fix: keep a hand-picked sender's own signature and swap it after typing under it

src/lib/__tests__/compose-screen-wiring.test.ts

@@ -0,0 +1,15 @@
+import { describe, expect, it } from 'vitest';
+import fs from 'node:fs';
+import path from 'node:path';
+
+// Composer behaviour that lives in ComposeScreen itself, checked on its
+// source (the suite has no React Native renderer).
+const source = fs.readFileSync(path.resolve(__dirname, '../../screens/ComposeScreen.tsx'), 'utf8');
+
+describe('ComposeScreen wiring', () => {
+  it('lets a From picked by hand bring its own (possibly empty) signature', () => {
+    expect(source).toMatch(/signatureIdentityFor\(primaryIdentity, identities, \{ pickedByUser: identityPickedByUser \}\)/);
+    const sheet = source.slice(source.indexOf('<IdentitySheet'));
+    expect(sheet.slice(0, 400)).toMatch(/onPick=\{\(identity\) => \{[^}]*setIdentityPickedByUser\(true\)/);
+  });
+});

src/lib/__tests__/signature-utils.test.ts

@@ -75,6 +75,20 @@ describe('embedded signature range', () => {
     expect(spliceSignature('<p>x</p>', a)).toBe(`<p>x</p>${a}`);
   });
 
+  it('swaps the signature after the user typed into the line under it, keeping the text', () => {
+    const a = buildEmbeddedSignatureHtml({ textSignature: 'A' }, { separator: true });
+    const b = buildEmbeddedSignatureHtml({ textSignature: 'B' }, { separator: true });
+    const typed = a.replace('data-signature-block="end"><br></p>', 'data-signature-block="end">PS: call me</p>');
+    expect(typed).not.toBe(a);
+    const body = `<p>hello</p>${typed}<div data-quoted-html="true">q</div>`;
+    expect(containsEmbeddedSignature(body)).toBe(true);
+    const swapped = spliceSignature(body, b);
+    expect(swapped).toBe(`<p>hello</p>${b}<p>PS: call me</p><div data-quoted-html="true">q</div>`);
+    // One signature, never two.
+    expect(swapped.match(/data-signature-block="body"/g)).toHaveLength(1);
+    expect(stripEmbeddedSignature(body)).toBe('<p>hello</p><p>PS: call me</p><div data-quoted-html="true">q</div>');
+  });
+
   it('inserts above the quote marker', () => {
     const sig = buildEmbeddedSignatureHtml({ textSignature: 'S' }, { separator: true });
     const marker = '<div data-quoted-html="true">';
@@ -93,6 +107,11 @@ describe('signatureIdentityFor', () => {
     expect(signatureIdentityFor(alias, [alias, primary, signedAlias])).toBe(primary);
   });
 
+  it("keeps a hand-picked identity's own empty signature", () => {
+    expect(signatureIdentityFor(alias, [alias, primary], { pickedByUser: true })).toBeNull();
+    expect(signatureIdentityFor(signedAlias, [alias, primary, signedAlias], { pickedByUser: true })).toBe(signedAlias);
+  });
+
   it('returns null when neither has one', () => {
     expect(signatureIdentityFor(alias, [alias, { id: 'p', mayDelete: false }])).toBeNull();
     expect(signatureIdentityFor(null, [primary])).toBeNull();

src/lib/signature-utils.ts

@@ -83,9 +83,14 @@ export function hasSignature(signature?: SignatureSource): boolean {
 export function signatureIdentityFor<T extends { textSignature?: string; htmlSignature?: string; mayDelete?: boolean }>(
   identity: T | null | undefined,
   identities: T[],
+  options: { pickedByUser?: boolean } = {},
 ): T | null {
   if (!identity) return null;
   if (hasSignature(identity)) return identity;
+  // An identity the user picked by hand keeps its own, also an empty one:
+  // switching to a team address without a signature sent the team mail with
+  // the personal signature (webmail email-composer.tsx ownSignatureIdentity).
+  if (options.pickedByUser) return null;
   const primary = identities.find((i) => !i.mayDelete) ?? identities[0];
   return primary && hasSignature(primary) ? primary : null;
 }
@@ -242,11 +247,28 @@ export function buildEmbeddedSignatureHtml(
   return '';
 }
 
