diff options
Diffstat (limited to 'node_modules/sucrase/dist/esm/transformers/ESMImportTransformer.js')
| -rw-r--r-- | node_modules/sucrase/dist/esm/transformers/ESMImportTransformer.js | 415 |
1 files changed, 415 insertions, 0 deletions
diff --git a/node_modules/sucrase/dist/esm/transformers/ESMImportTransformer.js b/node_modules/sucrase/dist/esm/transformers/ESMImportTransformer.js new file mode 100644 index 0000000..b45cd3e --- /dev/null +++ b/node_modules/sucrase/dist/esm/transformers/ESMImportTransformer.js @@ -0,0 +1,415 @@ + + + +import {ContextualKeyword} from "../parser/tokenizer/keywords"; +import {TokenType as tt} from "../parser/tokenizer/types"; + +import elideImportEquals from "../util/elideImportEquals"; +import getDeclarationInfo, { + + EMPTY_DECLARATION_INFO, +} from "../util/getDeclarationInfo"; +import getImportExportSpecifierInfo from "../util/getImportExportSpecifierInfo"; +import {getNonTypeIdentifiers} from "../util/getNonTypeIdentifiers"; +import isExportFrom from "../util/isExportFrom"; +import {removeMaybeImportAttributes} from "../util/removeMaybeImportAttributes"; +import shouldElideDefaultExport from "../util/shouldElideDefaultExport"; + +import Transformer from "./Transformer"; + +/** + * Class for editing import statements when we are keeping the code as ESM. We still need to remove + * type-only imports in TypeScript and Flow. + */ +export default class ESMImportTransformer extends Transformer { + + + + + constructor( + tokens, + nameManager, + helperManager, + reactHotLoaderTransformer, + isTypeScriptTransformEnabled, + isFlowTransformEnabled, + keepUnusedImports, + options, + ) { + super();this.tokens = tokens;this.nameManager = nameManager;this.helperManager = helperManager;this.reactHotLoaderTransformer = reactHotLoaderTransformer;this.isTypeScriptTransformEnabled = isTypeScriptTransformEnabled;this.isFlowTransformEnabled = isFlowTransformEnabled;this.keepUnusedImports = keepUnusedImports;; + this.nonTypeIdentifiers = + isTypeScriptTransformEnabled && !keepUnusedImports + ? getNonTypeIdentifiers(tokens, options) + : new Set(); + this.declarationInfo = + isTypeScriptTransformEnabled && !keepUnusedImports + ? getDeclarationInfo(tokens) + : EMPTY_DECLARATION_INFO; + this.injectCreateRequireForImportRequire = Boolean(options.injectCreateRequireForImportRequire); + } + + process() { + // TypeScript `import foo = require('foo');` should always just be translated to plain require. + if (this.tokens.matches3(tt._import, tt.name, tt.eq)) { + return this.processImportEquals(); + } + if ( + this.tokens.matches4(tt._import, tt.name, tt.name, tt.eq) && + this.tokens.matchesContextualAtIndex(this.tokens.currentIndex() + 1, ContextualKeyword._type) + ) { + // import type T = require('T') + this.tokens.removeInitialToken(); + // This construct is always exactly 8 tokens long, so remove the 7 remaining tokens. + for (let i = 0; i < 7; i++) { + this.tokens.removeToken(); + } + return true; + } + if (this.tokens.matches2(tt._export, tt.eq)) { + this.tokens.replaceToken("module.exports"); + return true; + } + if ( + this.tokens.matches5(tt._export, tt._import, tt.name, tt.name, tt.eq) && + this.tokens.matchesContextualAtIndex(this.tokens.currentIndex() + 2, ContextualKeyword._type) + ) { + // export import type T = require('T') + this.tokens.removeInitialToken(); + // This construct is always exactly 9 tokens long, so remove the 8 remaining tokens. + for (let i = 0; i < 8; i++) { + this.tokens.removeToken(); + } + return true; + } + if (this.tokens.matches1(tt._import)) { + return this.processImport(); + } + if (this.tokens.matches2(tt._export, tt._default)) { + return this.processExportDefault(); + } + if (this.tokens.matches2(tt._export, tt.braceL)) { + return this.processNamedExports(); + } + if ( + this.tokens.matches2(tt._export, tt.name) && + this.tokens.matchesContextualAtIndex(this.tokens.currentIndex() + 1, ContextualKeyword._type) + ) { + // export type {a}; + // export type {a as b}; + // export type {a} from './b'; + // export type * from './b'; + // export type * as ns from './b'; + this.tokens.removeInitialToken(); + this.tokens.removeToken(); + if (this.tokens.matches1(tt.braceL)) { + while (!this.tokens.matches1(tt.braceR)) { + this.tokens.removeToken(); + } + this.tokens.removeToken(); + } else { + // * + this.tokens.removeToken(); + if (this.tokens.matches1(tt._as)) { + // as + this.tokens.removeToken(); + // ns + this.tokens.removeToken(); + } + } + // Remove type re-export `... } from './T'` + if ( + this.tokens.matchesContextual(ContextualKeyword._from) && + this.tokens.matches1AtIndex(this.tokens.currentIndex() + 1, tt.string) + ) { + this.tokens.removeToken(); + this.tokens.removeToken(); + removeMaybeImportAttributes(this.tokens); + } + return true; + } + return false; + } + + processImportEquals() { + const importName = this.tokens.identifierNameAtIndex(this.tokens.currentIndex() + 1); + if (this.shouldAutomaticallyElideImportedName(importName)) { + // If this name is only used as a type, elide the whole import. + elideImportEquals(this.tokens); + } else if (this.injectCreateRequireForImportRequire) { + // We're using require in an environment (Node ESM) that doesn't provide + // it as a global, so generate a helper to import it. + // import -> const + this.tokens.replaceToken("const"); + // Foo + this.tokens.copyToken(); + // = + this.tokens.copyToken(); + // require + this.tokens.replaceToken(this.helperManager.getHelperName("require")); + } else { + // Otherwise, just switch `import` to `const`. + this.tokens.replaceToken("const"); + } + return true; + } + + processImport() { + if (this.tokens.matches2(tt._import, tt.parenL)) { + // Dynamic imports don't need to be transformed. + return false; + } + + const snapshot = this.tokens.snapshot(); + const allImportsRemoved = this.removeImportTypeBindings(); + if (allImportsRemoved) { + this.tokens.restoreToSnapshot(snapshot); + while (!this.tokens.matches1(tt.string)) { + this.tokens.removeToken(); + } + this.tokens.removeToken(); + removeMaybeImportAttributes(this.tokens); + if (this.tokens.matches1(tt.semi)) { + this.tokens.removeToken(); + } + } + return true; + } + + /** + * Remove type bindings from this import, leaving the rest of the import intact. + * + * Return true if this import was ONLY types, and thus is eligible for removal. This will bail out + * of the replacement operation, so we can return early here. + */ + removeImportTypeBindings() { + this.tokens.copyExpectedToken(tt._import); + if ( + this.tokens.matchesContextual(ContextualKeyword._type) && + !this.tokens.matches1AtIndex(this.tokens.currentIndex() + 1, tt.comma) && + !this.tokens.matchesContextualAtIndex(this.tokens.currentIndex() + 1, ContextualKeyword._from) + ) { + // This is an "import type" statement, so exit early. + return true; + } + + if (this.tokens.matches1(tt.string)) { + // This is a bare import, so we should proceed with the import. + this.tokens.copyToken(); + return false; + } + + // Skip the "module" token in import reflection. + if ( + this.tokens.matchesContextual(ContextualKeyword._module) && + this.tokens.matchesContextualAtIndex(this.tokens.currentIndex() + 2, ContextualKeyword._from) + ) { + this.tokens.copyToken(); + } + + let foundNonTypeImport = false; + let foundAnyNamedImport = false; + let needsComma = false; + + // Handle default import. + if (this.tokens.matches1(tt.name)) { + if (this.shouldAutomaticallyElideImportedName(this.tokens.identifierName())) { + this.tokens.removeToken(); + if (this.tokens.matches1(tt.comma)) { + this.tokens.removeToken(); + } + } else { + foundNonTypeImport = true; + this.tokens.copyToken(); + if (this.tokens.matches1(tt.comma)) { + // We're in a statement like: + // import A, * as B from './A'; + // or + // import A, {foo} from './A'; + // where the `A` is being kept. The comma should be removed if an only + // if the next part of the import statement is elided, but that's hard + // to determine at this point in the code. Instead, always remove it + // and set a flag to add it back if necessary. + needsComma = true; + this.tokens.removeToken(); + } + } + } + + if (this.tokens.matches1(tt.star)) { + if (this.shouldAutomaticallyElideImportedName(this.tokens.identifierNameAtRelativeIndex(2))) { + this.tokens.removeToken(); + this.tokens.removeToken(); + this.tokens.removeToken(); + } else { + if (needsComma) { + this.tokens.appendCode(","); + } + foundNonTypeImport = true; + this.tokens.copyExpectedToken(tt.star); + this.tokens.copyExpectedToken(tt.name); + this.tokens.copyExpectedToken(tt.name); + } + } else if (this.tokens.matches1(tt.braceL)) { + if (needsComma) { + this.tokens.appendCode(","); + } + this.tokens.copyToken(); + while (!this.tokens.matches1(tt.braceR)) { + foundAnyNamedImport = true; + const specifierInfo = getImportExportSpecifierInfo(this.tokens); + if ( + specifierInfo.isType || + this.shouldAutomaticallyElideImportedName(specifierInfo.rightName) + ) { + while (this.tokens.currentIndex() < specifierInfo.endIndex) { + this.tokens.removeToken(); + } + if (this.tokens.matches1(tt.comma)) { + this.tokens.removeToken(); + } + } else { + foundNonTypeImport = true; + while (this.tokens.currentIndex() < specifierInfo.endIndex) { + this.tokens.copyToken(); + } + if (this.tokens.matches1(tt.comma)) { + this.tokens.copyToken(); + } + } + } + this.tokens.copyExpectedToken(tt.braceR); + } + + if (this.keepUnusedImports) { + return false; + } + if (this.isTypeScriptTransformEnabled) { + return !foundNonTypeImport; + } else if (this.isFlowTransformEnabled) { + // In Flow, unlike TS, `import {} from 'foo';` preserves the import. + return foundAnyNamedImport && !foundNonTypeImport; + } else { + return false; + } + } + + shouldAutomaticallyElideImportedName(name) { + return ( + this.isTypeScriptTransformEnabled && + !this.keepUnusedImports && + !this.nonTypeIdentifiers.has(name) + ); + } + + processExportDefault() { + if ( + shouldElideDefaultExport( + this.isTypeScriptTransformEnabled, + this.keepUnusedImports, + this.tokens, + this.declarationInfo, + ) + ) { + // If the exported value is just an identifier and should be elided by TypeScript + // rules, then remove it entirely. It will always have the form `export default e`, + // where `e` is an identifier. + this.tokens.removeInitialToken(); + this.tokens.removeToken(); + this.tokens.removeToken(); + return true; + } + + const alreadyHasName = + this.tokens.matches4(tt._export, tt._default, tt._function, tt.name) || + // export default async function + (this.tokens.matches5(tt._export, tt._default, tt.name, tt._function, tt.name) && + this.tokens.matchesContextualAtIndex( + this.tokens.currentIndex() + 2, + ContextualKeyword._async, + )) || + this.tokens.matches4(tt._export, tt._default, tt._class, tt.name) || + this.tokens.matches5(tt._export, tt._default, tt._abstract, tt._class, tt.name); + + if (!alreadyHasName && this.reactHotLoaderTransformer) { + // This is a plain "export default E" statement and we need to assign E to a variable. + // Change "export default E" to "let _default; export default _default = E" + const defaultVarName = this.nameManager.claimFreeName("_default"); + this.tokens.replaceToken(`let ${defaultVarName}; export`); + this.tokens.copyToken(); + this.tokens.appendCode(` ${defaultVarName} =`); + this.reactHotLoaderTransformer.setExtractedDefaultExportName(defaultVarName); + return true; + } + return false; + } + + /** + * Handle a statement with one of these forms: + * export {a, type b}; + * export {c, type d} from 'foo'; + * + * In both cases, any explicit type exports should be removed. In the first + * case, we also need to handle implicit export elision for names declared as + * types. In the second case, we must NOT do implicit named export elision, + * but we must remove the runtime import if all exports are type exports. + */ + processNamedExports() { + if (!this.isTypeScriptTransformEnabled) { + return false; + } + this.tokens.copyExpectedToken(tt._export); + this.tokens.copyExpectedToken(tt.braceL); + + const isReExport = isExportFrom(this.tokens); + let foundNonTypeExport = false; + while (!this.tokens.matches1(tt.braceR)) { + const specifierInfo = getImportExportSpecifierInfo(this.tokens); + if ( + specifierInfo.isType || + (!isReExport && this.shouldElideExportedName(specifierInfo.leftName)) + ) { + // Type export, so remove all tokens, including any comma. + while (this.tokens.currentIndex() < specifierInfo.endIndex) { + this.tokens.removeToken(); + } + if (this.tokens.matches1(tt.comma)) { + this.tokens.removeToken(); + } + } else { + // Non-type export, so copy all tokens, including any comma. + foundNonTypeExport = true; + while (this.tokens.currentIndex() < specifierInfo.endIndex) { + this.tokens.copyToken(); + } + if (this.tokens.matches1(tt.comma)) { + this.tokens.copyToken(); + } + } + } + this.tokens.copyExpectedToken(tt.braceR); + + if (!this.keepUnusedImports && isReExport && !foundNonTypeExport) { + // This is a type-only re-export, so skip evaluating the other module. Technically this + // leaves the statement as `export {}`, but that's ok since that's a no-op. + this.tokens.removeToken(); + this.tokens.removeToken(); + removeMaybeImportAttributes(this.tokens); + } + + return true; + } + + /** + * ESM elides all imports with the rule that we only elide if we see that it's + * a type and never see it as a value. This is in contrast to CJS, which + * elides imports that are completely unknown. + */ + shouldElideExportedName(name) { + return ( + this.isTypeScriptTransformEnabled && + !this.keepUnusedImports && + this.declarationInfo.typeDeclarations.has(name) && + !this.declarationInfo.valueDeclarations.has(name) + ); + } +} |