| 406 | } |
| 407 | |
| 408 | function genFunctionPreamble(ast: RootNode, context: CodegenContext) { |
| 409 | const { |
| 410 | ssr, |
| 411 | prefixIdentifiers, |
| 412 | push, |
| 413 | newline, |
| 414 | runtimeModuleName, |
| 415 | runtimeGlobalName, |
| 416 | ssrRuntimeModuleName, |
| 417 | } = context |
| 418 | const VueBinding = |
| 419 | !__BROWSER__ && ssr |
| 420 | ? `require(${JSON.stringify(runtimeModuleName)})` |
| 421 | : runtimeGlobalName |
| 422 | // Generate const declaration for helpers |
| 423 | // In prefix mode, we place the const declaration at top so it's done |
| 424 | // only once; But if we not prefixing, we place the declaration inside the |
| 425 | // with block so it doesn't incur the `in` check cost for every helper access. |
| 426 | const helpers = Array.from(ast.helpers) |
| 427 | if (helpers.length > 0) { |
| 428 | if (!__BROWSER__ && prefixIdentifiers) { |
| 429 | push( |
| 430 | `const { ${helpers.map(aliasHelper).join(', ')} } = ${VueBinding}\n`, |
| 431 | NewlineType.End, |
| 432 | ) |
| 433 | } else { |
| 434 | // "with" mode. |
| 435 | // save Vue in a separate variable to avoid collision |
| 436 | push(`const _Vue = ${VueBinding}\n`, NewlineType.End) |
| 437 | // in "with" mode, helpers are declared inside the with block to avoid |
| 438 | // has check cost, but hoists are lifted out of the function - we need |
| 439 | // to provide the helper here. |
| 440 | if (ast.hoists.length) { |
| 441 | const staticHelpers = [ |
| 442 | CREATE_VNODE, |
| 443 | CREATE_ELEMENT_VNODE, |
| 444 | CREATE_COMMENT, |
| 445 | CREATE_TEXT, |
| 446 | CREATE_STATIC, |
| 447 | ] |
| 448 | .filter(helper => helpers.includes(helper)) |
| 449 | .map(aliasHelper) |
| 450 | .join(', ') |
| 451 | push(`const { ${staticHelpers} } = _Vue\n`, NewlineType.End) |
| 452 | } |
| 453 | } |
| 454 | } |
| 455 | // generate variables for ssr helpers |
| 456 | if (!__BROWSER__ && ast.ssrHelpers && ast.ssrHelpers.length) { |
| 457 | // ssr guarantees prefixIdentifier: true |
| 458 | push( |
| 459 | `const { ${ast.ssrHelpers |
| 460 | .map(aliasHelper) |
| 461 | .join(', ')} } = require("${ssrRuntimeModuleName}")\n`, |
| 462 | NewlineType.End, |
| 463 | ) |
| 464 | } |
| 465 | genHoists(ast.hoists, context) |