportAllKey}(${importId});\n`)
}
}
}
// 3. convert references to import bindings & import.meta references
walk(ast, {
onIdentifier(id, parent, parentStack) {
const grandparent = parentStack[1]
const binding = idToImportMap.get(id.name)
if (!binding) {
return
}
if (isStaticProperty(parent) && parent.shorthand) {
// let binding used in a property shorthand
// { foo } -> { foo: __import_x__.foo }
// skip for destructuring patterns
if (
!isNodeInPattern(parent) ||
isInDestructuringAssignment(parent, parentStack)
) {
s.appendLeft(id.end, `: ${binding}`)
}
} else if (
(parent.type === 'PropertyDefinition' &&
grandparent?.type === 'ClassBody') ||
(parent.type === 'ClassDeclaration' && id === parent.superClass)
) {
if (!declaredConst.has(id.name)) {
declaredConst.add(id.name)
// locate the top-most node containing the class declaration
const topNode = parentStack[parentStack.length - 2]
s.prependRight(topNode.start, `const ${id.name} = ${binding};\n`)
}
} else {
s.update(id.start, id.end, binding)
}
},
onImportMeta(node) {
s.update(node.start, node.end, ssrImportMetaKey)
},
onDynamicImport(node) {
s.update(node.start, node.start + 6, ssrDynamicImportKey)
if (node.type === 'ImportExpression' && node.source.type === 'Literal') {
dynamicDeps.add(node.source.value as string)
}
},
})
let map = s.generateMap({ hires: true })
if (inMap && inMap.mappings && inMap.sources.length > 0) {
map = combineSourcemaps(
url,
[
{
...map,
sources: inMap.sources,
sourcesContent: inMap.sourcesContent,
} as RawSourceMap,
inMap as RawSourceMap,
],
false,
) as SourceMap
} else {
map.sources = [url]
// needs to use originalCode instead of code
// because code might be already transformed even if map is null
map.sourcesContent = [originalCode]
}
return {
code: s.toString(),
map,
deps: [...deps],
dynamicDeps: [...dynamicDeps],
}
}
interface Visitors {
onIdentifier: (
node: Identifier & {
start: number
end: number
},
parent: Node,
parentStack: Node[],
) => void
onImportMeta: (node: Node) => void
onDynamicImport: (node: Node) => void
}
const isNodeInPatternWeakSet = new WeakSet<_Node>()
const setIsNodeInPattern = (node: Property) => isNodeInPatternWeakSet.add(node)
const isNodeInPattern = (node: _Node): node is Property =>
isNodeInPatternWeakSet.has(node)
/**
* Same logic from \@vue/compiler-core & \@vue/compiler-sfc
* Except this is using acorn AST
*/
function walk(
root: Node,
{ onIdentifier, onImportMeta, onDynamicImport }: Visitors,
) {
const parentStack: Node[] = []
const varKindStack: VariableDeclaration['kind'][] = []
const scopeMap = new WeakMap<_Node, Set<string>>()
const identifiers: [id: any, stack: Node[]][] = []
const setScope = (node: _Node, name: string) => {
let scopeIds = scopeMap.get(node)
if (scopeIds && scopeIds.has(name)) {
return
}
if (!scopeIds) {
scopeIds = new Set()
scopeMap.set(node, scopeIds)
}
scopeIds.add(name)
}
function isInScope(name: string, parents: Node[]) {
return parents.some((node) => node && scopeMap.get(node)?.has(name))
}
function handlePattern(p: Pattern, parentScope: _Node) {
if (p.type === 'Identifier') {
setScope(parentScope, p.name)
} else if (p.type === 'RestElement') {
handlePattern(p.argument, parentScope)
} else if (p.type === 'ObjectPattern') {
p.properties.forEach((property) => {
if (property.type === 'RestElement') {
setScope(parentScope, (property.argument as Identifier).name)
} else {
handlePattern(property.value, parentScope)
}
})
} else if (p.type === 'ArrayPattern') {
p.elements.forEach((element) => {
if (element) {
handlePattern(element, parentScope)
}
})
} else if (p.type === 'AssignmentPattern') {
handlePattern(p.left, parentScope)
} else {
setScope(parentScope, (p as any).name)
}
}
;(eswalk as any)(root, {
enter(node: Node, parent: Node | null) {
if (node.type === 'ImportDeclaration') {
return this.skip()
}
// track parent stack, skip for "else-if"/"else" branches as acorn nests
// the ast within "if" nodes instead of flattening them
if (
parent &&
!(parent.type === 'IfStatement' && node === parent.alternate)
) {
parentStack.unshift(parent)
}
// track variable declaration kind stack used by VariableDeclarator
if (node.type === 'VariableDeclaration') {
varKindStack.unshift(node.kind)
}
if (node.type === 'MetaProperty' && node.meta.name === 'import') {
onImportMeta(node)
} else if (node.type === 'ImportExpression') {
onDynamicImport(node)
}
if (node.type === 'Identifier') {
