compiler.ts

import * as ts from 'typescript'
import { resolve } from 'path'

const options: ts.CompilerOptions = {
    declaration: true,
    emitDeclarationOnly: true,
    allowJs: true, // I treat jsw as js
    // ...
}

class Host implements ts.CompilerHost {
    private sourceFiles = new Map<string, ts.SourceFile>()

    getSourceFile(
        fileName: string,
        languageVersion: ts.ScriptTarget
    ): ts.SourceFile | undefined {
        const canonical = resolve(this.getCurrentDirectory(), this.getCanonicalFileName(fileName));
        const existing = this.sourceFiles.get(canonical)
        if (existing) return existing;

        const content = this.readFile(canonical);
        if (content === undefined) return undefined;

        const parsed = ts.createSourceFile(canonical, content, languageVersion)
        this.sourceFiles.set(canonical, parsed);

        return parsed;
    }
    getDefaultLibFileName(options: ts.CompilerOptions): string {
        return ts.getDefaultLibFileName(options);
    }
    writeFile(
        fileName: string,
        data: string,
        writeByteOrderMark: boolean,
        _onError?: (message: string) => void,
        _sourceFiles?: readonly ts.SourceFile[]
    ): void {
        // Should probably catch errors.
        ts.sys.writeFile(fileName, data, writeByteOrderMark);
    }
    getCurrentDirectory(): string {
        return ts.sys.getCurrentDirectory();
    }
    getCanonicalFileName(fileName: string): string {
        return this.useCaseSensitiveFileNames() ? fileName : fileName.toLowerCase();
    }
    useCaseSensitiveFileNames(): boolean {
        return ts.sys.useCaseSensitiveFileNames;
    }
    getNewLine(): string {
        return ts.sys.newLine;
    }
    fileExists(fileName: string): boolean {
        if (fileName.endsWith('.js')) {
            return ts.sys.fileExists(fileName + 'w') || ts.sys.fileExists(fileName)
        }
        return ts.sys.fileExists(fileName);
    }
    readFile(fileName: string): string | undefined {
        if (fileName.endsWith('.js') && ts.sys.fileExists(fileName + 'w')) {
            return ts.sys.readFile(fileName + 'w')
        }
        return ts.sys.readFile(fileName)
    }
}

const host = new Host()
const program = ts.createProgram({
    rootNames: ['./src/index.ts'],
    host,
    options,
})

program.emit();