sucrase/dist/src/transformers/ImportTransformer.mjs

Super-fast alternative to Babel for when you can target modern JS runtimes

import { IdentifierRole } from "../../sucrase-babylon/tokenizer";
import Transformer from "./Transformer";
export default class ImportTransformer extends Transformer {
    constructor(rootTransformer, tokens, importProcessor, shouldAddModuleExports) {
        super();
        this.rootTransformer = rootTransformer;
        this.tokens = tokens;
        this.importProcessor = importProcessor;
        this.shouldAddModuleExports = shouldAddModuleExports;
        this.hadExport = false;
        this.hadNamedExport = false;
        this.hadDefaultExport = false;
    }
    getPrefixCode() {
        let prefix = '"use strict";';
        prefix += this.importProcessor.getPrefixCode();
        if (this.hadExport) {
            prefix += 'Object.defineProperty(exports, "__esModule", {value: true});';
        }
        return prefix;
    }
    getSuffixCode() {
        if (this.shouldAddModuleExports && this.hadDefaultExport && !this.hadNamedExport) {
            return "\nmodule.exports = exports.default;\n";
        }
        return "";
    }
    process() {
        if (this.tokens.matches(["import", "name", "="])) {
            this.tokens.replaceToken("const");
            return true;
        }
        if (this.tokens.matches(["import"])) {
            this.processImport();
            return true;
        }
        if (this.tokens.matches(["export", "="])) {
            this.tokens.replaceToken("module.exports");
            return true;
        }
        if (this.tokens.matches(["export"]) && !this.tokens.currentToken().isType) {
            this.hadExport = true;
            return this.processExport();
        }
        if (this.tokens.matches(["name"]) || this.tokens.matches(["jsxName"])) {
            return this.processIdentifier();
        }
        if (this.tokens.matches(["="])) {
            return this.processAssignment();
        }
        return false;
    }
    /**
     * Transform this:
     * import foo, {bar} from 'baz';
     * into
     * var _baz = require('baz'); var _baz2 = _interopRequireDefault(_baz);
     *
     * The import code was already generated in the import preprocessing step, so
     * we just need to look it up.
     */
    processImport() {
        if (this.tokens.matches(["import", "("])) {
            this.tokens.replaceToken("Promise.resolve().then(() => require");
            const contextId = this.tokens.currentToken().contextId;
            if (contextId == null) {
                throw new Error("Expected context ID on dynamic import invocation.");
            }
            this.tokens.copyToken();
            while (!this.tokens.matchesContextIdAndLabel(")", contextId)) {
                this.rootTransformer.processToken();
            }
            this.tokens.replaceToken("))");
            return;
        }
        const wasOnlyTypes = this.removeImportAndDetectIfType();
        if (wasOnlyTypes) {
            this.tokens.removeToken();
        }
        else {
            const path = this.tokens.currentToken().value;
            this.tokens.replaceTokenTrimmingLeftWhitespace(this.importProcessor.claimImportCode(path));
            this.tokens.appendCode(this.importProcessor.claimImportCode(path));
        }
        if (this.tokens.matches([";"])) {
            this.tokens.removeToken();
        }
    }
    /**
     * Erase this import, and if it was either of the form "import type" or
     * contained only "type". Such imports should not even do a side-effect
     * import.
     *
     * The position should end at the import string.
     */
    removeImportAndDetectIfType() {
        this.tokens.removeInitialToken();
        if (this.tokens.matchesName("type") &&
            !this.tokens.matchesAtIndex(this.tokens.currentIndex() + 1, [","]) &&
            !this.tokens.matchesNameAtIndex(this.tokens.currentIndex() + 1, "from")) {
            // This is an "import type" statement, so exit early.
            this.removeRemainingImport();
            return true;
        }
        if (this.tokens.matches(["name"]) || this.tokens.matches(["*"])) {
            // We have a default import or namespace import, so there must be some
            // non-type import.
            this.removeRemainingImport();
            return false;
        }
        if (this.tokens.matches(["string"])) {
            // This is a bare import, so we should proceed with the import.
            return false;
        }
        let foundNonType = false;
        while (!this.tokens.matches(["string"])) {
            // Check if any named imports are of the form "foo" or "foo as bar", with
            // no leading "type".
