fix: range with column-like sheet prefix in RHS

lib/lexers/canEndRange.ts

@@ -11,6 +11,9 @@ export function canEndRange (str: string, pos: number): boolean {
 }
 
 // partial: [A-Za-z0-9_($.]
+// Also rejects "!" — a ternary range must not end where a sheet prefix
+// begins (e.g. "F2:B" in "B!F2:B!F20" is not a ternary range; the
+// trailing "B" is the start of the second sheet prefix "B!").
 export function canEndPartialRange (str: string, pos: number): boolean {
   const c = str.charCodeAt(pos);
   return !(
@@ -20,6 +23,7 @@ export function canEndPartialRange (str: string, pos: number): boolean {
     (c === 95) || // _
     (c === 40) || // (
     (c === 36) || // $
-    (c === 46) // .
+    (c === 46) || // .
+    (c === 33) // !
   );
 }

lib/translateToA1.spec.ts

@@ -246,6 +246,24 @@ describe('translate works with trimmed ranges', () => {
   });
 });
 
+describe('quote sheet prefix on RHS of range operator', () => {
+  // Excel unconditionally quotes the sheet prefix on the right side of
+  // a range operator in XLSX: Sheet1!A1:Sheet1!B2 → Sheet1!A1:'Sheet1'!B2.
+  test('RHS sheet prefix is quoted unconditionally', () => {
+    isR2A('=B!R[-1]C[5]:B!R[17]C[5]', 'A2', "=B!F1:'B'!F19");
+    isR2A('=Sheet1!R1C1:Sheet1!R2C2', 'A1', "=Sheet1!$A$1:'Sheet1'!$B$2");
+  });
+
+  test('LHS sheet prefix is not quoted', () => {
+    isR2A('=B!R1C1', 'A1', '=B!$A$1');
+    isR2A('=Sheet1!R1C1', 'A1', '=Sheet1!$A$1');
+  });
+
+  test('already-quoted RHS prefix is not double-quoted', () => {
+    isR2A("='Sheet 1'!R1C1:'Sheet 1'!R2C2", 'A1', "='Sheet 1'!$A$1:'Sheet 1'!$B$2");
+  });
+});
+
 describe('translate r & c as LET parameters', () => {
   // Unlike in A1, LET(c,1,c) is not valid syntax with the R1C1 notation in Excel.
   // If you create a cell with this expression in A1 mode and flip to R1C1, Excel

lib/translateToA1.ts

@@ -7,6 +7,8 @@ import { parseA1Range } from './parseA1Range.ts';
 import type { RangeA1, ReferenceR1C1Xlsx, Token } from './types.ts';
 import { stringifyTokens } from './stringifyTokens.ts';
 import { cloneToken } from './cloneToken.ts';
+import { OPERATOR } from './constants.ts';
+import { quotePrefix } from './stringifyPrefix.ts';
 
 // Turn on the most permissive setting when parsing ranges so we don't have to think about
 // this option. We already know that range tokens are legal, so we're not going to encounter
@@ -164,6 +166,29 @@ export function translateTokensToA1 (
     outTokens[outTokens.length] = token;
   }
 
+  // Excel unconditionally quotes the sheet prefix on the RHS of a range
+  // operator in XLSX files: Sheet1!A1:Sheet1!B2 → Sheet1!A1:'Sheet1'!B2.
+  // Apply the same quoting to match Excel's serialization.
+  for (let i = 2; i < outTokens.length; i++) {
+    const tok = outTokens[i];
+    if (!isRange(tok)) {
+      continue;
+    }
+    const prev = outTokens[i - 1];
+    if (prev?.type !== OPERATOR || prev.value !== ':') {
+      continue;
+    }
+    const bangIdx = tok.value.indexOf('!');
+    if (bangIdx > 0) {
+      const prefix = tok.value.slice(0, bangIdx);
+      // Only quote if not already quoted
+      if (prefix[0] !== "'") {
+        outTokens[i] = cloneToken(tok);
+        outTokens[i].value = quotePrefix(prefix) + tok.value.slice(bangIdx);
+      }
+    }
+  }
+
   return outTokens;
 }
 

lib/translateToR1C1.spec.ts

@@ -154,6 +154,19 @@ describe('translate involved cases from A1 to RC', () => {
   });
 });
 
+describe('translate cross-sheet ranges', () => {
+  test('sheet prefix not consumed as ternary range end', () => {
+    // B!F2:B!F20 from B137 — the second B! is a sheet prefix, not a
+    // ternary range endpoint. Without the fix, the lexer with
+    // allowTernary:true parses "F2:B" as a ternary range, consuming
+    // the B from the second sheet prefix.
+    isA2R('=B!F2:B!F20', 'B137', '=B!R[-135]C[4]:B!R[-117]C[4]');
+    isA2R('=SUM(Sheet1!A1:Sheet1!A10)', 'C5', '=SUM(Sheet1!R[-4]C[-2]:Sheet1!R[5]C[-2])');
+    // Single-letter sheet names that look like column letters
+    isA2R('=X!D3:X!D10', 'A1', '=X!R[2]C[3]:X!R[9]C[3]');
+  });
+});
+
 describe('translate works with merged ranges', () => {
   test('preserves token metadata and locations', () => {
     // This tests that: