v0.1.3

- Fix retry buffer size calculation in AppendFormatInternal
- Add diagnostic info to FormatException

Author: xpTURN

CHANGELOG.md

@@ -2,45 +2,68 @@
 
 ---
 
+## [0.1.3] - 2026-02-26
+
+### Bug Fixes
+
+#### Fix retry buffer size calculation in AppendFormatInternal
+
+- Changed retry buffer from `written > buf.Length ? written : buf.Length * 2` to `buf.Length * 2`
+- `written` is unreliable on TryFormat failure (may be 0 or partial), so always double the buffer
+
+### Improvements
+
+#### Add diagnostic info to FormatException
+
+- FormatException message now includes `Type`, `alignment`, `format` for easier debugging
+
 ## [0.1.2] - 2026-02-26
 
 ### Performance Improvements
 
 #### Replace Composite Format with Direct TryFormatDelegate
+
 - Removed `AppendFormattedViaComposite`, replaced with `AppendFormatInternal`
 - Before: built composite format string (`"{0,alignment:format}"`) on the stack per call, then re-parsed via `_sb.AppendFormat`
 - After: calls `FormatterCache<T>.TryFormatDelegate` directly and handles alignment padding inline
 - Eliminates composite string construction and re-parsing overhead
 
 #### Avoid Boxing on Null Check (Debug build only)
+
 - Changed null check from `value == null` to `default(T) == null && value == null`
 - Prevents unnecessary boxing for value types (null branch entered only for reference types / Nullable)
 
 ### Tests
 
 #### Benchmark Test Improvements
+
 - `StringBuilder_FourArgs`: changed from reusing StringBuilder to creating a new instance per iteration (fair comparison)
 - `StringBuilder128_FourArgs`: added benchmark that creates a new StringBuilder with initial capacity 128 per iteration
 - `StringBuilderShare_FourArgs`: separated the existing shared-StringBuilder approach into its own benchmark
 
-
 ## [0.1.1] - 2026-02-24
 
 ### New Features
 
 #### Format Parameter Support
+
 Alignment and format specifiers are now properly supported.
+
 - Fixed: Alignment and format parameters were previously ignored
 - Example: `XString.Format($"Score: {score,10:F2}")` aligns to 10 characters with 2 decimal places
 
 #### Support for Up to 16 Format Arguments
+
 Format overloads extended from T1~T4 to T1~T16.
+
 - Example: `XString.Format("{0} {1} ... {15}", arg1, arg2, ..., arg16)`
 
 ### Tests
+
 Expanded from 34 to 93 (+174%)
 
 Added tests:
+
 - 4 concurrency tests (multithreading safety)
 - 11 edge case tests (boundary conditions, large strings)
 - 33 functional tests (various scenarios)

src/XString/Assets/XString/Runtime/XInterpolatedStringHandler.cs

@@ -225,9 +225,11 @@ private void AppendFormatInternal<T>(T value, int alignment, ReadOnlySpan<char>
             if (!FormatterCache<T>.TryFormatDelegate(value, buf, out var written, format))
             {
                 // Retry with larger heap-free buffer.
-                buf = stackalloc char[written > buf.Length ? written : buf.Length * 2];
+                buf = stackalloc char[buf.Length * 2];
                 if (!FormatterCache<T>.TryFormatDelegate(value, buf, out written, format))
-                    throw new FormatException("Failed to format value.");
+                {
+                    throw new FormatException($"Failed to format value. Type={typeof(T).Name}, alignment=0, format={format.ToString()}");
+                }
             }
             _sb.Append(buf.Slice(0, written));
             return;
@@ -241,9 +243,11 @@ private void AppendFormatInternal<T>(T value, int alignment, ReadOnlySpan<char>
             Span<char> buf = stackalloc char[typeof(T).IsValueType ? Unsafe.SizeOf<T>() * 8 : DefaultFormatBuffer];
             if (!FormatterCache<T>.TryFormatDelegate(value, buf, out var written, format))
             {
-                buf = stackalloc char[written > buf.Length ? written : buf.Length * 2];
+                buf = stackalloc char[buf.Length * 2];
                 if (!FormatterCache<T>.TryFormatDelegate(value, buf, out written, format))
-                    throw new FormatException("Failed to format value.");
+                {
+                    throw new FormatException($"Failed to format value. Type={typeof(T).Name}, alignment={alignment}, format={format.ToString()}");
+                }
             }
 
             int padding = width - written;

src/XString/Assets/XString/package.json

@@ -1,6 +1,6 @@
 {
   "name": "com.xpturn.xstring",
-  "version": "0.1.2",
+  "version": "0.1.3",
   "displayName": "xpTURN.XString",
   "description": "ZString API wrapper package for Unity. ZString does not provide a dedicated API for interpolated strings, so this package aims to provide `XString.Format($\"...\")` and format-string overloads.",
   "unity": "2022.3",