            if ((!foundNonType && this.tokens.matches(["{"])) || this.tokens.matches([","])) {
                this.tokens.removeToken();
                if (this.tokens.matches(["name", ","]) ||
                    this.tokens.matches(["name", "}"]) ||
                    this.tokens.matches(["name", "name", "name", ","]) ||
                    this.tokens.matches(["name", "name", "name", "}"])) {
                    foundNonType = true;
                }
            }
            this.tokens.removeToken();
        }
        return !foundNonType;
    }
    removeRemainingImport() {
        while (!this.tokens.matches(["string"])) {
            this.tokens.removeToken();
        }
    }
    processIdentifier() {
        const token = this.tokens.currentToken();
        if (token.shadowsGlobal) {
            return false;
        }
        if (token.identifierRole === IdentifierRole.ObjectShorthand) {
            return this.processObjectShorthand();
        }
        if (token.identifierRole !== IdentifierRole.Access) {
            return false;
        }
        const replacement = this.importProcessor.getIdentifierReplacement(token.value);
        if (!replacement) {
            return false;
        }
        // For now, always use the (0, a) syntax so that non-expression replacements
        // are more likely to become syntax errors.
        this.tokens.replaceToken(`(0, ${replacement})`);
        return true;
    }
    processObjectShorthand() {
        const identifier = this.tokens.currentToken().value;
        const replacement = this.importProcessor.getIdentifierReplacement(identifier);
        if (!replacement) {
            return false;
        }
        this.tokens.replaceToken(`${identifier}: ${replacement}`);
        return true;
    }
    processExport() {
        if (this.tokens.matches(["export", "enum"]) ||
            this.tokens.matches(["export", "const", "enum"])) {
            // Let the TypeScript transform handle it.
            return false;
        }
        if (this.tokens.matches(["export", "default"])) {
            this.processExportDefault();
            this.hadDefaultExport = true;
            return true;
        }
        this.hadNamedExport = true;
        if (this.tokens.matches(["export", "var"]) ||
            this.tokens.matches(["export", "let"]) ||
            this.tokens.matches(["export", "const"])) {
            this.processExportVar();
            return true;
        }
        else if (this.tokens.matches(["export", "function"]) ||
            this.tokens.matches(["export", "name", "function"])) {
            this.processExportFunction();
            return true;
        }
        else if (this.tokens.matches(["export", "class"]) ||
            this.tokens.matches(["export", "abstract", "class"])) {
            this.processExportClass();
            return true;
        }
        else if (this.tokens.matches(["export", "{"])) {
            this.processExportBindings();
            return true;
        }
        else if (this.tokens.matches(["export", "*"])) {
            this.processExportStar();
            return true;
        }
        else {
            throw new Error("Unrecognized export syntax.");
        }
    }
    processAssignment() {
        const index = this.tokens.currentIndex();
        const identifierToken = this.tokens.tokens[index - 1];
        if (identifierToken.type.label !== "name") {
            return false;
        }
        if (this.tokens.matchesAtIndex(index - 2, ["."])) {
            return false;
        }
        if (index - 2 >= 0 &&
            ["var", "let", "const"].includes(this.tokens.tokens[index - 2].type.label)) {
            // Declarations don't need an extra assignment. This doesn't avoid the
            // assignment for comma-separated declarations, but it's still correct
            // since the assignment is just redundant.
            return false;
        }
        const exportedName = this.importProcessor.resolveExportBinding(identifierToken.value);
        if (!exportedName) {
            return false;
        }
        this.tokens.copyToken();
        this.tokens.appendCode(` exports.${exportedName} =`);
        return true;
    }
    processExportDefault() {
        if (this.tokens.matches(["export", "default", "function", "name"]) ||
            // export default aysnc function
            this.tokens.matches(["export", "default", "name", "function", "name"])) {
            this.tokens.removeInitialToken();
            this.tokens.removeToken();
            // Named function export case: change it to a top-level function
            // declaration followed by exports statement.
            const name = this.processNamedFunction();
            this.tokens.appendCode(` exports.default = ${name};`);
        }
        else if (this.tokens.matches(["export", "default", "class", "name"]) ||
            this.tokens.matches(["export", "default", "abstract", "class", "name"])) {
            this.tokens.removeInitialToken();
            this.tokens.removeToken();
            if (this.tokens.matches(["abstract"])) {
                this.tokens.removeToken();
            }
            const name = this.rootTransformer.processNamedClass();
            this.tokens.appendCode(` exports.default = ${name};`);
        }
        else {
            this.tokens.replaceToken("exports.");
            this.tokens.copyToken();
            this.tokens.appendCode(" =");
        }
    }
    /**
     * Transform this:
     * export const x = 1;
     * into this:
     * const x = exports.x = 1;
     */
    processExportVar() {
        this.tokens.replaceToken("");
        this.tokens.copyToken();
        if (!this.tokens.matches(["name"])) {
            throw new Error("Expected a regular identifier after export var/let/const.");
        }
        const name = this.tokens.currentToken().value;
        this.tokens.copyToken();
        this.tokens.appendCode(` = exports.${name}`);
    }
    /**
     * Transform this:
     * export function foo() {}
     * into this:
     * function foo() {} exports.foo = foo;
     */
    processExportFunction() {
        this.tokens.replaceToken("");
        const name = this.processNamedFunction();
        this.tokens.appendCode(` exports.${name} = ${name};`);
    }
    /**
     * Skip past a function with a name and return that name.
