Test and document advanced form attributes

README.md

@@ -40,9 +40,29 @@ const swup = new Swup({
 
 ## Server response
 
+The server response must be a valid page with all containers to be replaced by swup.
+
+## Form attributes
+
 Action, method and encoding type attributes set on the form are respected.
 
-The server response must be a valid page with all containers to be replaced by swup.
+[Externally associated inputs](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input#form) are
+supported. Inputs and submit buttons that live outside the form but reference it via `form="form-id"` are
+included in the submission.
+
+Submitter overrides are supported. If the submitter is a button, its `formaction`, `formmethod`, `formenctype`
+and `formtarget` attributes override the form's corresponding attributes, matching native browser behavior.
+
+```html
+<!-- The form itself, handled by swup -->
+<form id="search" action="/search" data-swup-form></form>
+
+<!-- External input associated with the form above -->
+<input name="q" form="search" />
+
+<!-- External submitter associated with the form above, overriding the form action -->
+<button type="submit" form="search" formaction="/search/advanced">Search</button>
+```
 
 ## Custom animations
 
@@ -84,6 +104,10 @@ If you give a form an additional attribute `[data-swup-inline-form]`, swup will:
 }
 ```
 
+> **Note** Inline forms only replace the form's own container. Controls associated with an
+> inline form via the `form` attribute but placed outside of it are **not**
+> re-rendered on submit.
+
 ## Options
 
 ### `formSelector`

tests/unit/forms.test.ts

@@ -15,6 +15,8 @@ const createButton = (html: string) => {
 	return new window.DOMParser().parseFromString(html, 'text/html').querySelector('button')!;
 };
 
+const parseDoc = (html: string) => new window.DOMParser().parseFromString(html, 'text/html');
+
 describe('appendQueryParams', () => {
 	const empty = new FormData();
 	const data = new FormData();
@@ -225,3 +227,60 @@ describe('getFormInfo', () => {
 		});
 	});
 });
+
+describe('getFormInfo with the form attribute', () => {
+	it('includes inputs associated via the form attribute in GET params', () => {
+		const doc = parseDoc(
+			'<form id="f" action="/path#anchor"></form>' +
+				'<input type="hidden" name="a" value="b" form="f">'
+		);
+		const form = doc.querySelector('form')!;
+		expect(getFormInfo(form)).toMatchObject({
+			href: 'http://localhost:3000/path?a=b#anchor',
+			url: '/path?a=b',
+			hash: '#anchor',
+			method: 'GET'
+		});
+	});
+
+	it('includes inputs associated via the form attribute in POST body', () => {
+		const doc = parseDoc(
+			'<form id="f" action="/path" method="post"></form>' +
+				'<input type="hidden" name="a" value="b" form="f">'
+		);
+		const form = doc.querySelector('form')!;
+		expect(getFormInfo(form)).toMatchObject({
+			url: '/path',
+			method: 'POST',
+			body: new URLSearchParams({ a: 'b' })
+		});
+	});
+
+	it('includes the value of an externally associated submitter', () => {
+		const doc = parseDoc(
+			'<form id="f" action="/path" method="post"></form>' +
+				'<button type="submit" form="f" name="btn" value="go">go</button>'
+		);
+		const form = doc.querySelector('form')!;
+		const submitter = doc.querySelector('button');
+		expect(getFormInfo(form, submitter)).toMatchObject({
+			url: '/path',
+			method: 'POST',
+			body: new URLSearchParams({ btn: 'go' })
+		});
+	});
+
+	it('reads formaction/formmethod from an externally associated submitter', () => {
+		const doc = parseDoc(
+			'<form id="f" action="/path"></form>' +
+				'<button type="submit" form="f" formaction="/other" formmethod="post">go</button>'
+		);
+		const form = doc.querySelector('form')!;
+		const submitter = doc.querySelector('button');
+		expect(getFormInfo(form, submitter)).toMatchObject({
+			action: 'http://localhost:3000/other',
+			url: '/other',
+			method: 'POST'
+		});
+	});
+});

tests/unit/plugin.test.ts

@@ -11,6 +11,14 @@ const createForm = (html: string) => {
 	return form;
 };
 
+const appendToBody = <T extends Element = HTMLElement>(html: string) => {
+	const wrapper = document.createElement('div');
+	wrapper.innerHTML = html;
+	const el = wrapper.firstElementChild as T;
+	document.body.appendChild(el);
+	return el;
+};
+
 const submitForm = (form: HTMLFormElement, submitter?: HTMLButtonElement | null, key?: string) => {
 	if (key) {
 		document.dispatchEvent(new KeyboardEvent('keydown', { key }));
@@ -45,6 +53,7 @@ describe('SwupFormsPlugin', () => {
 	afterEach(() => {
 		swup.unuse(plugin);
 		swup.destroy();
+		document.body.innerHTML = '';
 	});
 
 	it('does not call beforeFormSubmit for ignored forms', async () => {
@@ -79,6 +88,52 @@ describe('SwupFormsPlugin', () => {
 		expect(spy).toHaveBeenCalledWith(expect.objectContaining({ submitter }));
 	});
 
+	it('calls beforeFormSubmit for an externally associated submit button', async () => {
+		const spy = vitest.spyOn(plugin, 'beforeFormSubmit').mockImplementation(() => {});
+		swup.use(plugin);
+
+		const form = createForm('<form id="ext-form" action="/path" data-swup-form></form>');
+		const submitter = appendToBody<HTMLButtonElement>('<button type="submit" form="ext-form"></button>');
+		submitForm(form, submitter);
+
+		expect(spy).toHaveBeenCalledWith(expect.objectContaining({ delegateTarget: form, submitter }));
+	});
+
+	it('navigates to the formaction of an externally associated submitter', async () => {
+		swup.use(plugin);
+
+		const navigateSpy = vitest.spyOn(swup, 'navigate').mockImplementation(() => {});
+
+		const form = createForm('<form id="ext-form" action="/path" data-swup-form></form>');
+		const submitter = appendToBody<HTMLButtonElement>(
+			'<button type="submit" form="ext-form" formaction="/other"></button>'
+		);
+		submitForm(form, submitter);
+
+		expect(navigateSpy).toHaveBeenCalledWith(
+			'http://localhost:3000/other',
+			expect.objectContaining({ method: 'GET', cache: { read: false, write: true } }),
+			expect.objectContaining({ el: form })
+		);
+	});
+
+	it('includes externally associated inputs when navigating', async () => {
+		swup.use(plugin);
+
+		const navigateSpy = vitest.spyOn(swup, 'navigate').mockImplementation(() => {});
+
+		const form = createForm('<form id="ext-form" action="/path" data-swup-form></form>');
+		appendToBody('<input type="hidden" name="a" value="b" form="ext-form">');
+		const submitter = appendToBody<HTMLButtonElement>('<button type="submit" form="ext-form"></button>');
+		submitForm(form, submitter);
+
+		expect(navigateSpy).toHaveBeenCalledWith(
+			'http://localhost:3000/path?a=b',
+			expect.objectContaining({ method: 'GET' }),
+			expect.objectContaining({ el: form })
+		);
+	});
+
 	it('calls the form:submit hook', async () => {
 		swup.use(plugin);