if (
!isInScope(node.name, parentStack) &&
isRefIdentifier(node, parent!, parentStack)
) {
// record the identifier, for DFS -> BFS
identifiers.push([node, parentStack.slice(0)])
}
} else if (isFunction(node)) {
// If it is a function declaration, it could be shadowing an import
// Add its name to the scope so it won't get replaced
if (node.type === 'FunctionDeclaration') {
const parentScope = findParentScope(parentStack)
if (parentScope) {
setScope(parentScope, node.id!.name)
}
}
// walk function expressions and add its arguments to known identifiers
// so that we don't prefix them
node.params.forEach((p) => {
if (p.type === 'ObjectPattern' || p.type === 'ArrayPattern') {
handlePattern(p, node)
return
}
;(eswalk as any)(p.type === 'AssignmentPattern' ? p.left : p, {
enter(child: Node, parent: Node) {
// skip params default value of destructure
if (
parent?.type === 'AssignmentPattern' &&
parent?.right === child
) {
return this.skip()
}
if (child.type !== 'Identifier') return
// do not record as scope variable if is a destructuring keyword
if (isStaticPropertyKey(child, parent)) return
// do not record if this is a default value
// assignment of a destructuring variable
if (
(parent?.type === 'TemplateLiteral' &&
parent?.expressions.includes(child)) ||
(parent?.type === 'CallExpression' && parent?.callee === child)
) {
return
}
setScope(node, child.name)
},
})
})
} else if (node.type === 'Property' && parent!.type === 'ObjectPattern') {
// mark property in destructuring pattern
setIsNodeInPattern(node)
} else if (node.type === 'VariableDeclarator') {
const parentFunction = findParentScope(
parentStack,
varKindStack[0] === 'var',
)
if (parentFunction) {
handlePattern(node.id, parentFunction)
}
} else if (node.type === 'CatchClause' && node.param) {
handlePattern(node.param, node)
}
},
leave(node: Node, parent: Node | null) {
// untrack parent stack from above
if (
parent &&
!(parent.type === 'IfStatement' && node === parent.alternate)
) {
parentStack.shift()
}
if (node.type === 'VariableDeclaration') {
varKindStack.shift()
}
},
})
// emit the identifier events in BFS so the hoisted declarations
// can be captured correctly
identifiers.forEach(([node, stack]) => {
if (!isInScope(node.name, stack)) onIdentifier(node, stack[0], stack)
})
}
function isRefIdentifier(id: Identifier, parent: _Node, parentStack: _Node[]) {
// declaration id
if (
parent.type === 'CatchClause' ||
((parent.type === 'VariableDeclarator' ||
parent.type === 'ClassDeclaration') &&
parent.id === id)
) {
return false
}
if (isFunction(parent)) {
// function declaration/expression id
if ((parent as any).id === id) {
return false
}
// params list
if (parent.params.includes(id)) {
return false
}
}
// class method name
if (parent.type === 'MethodDefinition' && !parent.computed) {
return false
}
// property key
if (isStaticPropertyKey(id, parent)) {
return false
}
// object destructuring pattern
if (isNodeInPattern(parent) && parent.value === id) {
return false
}
// non-assignment array destructuring pattern
if (
parent.type === 'ArrayPattern' &&
!isInDestructuringAssignment(parent, parentStack)
) {
return false
}
// member expression property
if (
parent.type === 'MemberExpression' &&
parent.property === id &&
!parent.computed
) {
return false
}
if (parent.type === 'ExportSpecifier') {
return false
}
// is a special keyword but parsed as identifier
if (id.name === 'arguments') {
return false
}
return true
}
const isStaticProperty = (node: _Node): node is Property =>
node && node.type === 'Property' && !node.computed
const isStaticPropertyKey = (node: _Node, parent: _Node) =>
isStaticProperty(parent) && parent.key === node
const functionNodeTypeRE = /Function(?:Expression|Declaration)$|Method$/
function isFunction(node: _Node): node is FunctionNode {
return functionNodeTypeRE.test(node.type)
}
const blockNodeTypeRE = /^BlockStatement$|^For(?:In|Of)?Statement$/
function isBlock(node: _Node) {
return blockNodeTypeRE.test(node.type)
}
function findParentScope(
parentStack: _Node[],
isVar = false,
): _Node | undefined {
return parentStack.find(isVar ? isFunction : isBlock)
}
function isInDestructuringAssignment(
parent: _Node,
parentStack: _Node[],
): boolean {
if (
parent &&
(parent.type === 'Property' || parent.type === 'ArrayPattern')
) {
return parentStack.some((i) => i.type === 'AssignmentExpression')
}
return false
}