     */
    processNamedFunction() {
        if (this.tokens.matches(["function"])) {
            this.tokens.copyToken();
        }
        else if (this.tokens.matches(["name", "function"])) {
            if (this.tokens.currentToken().value !== "async") {
                throw new Error("Expected async keyword in function export.");
            }
            this.tokens.copyToken();
            this.tokens.copyToken();
        }
        if (!this.tokens.matches(["name"])) {
            throw new Error("Expected identifier for exported function name.");
        }
        const name = this.tokens.currentToken().value;
        this.tokens.copyToken();
        if (this.tokens.currentToken().isType) {
            this.tokens.removeInitialToken();
            while (this.tokens.currentToken().isType) {
                this.tokens.removeToken();
            }
        }
        this.tokens.copyExpectedToken("(");
        this.rootTransformer.processBalancedCode();
        this.tokens.copyExpectedToken(")");
        this.rootTransformer.processPossibleTypeRange();
        this.tokens.copyExpectedToken("{");
        this.rootTransformer.processBalancedCode();
        this.tokens.copyExpectedToken("}");
        return name;
    }
    /**
     * Transform this:
     * export class A {}
     * into this:
     * class A {} exports.A = A;
     */
    processExportClass() {
        this.tokens.removeInitialToken();
        if (this.tokens.matches(["abstract"])) {
            this.tokens.removeToken();
        }
        const name = this.rootTransformer.processNamedClass();
        this.tokens.appendCode(` exports.${name} = ${name};`);
    }
    /**
     * Transform this:
     * export {a, b as c};
     * into this:
     * exports.a = a; exports.c = b;
     *
     * OR
     *
     * Transform this:
     * export {a, b as c} from './foo';
     * into the pre-generated Object.defineProperty code from the ImportProcessor.
     */
    processExportBindings() {
        this.tokens.removeInitialToken();
        this.tokens.removeToken();
        const exportStatements = [];
        while (true) {
            const localName = this.tokens.currentToken().value;
            let exportedName;
            this.tokens.removeToken();
            if (this.tokens.matchesName("as")) {
                this.tokens.removeToken();
                exportedName = this.tokens.currentToken().value;
                this.tokens.removeToken();
            }
            else {
                exportedName = localName;
            }
            const newLocalName = this.importProcessor.getIdentifierReplacement(localName);
            exportStatements.push(`exports.${exportedName} = ${newLocalName || localName};`);
            if (this.tokens.matches(["}"])) {
                this.tokens.removeToken();
                break;
            }
            if (this.tokens.matches([",", "}"])) {
                this.tokens.removeToken();
                this.tokens.removeToken();
                break;
            }
            else if (this.tokens.matches([","])) {
                this.tokens.removeToken();
            }
            else {
                throw new Error(`Unexpected token: ${JSON.stringify(this.tokens.currentToken())}`);
            }
        }
        if (this.tokens.matchesName("from")) {
            // This is an export...from, so throw away the normal named export code
            // and use the Object.defineProperty code from ImportProcessor.
            this.tokens.removeToken();
            const path = this.tokens.currentToken().value;
            this.tokens.replaceTokenTrimmingLeftWhitespace(this.importProcessor.claimImportCode(path));
        }
        else {
            // This is a normal named export, so use that.
            this.tokens.appendCode(exportStatements.join(" "));
        }
        if (this.tokens.matches([";"])) {
            this.tokens.removeToken();
        }
    }
    processExportStar() {
        this.tokens.removeInitialToken();
        while (!this.tokens.matches(["string"])) {
            this.tokens.removeToken();
        }
        const path = this.tokens.currentToken().value;
        this.tokens.replaceTokenTrimmingLeftWhitespace(this.importProcessor.claimImportCode(path));
        if (this.tokens.matches([";"])) {
            this.tokens.removeToken();
        }
    }
}