+// The end marker is the empty line under the signature, so a tap below the
+// signature puts the caret there; its content (group 1) may be text the user
+// typed.
 const SIGNATURE_RANGE_RE = new RegExp(
-  `<p\\s+${SIGNATURE_RANGE_MARKER}=["'](?:separator|start)["'][^>]*>[\\s\\S]*?<p\\s+${SIGNATURE_RANGE_MARKER}=["']end["'][^>]*>(?:<br\\s*/?>)?</p>`,
+  `<p\\s+${SIGNATURE_RANGE_MARKER}=["'](?:separator|start)["'][^>]*>[\\s\\S]*?<p\\s+${SIGNATURE_RANGE_MARKER}=["']end["'][^>]*>((?:(?!</p>)[\\s\\S])*)</p>`,
   'i',
 );
 
+/**
+ * Text typed into the end marker is the user's, not part of the signature:
+ * kept as an ordinary paragraph after it (webmail compose-format.ts
+ * removeSignatureRange).
+ */
+function keptEndText(endContent: string): string {
+  const text = endContent
+    .replace(/<br\s*\/?>/gi, '')
+    .replace(/<[^>]*>/g, '')
+    .replace(/&nbsp;| /g, ' ')
+    .trim();
+  return text ? `<p>${endContent}</p>` : '';
+}
+
 /** True when the body carries an embedded signature range. */
 export function containsEmbeddedSignature(html: string): boolean {
   return SIGNATURE_RANGE_RE.test(html);
@@ -259,7 +281,7 @@ export function containsEmbeddedSignature(html: string): boolean {
  */
 export function spliceSignature(html: string, nextSignatureHtml: string): string {
   if (SIGNATURE_RANGE_RE.test(html)) {
-    return html.replace(SIGNATURE_RANGE_RE, () => nextSignatureHtml);
+    return html.replace(SIGNATURE_RANGE_RE, (_m, end: string) => `${nextSignatureHtml}${keptEndText(end)}`);
   }
   if (!nextSignatureHtml) return html;
   return `${html}${nextSignatureHtml}`;
@@ -267,7 +289,7 @@ export function spliceSignature(html: string, nextSignatureHtml: string): string
 
 /** The body without its embedded signature range. */
 export function stripEmbeddedSignature(html: string): string {
-  return html.replace(SIGNATURE_RANGE_RE, '');
+  return html.replace(SIGNATURE_RANGE_RE, (_m, end: string) => keptEndText(end));
 }
 
 /**

src/screens/ComposeScreen.tsx

@@ -985,10 +985,14 @@ export default function ComposeScreen({ route, navigation }: Props) {
     return identities.find((i) => i.id === selectedIdentityId) ?? defaultIdentity;
   }, [identities, selectedIdentityId]);
 
-  // An alias without a signature falls back to the primary identity's.
+  // Set once the user picks From by hand: their pick then brings its own
+  // signature, also when it has none (webmail identityPickedByUser).
+  const [identityPickedByUser, setIdentityPickedByUser] = React.useState(false);
+  // An alias without a signature falls back to the primary identity's,
+  // unless the user picked it.
   const signatureIdentity = React.useMemo(
-    () => signatureIdentityFor(primaryIdentity, identities),
-    [primaryIdentity, identities],
+    () => signatureIdentityFor(primaryIdentity, identities, { pickedByUser: identityPickedByUser }),
+    [primaryIdentity, identities, identityPickedByUser],
   );
 
   const openIdentityPicker = () => {
@@ -3220,7 +3224,7 @@ export default function ComposeScreen({ route, navigation }: Props) {
         onClose={() => setIdentitySheetOpen(false)}
         identities={identities}
         selectedIdentityId={selectedIdentityId}
-        onPick={(identity) => { setSelectedIdentityId(identity.id); setFromOverride(null); }}
+        onPick={(identity) => { setSelectedIdentityId(identity.id); setFromOverride(null); setIdentityPickedByUser(true); }}
       />
 
       <AttachmentPreviewModal {...filePreview.modalProps} />