fix: keep if/elsif/else chains whole when filters are saved on the phone

src/lib/sieve/__tests__/external-rules.test.ts

@@ -253,6 +253,58 @@ describe('external rule preservation (issue #201)', () => {
     });
   });
 
+  // elsif and else were taken for statements of their own and cut at the
+  // first ";" in their body: a save wrote the chain back without its closing
+  // brace and without the comments after it, and the server refused it.
+  describe('if blocks with elsif and else', () => {
+    const read = (file: string) =>
+      readFileSync(join(__dirname, 'fixtures', file), 'utf-8').replace(/\r\n/g, '\n');
+    const resave = (script: string) => {
+      const parsed = parseScript(script);
+      return generateScript(parsed.rules, parsed.vacation, {
+        externalRequires: parsed.externalRequires,
+        extensions: ['fileinto', 'copy', 'imap4flags', 'mailbox', 'mailboxid'],
+      });
+    };
+
+    it('keeps a hand-written if/elsif/else chain whole', () => {
+      const fixture = read('hand-written-elsif.sieve');
+      const parsed = parseScript(fixture);
+      expect(parsed.isOpaque).toBe(false);
+      expect(parsed.rules).toHaveLength(1);
+      expect(parsed.rules[0].origin).toBe('opaque');
+      expect(parsed.rules[0].name).toBe('Sorted by hand');
+
+      const saved = resave(fixture);
+      expect(saved).toContain(fixture.slice(fixture.indexOf('# Sorted by hand')).trim());
+      expect(resave(saved)).toBe(saved);
+    });
+
+    it('keeps the category tabs section with its END marker', () => {
+      const fixture = read('category-tabs.sieve');
+      const parsed = parseScript(fixture);
+      expect(parsed.rules.filter((r) => !r.origin)).toHaveLength(4);
+      const external = parsed.rules.filter((r) => r.origin);
+      expect(external).toHaveLength(1);
+      expect(external[0].origin).toBe('opaque');
+
+      const section = fixture.slice(fixture.indexOf('# BEGIN category-tabs')).trim();
+      expect(external[0].rawBlock!.trim()).toBe(section);
+      const saved = resave(fixture);
+      expect(saved).toContain(section);
+      expect(saved.trimEnd().endsWith('# END category-tabs')).toBe(true);
+      expect(resave(saved)).toBe(saved);
+    });
+
+    it('still reads a lone if as a rule', () => {
+      const parsed = parseScript('require ["fileinto"];\nif header :contains "from" "a@example.org" {\n    fileinto "A";\n}\n# trailing note\n');
+      expect(parsed.rules).toHaveLength(1);
+      expect(parsed.rules[0].origin).toBe('external');
+      expect(parsed.rules[0].actions).toEqual([{ type: 'move', value: 'A' }]);
+      expect(parsed.rules[0].rawBlock).toContain('# trailing note');
+    });
+  });
+
   describe('round-trip', () => {
     it('preserves external rules through parse → generate → parse', () => {
       const initial = `require ["fileinto", "imap4flags"];\n\n# rule:[VIP]\nif header :contains "From" "boss@company.com" {\n    fileinto "VIP";\n    addflag "\\\\Flagged";\n}\n\n# Nextcloud Mail - begin\nif header :contains "Subject" "invoice" {\n    fileinto "Finance";\n}\n# Nextcloud Mail - end\n`;

src/lib/sieve/__tests__/fixtures/category-tabs.sieve

@@ -0,0 +1,41 @@
+/* @metadata:begin
+{"version":1,"rules":[{"id":"invoices","name":"Invoices","enabled":true,"matchType":"all","conditions":[{"field":"subject","comparator":"contains","value":["invoice","Rechnung"]}],"actions":[{"type":"move","value":"Finance/Invoices","mailboxId":"m12"},{"type":"star"},{"type":"add_label","value":"finance"}],"stopProcessing":false},{"id":"backup","name":"Backup","enabled":true,"matchType":"all","conditions":[{"field":"from","comparator":"contains","value":"news@example.com"}],"actions":[{"type":"copy","value":"Archive","mailboxId":"m7"}],"stopProcessing":false},{"id":"legacy","name":"Legacy path","enabled":true,"matchType":"all","conditions":[{"field":"from","comparator":"contains","value":"news@example.com"}],"actions":[{"type":"move","value":"Old/Path"}],"stopProcessing":false},{"id":"fwd","name":"Forward","enabled":true,"matchType":"all","conditions":[{"field":"from","comparator":"contains","value":"news@example.com"}],"actions":[{"type":"forward","value":"me@elsewhere.example","keepCopy":true}],"stopProcessing":false}]}
+@metadata:end */
+
+require ["copy", "fileinto", "imap4flags", "mailbox", "mailboxid"];
+
+# Rule: Invoices
+if header :contains "Subject" ["invoice", "Rechnung"] {
+    addflag "\\Flagged";
+    addflag "$label:finance";
+    fileinto :mailboxid "m12" "Finance/Invoices";
+}
+
+# Rule: Backup
+if header :contains "From" "news@example.com" {
+    fileinto :copy :mailboxid "m7" "Archive";
+}
+
+# Rule: Legacy path
+if header :contains "From" "news@example.com" {
+    fileinto "Old/Path";
+}
+
+# Rule: Forward
+if header :contains "From" "news@example.com" {
+    redirect :copy "me@elsewhere.example";
+}
+
+# BEGIN category-tabs (managed by the Inbox Category Tabs plugin)
+if header :contains "from" ["friend@example.org"] { }
+elsif header :contains "from" ["shop@example.com", "deals@example.net"] {
+    setflag "$category-promotions";
+}
+elsif anyof (
+    header :contains "subject" ["newsletter"],
+    exists "list-unsubscribe",
+    header :contains "precedence" ["bulk", "list"]
+) {
+    setflag "$category-updates";
+}
+# END category-tabs

src/lib/sieve/__tests__/fixtures/hand-written-elsif.sieve

@@ -0,0 +1,15 @@
+require ["fileinto", "imap4flags"];
+
+# Sorted by hand
+if header :contains "from" "boss@example.org" {
+    addflag "\\Flagged";
+    fileinto "Work";
+} elsif header :contains "list-id" "lists.example.org" {
+    fileinto "Lists";
+}
+# Everything else stays in the inbox
+else {
+    keep;
+}
+
+# end of my rules

src/lib/sieve/parser.ts

@@ -206,9 +206,21 @@ function skipIfStatement(s: string, i: number): number {
   return skipBalanced(s, i, '{', '}');
 }
 
+// Past whitespace and comments, to the next token.
+function skipSpaceAndComments(s: string, i: number): number {
+  while (i < s.length) {
+    if (/\s/.test(s[i])) { i++; continue; }
+    if (s[i] === '#') { i = skipHashComment(s, i); continue; }
+    if (s[i] === '/' && s[i + 1] === '*') { i = skipBlockComment(s, i); continue; }
+    break;
+  }
+  return i;
+}
+
 interface TopBlock {
   kind: 'require' | 'if' | 'vacation' | 'other';
   raw: string;          // from start-of-leading-text to end of statement
+  leading: string;      // the comments and whitespace in front of the statement
   statement: string;    // the statement itself (no leading comments/whitespace)
   startIdx: number;
   endIdx: number;
@@ -223,6 +235,7 @@ function scanTopLevel(content: string): TopBlock[] {
     blocks.push({
       kind,
       raw: content.slice(segmentStart, stmtEnd),
+      leading: content.slice(segmentStart, stmtStart),
       statement: content.slice(stmtStart, stmtEnd),
       startIdx: segmentStart,
       endIdx: stmtEnd,
@@ -254,6 +267,15 @@ function scanTopLevel(content: string): TopBlock[] {
       consume('require', stmtStart, i);
     } else if (ident === 'if') {
       i = skipIfStatement(content, i);
+      // elsif and else belong to the if in front of them. Taken as
+      // statements of their own they were cut at the first ";" in their
+      // body, and a save wrote back a block without its closing brace.
+      for (;;) {
+        const next = skipSpaceAndComments(content, i);
+        const branch = /^(elsif|else)(?![a-zA-Z0-9_])/.exec(content.slice(next, next + 6));
+        if (!branch) break;
+        i = skipIfStatement(content, next + branch[1].length);
+      }
       consume('if', stmtStart, i);
     } else if (ident === 'vacation') {
       i = skipStatement(content, i);
@@ -264,6 +286,15 @@ function scanTopLevel(content: string): TopBlock[] {
     }
   }
 
+  // Comments after the last statement, such as the "# END category-tabs"
+  // marker a plugin closes its section with, go with that statement, or a
+  // save would drop them.
+  const last = blocks[blocks.length - 1];
+  if (last && content.slice(segmentStart).trim() !== '') {
+    last.raw += content.slice(segmentStart);
+    last.endIdx = content.length;
+  }
+
   return blocks;
 }
 
@@ -632,6 +663,8 @@ function parseIfBlockToRule(block: TopBlock, idPrefix: string, index: number): F
   // statement always terminates at the matching `}`.
   const lastBraceIdx = afterIf.length - 1;
   if (braceIdx === -1 || afterIf[lastBraceIdx] !== '}' || lastBraceIdx < braceIdx) return null;
+  // An if with elsif or else branches stays as written.
+  if (skipBalanced(afterIf, braceIdx, '{', '}') !== afterIf.length) return null;
 
   const condStr = afterIf.slice(0, braceIdx).trim();
   const bodyStr = afterIf.slice(braceIdx + 1, lastBraceIdx).trim();
@@ -657,7 +690,7 @@ function parseIfBlockToRule(block: TopBlock, idPrefix: string, index: number): F
     }
   }
 
-  const leading = block.raw.slice(0, block.statement ? block.raw.length - block.statement.length : 0);
+  const leading = block.leading;
   const originLabel = detectOriginLabel(leading);
   const name = extractName(leading, `Rule ${index + 1}`);
 
@@ -676,7 +709,7 @@ function parseIfBlockToRule(block: TopBlock, idPrefix: string, index: number): F
 }
 
 function makeOpaqueRule(block: TopBlock, idPrefix: string, index: number): FilterRule {
-  const leading = block.raw.slice(0, block.raw.length - block.statement.length);
+  const leading = block.leading;
   const originLabel = detectOriginLabel(leading);
   const name = extractName(leading, `External rule ${index + 1}`);
   return {