feat: add packageJson setting

- closes #7258
- closes #6824
- closes #4828
- part of #2242
- better message for #2884

Author: dummdidumm

.changeset/nine-spoons-attack.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/package': minor
+---
+
+feat: add `packageJson` setting to adjust final `package.json`

documentation/docs/30-advanced/70-packaging.md

@@ -2,8 +2,6 @@
 title: Packaging
 ---
 
-> `svelte-package` is currently experimental. Non-backward compatible changes may occur in any future release.
-
 You can use SvelteKit to build apps as well as component libraries, using the `@sveltejs/package` package (`npm create svelte` has an option to set this up for you).
 
 When you're creating an app, the contents of `src/routes` is the public-facing stuff; [`src/lib`](modules#$lib) contains your app's internal library.
@@ -12,11 +10,11 @@ A component library has the exact same structure as a SvelteKit app, except that
 
 Running the `svelte-package` command from `@sveltejs/package` will take the contents of `src/lib` and generate a `package` directory (which can be [configured](configuration)) containing the following:
 
-- All the files in `src/lib`, unless you [configure](configuration) custom `include`/`exclude` options. Svelte components will be preprocessed, TypeScript files will be transpiled to JavaScript.
-- Type definitions (`d.ts` files) which are generated for Svelte, JavaScript and TypeScript files. You need to install `typescript >= 4.0.0` for this. Type definitions are placed next to their implementation, hand-written `d.ts` files are copied over as is. You can [disable generation](configuration), but we strongly recommend against it — people using your library might use TypeScript, for which they require these type definition files.
-- A `package.json` copied from the project root with all fields except `"scripts"`, `"publishConfig.directory"` and `"publishConfig.linkDirectory"`. The `"dependencies"` field is included, which means you should add packages that you only need for your documentation or demo site to `"devDependencies"`. A `"type": "module"` and an `"exports"` field will be added if it's not defined in the original file.
+- All the files in `src/lib`, unless you [configure](configuration) the custom `files` option. Svelte components will be preprocessed, TypeScript files will be transpiled to JavaScript.
+- Type definitions (`d.ts` files) which are generated for Svelte, JavaScript and TypeScript files. You need to install `typescript >= 4.0.0` for this. Type definitions are placed next to their implementation, hand-written `d.ts` files are copied over as is. You can [disable generation](configuration) by setting `emitTypes: false`, but we strongly recommend against it — people using your library might use TypeScript, for which they require these type definition files.
+- A `package.json` copied from the project root with all fields except `"scripts"`, `"publishConfig.directory"` and `"publishConfig.linkDirectory"`. The `"dependencies"` field is included, which means you should add packages that you only need for your documentation or demo site to `"devDependencies"`. A `"type": "module"` and an `"exports"` field will be added if it's not defined in the original file. You can customize the final `package.json` contents through the `packageJson` option, which is passed the original and generated `package.json`. If you return `undefined`, the `package.json` will not be written to the output directory.
 
-The `"exports"` field contains the package's entry points. By default, all files in `src/lib` will be treated as an entry point unless they start with (or live in a directory that starts with) an underscore, but you can [configure](configuration) this behaviour. If you have a `src/lib/index.js` or `src/lib/index.svelte` file, it will be treated as the package root.
+The `"exports"` field contains the package's entry points. By default, all files in `src/lib` will be treated as an entry point unless they start with (or live in a directory that starts with) an underscore, but you can [configure](configuration) this behaviour through the `packageJson` option. If you have a `src/lib/index.js` or `src/lib/index.svelte` file, it will be treated as the package root.
 
 For example, if you had a `src/lib/Foo.svelte` component and a `src/lib/index.js` module that re-exported it, a consumer of your library could do either of the following:
 

packages/package/src/config.js

@@ -24,13 +24,26 @@ export async function load_config({ cwd = process.cwd() } = {}) {
  * @returns {import('./types').ValidatedConfig}
  */
 function process_config(config, { cwd = process.cwd() } = {}) {
+	let warned = false;
+
 	return {
 		extensions: config.extensions ?? ['.svelte'],
 		kit: config.kit,
 		package: {
 			source: path.resolve(cwd, config.kit?.files?.lib ?? config.package?.source ?? 'src/lib'),
 			dir: config.package?.dir ?? 'package',
-			exports: config.package?.exports ?? ((filepath) => !/^_|\/_|\.d\.ts$/.test(filepath)),
+			exports: config.package?.exports
+				? (filepath) => {
+						if (!warned) {
+							console.warn(
+								'The `package.exports` option is deprecated. Use `package.packageJson` instead.'
+							);
+							warned = true;
+						}
+						return /** @type {any} */ (config.package).exports(filepath);
+				  }
+				: (filepath) => !/^_|\/_|\.d\.ts$/.test(filepath),
+			packageJson: config.package?.packageJson ?? ((_, pkg) => pkg),
 			files: config.package?.files ?? (() => true),
 			emitTypes: config.package?.emitTypes ?? true
 		},

