Enhance prompt template formatting: support nested placeholders and unpaired braces handling

[dcstrange]

以下是针对你提出的所有代码修改的完整 Git 提交说明，包含中英文版本。

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提交说明（中文）

标题

增强模板格式化功能，支持嵌套结构占位符与未成对花括号处理

详细描述

1. 新增功能：

   • 支持嵌套结构占位符（如 {data[key]} 和 {obj.attr}），这些占位符将被保留原样，不被 str.format() 解析。
   • 引入未成对花括号的处理逻辑：
     • 未闭合的 { 转换为普通字符 {{。
     • 单独的 } 转换为普通字符 }}。
     • 确保未成对的花括号不会触发解析错误。

2. 修复问题：

   • 修复嵌套结构占位符在模板中被错误解析的问题。
   • 修复未成对花括号导致 str.format() 抛出异常的问题。

3. 具体修改：

   • 新增 _replace_unpaired_braces 方法，使用正则表达式检测未成对的 { 或 }，并将其替换为普通字符，确保模板完整性。
   • 修改 SafeFormatter.format 方法，调用 _replace_unpaired_braces 预处理模板，避免未成对花括号干扰格式化流程。
   • 优化嵌套结构的正则匹配逻辑，将匹配到的嵌套占位符（如 {data[key]}）转义为普通文本 {{data[key]}}，避免解析。

4. 测试覆盖：

   • 测试未成对的 { 和 }：
     • {abc -> {abc（被保留为普通字符）。
     • abc} -> abc}（被保留为普通字符）。
   • 测试嵌套占位符：
     • {data[key]} -> 被保留原样。
   • 测试合法占位符的正常解析：
     • {name} -> 被替换为传入的数据值。
   • 测试混合场景：
     • {abc}def} -> {abc}def}。
     • Hello {name}, Welcome {place}! -> Hello Alice, Welcome Wonderland!（假设传入数据）。

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提交说明（英文）

Title

Enhance template formatting: support nested placeholders and unpaired braces handling

Description

1. New Features:

   • Added support for nested placeholders (e.g., {data[key]} and {obj.attr}), which are preserved as plain text and will not be parsed by str.format().
   • Introduced handling for unpaired curly braces:
     • Unclosed { is converted to a plain character {{.
     • Lone } is converted to a plain character }}.
     • Ensures unpaired braces do not cause parsing errors.

2. Bug Fixes:

   • Fixed an issue where nested placeholders were incorrectly parsed or caused errors.
   • Fixed an issue where unpaired curly braces triggered str.format() exceptions.

3. Changes:

   • Added _replace_unpaired_braces method, which uses regular expressions to detect unpaired { or } and replaces them with plain characters, maintaining template integrity.
   • Updated SafeFormatter.format to call _replace_unpaired_braces for pre-processing templates, preventing unpaired braces from interfering with formatting.
   • Improved regex logic for nested placeholders to escape them as plain text {{data[key]}}, avoiding unnecessary parsing.

4. Test Coverage:

   • Tested unpaired braces:
     • {abc -> {abc (retained as plain text).
     • abc} -> abc} (retained as plain text).
   • Tested nested placeholders:
     • {data[key]} -> preserved as is.
   • Tested valid placeholders for correct replacement:
     • {name} -> replaced with the value from input data.
   • Tested mixed scenarios:
     • {abc}def} -> {abc}def}.
     • Hello {name}, Welcome {place}! -> Hello Alice, Welcome Wonderland! (assuming input data provided).

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提交示例

标题：

增强模板格式化功能，支持嵌套结构占位符与未成对花括号处理 / Enhance template formatting: support nested placeholders and unpaired braces handling

详细描述：

添加了对未成对花括号的处理逻辑，确保未成对的 `{` 或 `}` 不再触发解析错误，而是被替换为普通字符。此外，支持嵌套结构占位符（如 `{data[key]}`），这些占位符将被保留原样而不解析。优化了模板格式化逻辑，增强了健壮性，并增加了全面的测试覆盖。

英文：

Added handling for unpaired curly braces to ensure that unpaired `{` or `}` no longer cause parsing errors but are instead replaced with plain characters. Additionally, added support for nested placeholders (e.g., `{data[key]}`), which are preserved as plain text without parsing. Improved template formatting logic, enhanced robustness, and added comprehensive test coverage.

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