Appearance
生成代码
generate
- 在 AST 转换后 会执行 generate 函数生成代码
- generate 函数的输入 就是转换后的 AST 节点
- 主要做了五件事情
- 创建代码生成上下文
- 生成预设代码
- 生成渲染函数的名称和参数
- 生成资源声明代码
- 生成创建 vnode 树的表达式
js
export function generate(
ast: RootNode,
options: CodegenOptions & {
onContextCreated?: (context: CodegenContext) => void
} = {}
): CodegenResult {
const context = createCodegenContext(ast, options)
if (options.onContextCreated) options.onContextCreated(context)
const {
mode,
push,
prefixIdentifiers,
indent,
deindent,
newline,
scopeId,
ssr
} = context
const hasHelpers = ast.helpers.length > 0
const useWithBlock = !prefixIdentifiers && mode !== 'module'
const genScopeId = !__BROWSER__ && scopeId != null && mode === 'module'
const isSetupInlined = !__BROWSER__ && !!options.inline
// preambles
// in setup() inline mode, the preamble is generated in a sub context
// and returned separately.
const preambleContext = isSetupInlined
? createCodegenContext(ast, options)
: context
if (!__BROWSER__ && mode === 'module') {
genModulePreamble(ast, preambleContext, genScopeId, isSetupInlined)
} else {
genFunctionPreamble(ast, preambleContext)
}
// enter render function
const functionName = ssr ? `ssrRender` : `render`
const args = ssr ? ['_ctx', '_push', '_parent', '_attrs'] : ['_ctx', '_cache']
if (!__BROWSER__ && options.bindingMetadata && !options.inline) {
// binding optimization args
args.push('$props', '$setup', '$data', '$options')
}
const signature =
!__BROWSER__ && options.isTS
? args.map(arg => `${arg}: any`).join(',')
: args.join(', ')
if (isSetupInlined) {
push(`(${signature}) => {`)
} else {
push(`function ${functionName}(${signature}) {`)
}
indent()
if (useWithBlock) {
push(`with (_ctx) {`)
indent()
// function mode const declarations should be inside with block
// also they should be renamed to avoid collision with user properties
if (hasHelpers) {
push(`const { ${ast.helpers.map(aliasHelper).join(', ')} } = _Vue`)
push(`\n`)
newline()
}
}
// generate asset resolution statements
if (ast.components.length) {
genAssets(ast.components, 'component', context)
if (ast.directives.length || ast.temps > 0) {
newline()
}
}
if (ast.directives.length) {
genAssets(ast.directives, 'directive', context)
if (ast.temps > 0) {
newline()
}
}
if (__COMPAT__ && ast.filters && ast.filters.length) {
newline()
genAssets(ast.filters, 'filter', context)
newline()
}
if (ast.temps > 0) {
push(`let `)
for (let i = 0; i < ast.temps; i++) {
push(`${i > 0 ? `, ` : ``}_temp${i}`)
}
}
if (ast.components.length || ast.directives.length || ast.temps) {
push(`\n`)
newline()
}
// generate the VNode tree expression
if (!ssr) {
push(`return `)
}
if (ast.codegenNode) {
genNode(ast.codegenNode, context)
} else {
push(`null`)
}
if (useWithBlock) {
deindent()
push(`}`)
}
deindent()
push(`}`)
return {
ast,
code: context.code,
preamble: isSetupInlined ? preambleContext.code : ``,
// SourceMapGenerator does have toJSON() method but it's not in the types
map: context.map ? (context.map as any).toJSON() : undefined
}
}