packages/package/src/index.js

@@ -4,7 +4,15 @@ import colors from 'kleur';
 import chokidar from 'chokidar';
 import { preprocess } from 'svelte/compiler';
 import { copy, mkdirp, rimraf } from './filesystem.js';
-import { analyze, generate_pkg, resolve_lib_alias, scan, strip_lang_tags, write } from './utils.js';
+import {
+	analyze,
+	generate_pkg,
+	resolve_lib_alias,
+	scan,
+	strip_lang_tags,
+	write,
+	write_if_changed
+} from './utils.js';
 import { emit_dts, transpile_ts } from './typescript.js';
 
 const essential_files = ['README', 'LICENSE', 'CHANGELOG', '.gitignore', '.npmignore'];
@@ -30,39 +38,12 @@ export async function build(config, cwd = process.cwd()) {
 		await emit_dts(config, cwd, files);
 	}
 
-	const pkg = generate_pkg(cwd, files);
+	const { pkg, pkg_name } = generate_pkg(cwd, config.package.packageJson, files);
 
-	if (!pkg.dependencies?.svelte && !pkg.peerDependencies?.svelte) {
-		console.warn(
-			'Svelte libraries should include "svelte" in either "dependencies" or "peerDependencies".'
-		);
+	if (pkg) {
+		write_if_changed(join(dir, 'package.json'), JSON.stringify(pkg, null, 2));
 	}
 
-	if (!pkg.svelte && files.some((file) => file.is_svelte)) {
-		// Several heuristics in Kit/vite-plugin-svelte to tell Vite to mark Svelte packages
-		// rely on the "svelte" property. Vite/Rollup/Webpack plugin can all deal with it.
-		// See https://github.com/sveltejs/kit/issues/1959 for more info and related threads.
-		if (pkg.exports['.']) {
-			const svelte_export =
-				typeof pkg.exports['.'] === 'string'
-					? pkg.exports['.']
-					: pkg.exports['.'].import || pkg.exports['.'].default;
-			if (svelte_export) {
-				pkg.svelte = svelte_export;
-			} else {
-				console.warn(
-					'Cannot generate a "svelte" entry point because the "." entry in "exports" is not a string. If you set it by hand, please also set one of the options as a "svelte" entry point\n'
-				);
-			}
-		} else {
-			console.warn(
-				'Cannot generate a "svelte" entry point because the "." entry in "exports" is missing. Please specify one or set a "svelte" entry point yourself\n'
-			);
-		}
-	}
-
-	write(join(dir, 'package.json'), JSON.stringify(pkg, null, 2));
-
 	for (const file of files) {
 		await process_file(config, file);
 	}
@@ -83,8 +64,10 @@ export async function build(config, cwd = process.cwd()) {
 	const from = relative(cwd, lib);
 	const to = relative(cwd, dir);
 	console.log(colors.bold().green(`${from} -> ${to}`));
-	console.log(`Successfully built '${pkg.name}' package. To publish it to npm:`);
-	console.log(colors.bold().cyan(`  cd ${to}`));
+	console.log(`Successfully built '${pkg_name}' package. To publish it to npm:`);
+	if (pkg) {
+		console.log(colors.bold().cyan(`  cd ${to}`));
+	}
 	console.log(colors.bold().cyan('  npm publish\n'));
 }
 
@@ -98,8 +81,7 @@ export async function watch(config, cwd = process.cwd()) {
 
 	console.log(message);
 
-	const { source: lib } = config.package;
-	const { dir } = config.package;
+	const { dir, source: lib } = config.package;
 
 	/** @type {Array<{ file: import('./types').File, type: string }>} */
 	const pending = [];
@@ -129,7 +111,7 @@ export async function watch(config, cwd = process.cwd()) {
 			pending.length = 0;
 
 			for (const { file, type } of events) {
-				if ((type === 'unlink' || type === 'add') && file.is_exported) {
+				if (type === 'unlink' || type === 'add') {
 					should_update_pkg = true;
 				}
 
