Replace absolute paths by relative, based on baseUrl and paths fields from tsconfig.json

index.js

import * as nodePath from 'path';
import paths from 'tsconfig-paths';
import * as tsconfig from 'tsconfig-extends';
import Project from 'ts-simple-ast';

// use `tsconfig-extends` module cause it can recursively apply "extends" field
const compilerOptions = tsconfig.load_file_sync('./tsconfig.json');
const absoluteBaseUrl = nodePath.join(process.cwd(), compilerOptions.baseUrl);
const matchPathFunc = paths.createMatchPath(absoluteBaseUrl, compilerOptions.paths || {});
const project = new Project({ compilerOptions });

project.addExistingSourceFiles('./src/**/*.{ts,tsx}');

const sourceFiles = project.getSourceFiles();

sourceFiles.forEach(async (sourceFile) => {
    const importExportDeclarations = [
        ...sourceFile.getImportDeclarations(),
        ...sourceFile.getExportDeclarations(),
    ];
    const sourceFileAbsolutePath = sourceFile.getFilePath();
    let sourceFileWasChanged = false;

    for (const declaration of importExportDeclarations) {
        // if module seems like absolute
        if (!declaration.isModuleSpecifierRelative()) {
            const value = declaration.getModuleSpecifierValue();
            // try to find relative module for it
            const absolutePathToDepsModule = matchPathFunc(value);

            // and if relative module really exists
            if (absolutePathToDepsModule) {
                const resultPath = nodePath.relative(sourceFileAbsolutePath, absolutePathToDepsModule);

                // replace absolute to relative
                declaration.setModuleSpecifier(resultPath);
                sourceFileWasChanged = true;
            }
        }
    }

    if (sourceFileWasChanged) {
        await sourceFile.save();
    }
});