@@ -161,9 +143,11 @@ export async function watch(config, cwd = process.cwd()) {
 			}
 
 			if (should_update_pkg) {
-				const pkg = generate_pkg(cwd, files);
-				write(join(dir, 'package.json'), JSON.stringify(pkg, null, 2));
-				console.log('Updated package.json');
+				const pkg = generate_pkg(cwd, config.package.packageJson, files);
+				const changed = write_if_changed(join(dir, 'package.json'), JSON.stringify(pkg, null, 2));
+				if (changed) {
+					console.log('Updated package.json');
+				}
 			}
 
 			if (config.package.emitTypes) {

packages/package/src/utils.js

@@ -66,6 +66,21 @@ export function write(file, contents) {
 	fs.writeFileSync(file, contents);
 }
 
+/** @type {Map<string, string>} */
+let current = new Map();
+/**
+ * @param {string} file
+ * @param {string} contents
+ */
+export function write_if_changed(file, contents) {
+	if (current.get(file) !== contents) {
+		write(file, contents);
+		current.set(file, contents);
+		return true;
+	}
+	return false;
+}
+
 /**
  * @param {import('./types').ValidatedConfig} config
  * @returns {import('./types').File[]}
@@ -106,10 +121,12 @@ export function analyze(config, file) {
 
 /**
  * @param {string} cwd
+ * @param {NonNullable<import('types').PackageConfig['packageJson']>} packageJson
  * @param {import('./types').File[]} files
  */
-export function generate_pkg(cwd, files) {
+export function generate_pkg(cwd, packageJson, files) {
 	const pkg = JSON.parse(fs.readFileSync(path.join(cwd, 'package.json'), 'utf8'));
+	const original = JSON.parse(JSON.stringify(pkg));
 
 	// Remove fields that are specific to the original package.json
 	// See: https://pnpm.io/package_json#publishconfigdirectory
@@ -147,5 +164,37 @@ export function generate_pkg(cwd, files) {
 		}
 	}
 
-	return pkg;
+	if (!pkg.dependencies?.svelte && !pkg.peerDependencies?.svelte) {
+		console.warn(
+			'Svelte libraries should include "svelte" in either "dependencies" or "peerDependencies".'
+		);
+	}
+
+	if (!pkg.svelte && files.some((file) => file.is_svelte)) {
+		// Several heuristics in Kit/vite-plugin-svelte to tell Vite to mark Svelte packages
+		// rely on the "svelte" property. Vite/Rollup/Webpack plugin can all deal with it.
+		// See https://github.com/sveltejs/kit/issues/1959 for more info and related threads.
+		if (pkg.exports['.']) {
+			const svelte_export =
+				typeof pkg.exports['.'] === 'string'
+					? pkg.exports['.']
+					: pkg.exports['.'].svelte || pkg.exports['.'].import || pkg.exports['.'].default;
+			if (svelte_export) {
+				pkg.svelte = svelte_export;
+			} else {
+				console.warn(
+					'Cannot generate a "svelte" entry point because the "." entry in "exports" is not a string. If you set it by hand, please also set one of the options as a "svelte" entry point in your package.json\n' +
+						'Example: { ..., "svelte": "./index.svelte" } }\n'
+				);
+			}
+		} else {
+			console.warn(
+				'Cannot generate a "svelte" entry point because the "." entry in "exports" is missing. Please specify one or set a "svelte" entry point yourself in your package.json\n' +
+					'Example: { ..., "svelte": "./index.svelte" } }\n'
+			);
+		}
+	}
+
+	const final = packageJson(original, pkg);
+	return { pkg: packageJson(original, pkg), pkg_name: final?.name ?? original.name };
 }

packages/package/test/fixtures/package-json-omit/expected/index.d.ts

@@ -0,0 +1 @@
+export const foo: true;

packages/package/test/fixtures/package-json-omit/expected/index.js

@@ -0,0 +1 @@
+export const foo = true;

packages/package/test/fixtures/package-json-omit/jsconfig.json

@@ -0,0 +1 @@
+{}

packages/package/test/fixtures/package-json-omit/package.json

@@ -0,0 +1,7 @@
+{
+	"name": "package-json-omit",
+	"private": true,
+	"version": "1.0.0",
+	"description": "omits package json",
+	"type": "module"
+}

packages/package/test/fixtures/package-json-omit/src/lib/index.js

@@ -0,0 +1 @@
+export const foo = true;