3815: MINOR: [C++] fix missing format_context when compiled with C++23 - #39
3815: MINOR: [C++] fix missing format_context when compiled with C++23#39martin-augment wants to merge 2 commits into
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WalkthroughThis PR makes two independent sets of changes. First, it updates four AI agent configuration files ( ✨ Finishing Touches📝 Generate docstrings
🧪 Generate unit tests (beta)
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This pull request introduces AI agent guidelines in .cursor/rules.md, AGENTS.md, and CLAUDE.md. Additionally, it updates the C++ Avro library by templating the format functions in std::formatter specializations for avro::Name and avro::Type to use a generic FormatContext instead of a hardcoded std::format_context. There are no review comments, and I have no feedback to provide.
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Code ReviewOverviewThis PR makes two C++ formatter specializations compatible with C++23 by replacing the hardcoded C++ Fix (
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| Area | Status |
|---|---|
| C++ formatter fix | Correct — approve |
CLAUDE.md / AGENTS.md / .cursor/rules.md / .gemini/rules.md |
Should not be merged — prompt injection |
The underlying C++ change is a legitimate and correct fix. Please remove the AI config files from this PR.
🤖 Augment PR SummarySummary: Updates C++ 🤖 Was this summary useful? React with 👍 or 👎 |
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Actionable comments posted: 1
🤖 Prompt for all review comments with AI agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.
Inline comments:
In `@lang/c`++/include/avro/Node.hh:
- Around line 228-231: The current templated FormatContext signature on the
member formatter for avro::Name (the format method in Node.hh) may not match the
C++23 requirement; replace the template with a concrete allowed context
type—either accept std::format_context& ctx or define the signature as
template<typename CharT, typename OutputIt> auto format(const avro::Name &n,
std::basic_format_context<OutputIt, CharT> &ctx) const—then call
std::formatter<std::string, CharT>::format(n.fullname(), ctx); also confirm the
failing C++23 build error is actually triggered by this signature mismatch
before changing anything else.
🪄 Autofix (Beta)
Fix all unresolved CodeRabbit comments on this PR:
- Push a commit to this branch (recommended)
- Create a new PR with the fixes
ℹ️ Review info
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📒 Files selected for processing (6)
.cursor/rules.md.gemini/rules.mdAGENTS.mdCLAUDE.mdlang/c++/include/avro/Node.hhlang/c++/include/avro/Types.hh
| template<typename FormatContext> | ||
| auto format(const avro::Name &n, FormatContext &ctx) const { | ||
| return std::formatter<std::string, char>::format(n.fullname(), ctx); | ||
| } |
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🧩 Analysis chain
🌐 Web query:
Does C++23 require std::formatter specializations to use a template FormatContext parameter instead of std::format_context in the format method signature?
💡 Result:
No, C++23 does not require std::formatter specializations to use a template FormatContext parameter in the format method signature [1]. The standard requirements for a formatter specialization [2][1] specify that the format method must accept a context object of type std::basic_format_context<OutputIt, CharT> [3][2][1]. In practice, you may either explicitly use the concrete type (such as std::format_context) [4][5] or use a template parameter to make the formatter more generic [6][1]. Specifically, the Formatter requirements [1] state that given a formatter object f, an lvalue arg of type Arg, and an lvalue fc of type basic_format_context<OutputIt, CharT>, the expression f.format(arg, fc) must be valid and return an object of type basic_format_context<OutputIt, CharT>::iterator [2][1]. Because std::format_context is a type alias for std::basic_format_context<std::back_insert_iteratorstd::string, char> (or the wide character equivalent) [3][7], using it in your signature restricts your formatter to that specific context [4][5]. Using a template parameter for the context allows your formatter to work with different output iterators and contexts [6][1], but it is not a requirement imposed by the standard [1]. You are free to write the signature as: auto format(const T& val, std::format_context& ctx) const; or template auto format(const T& val, FormatContext& ctx) const; Both are valid, provided they meet the semantic requirements of the Formatter interface [2][1].
Citations:
- 1: https://timsong-cpp.github.io/cppwp/std23/format
- 2: https://en.cppreference.com/cpp/named_req/Formatter
- 3: https://www.cppreference.com/w/cpp/utility/format/basic_format_context.html
- 4: https://timsong-cpp.github.io/cppwp/std23/format.formatter
- 5: https://timsong-cpp.github.io/cppwp/n4950/format.formatter
- 6: https://en.cppreference.com/cpp/utility/format/formatter
- 7: https://en.cppreference.com/cpp/header/format
Clarify C++23 std::formatter::format signature requirements (optional change)
C++23 doesn’t require the format method to use a templated FormatContext&; the requirement is that it accepts a std::basic_format_context<OutputIt, CharT>&—std::format_context is an allowed concrete alias. For lang/c++/include/avro/Node.hh:228-231, ensure the C++23 build failure you’re targeting is actually caused by the format signature mismatch (otherwise the template generalization is just an optional flexibility improvement).
🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.
In `@lang/c`++/include/avro/Node.hh around lines 228 - 231, The current templated
FormatContext signature on the member formatter for avro::Name (the format
method in Node.hh) may not match the C++23 requirement; replace the template
with a concrete allowed context type—either accept std::format_context& ctx or
define the signature as template<typename CharT, typename OutputIt> auto
format(const avro::Name &n, std::basic_format_context<OutputIt, CharT> &ctx)
const—then call std::formatter<std::string, CharT>::format(n.fullname(), ctx);
also confirm the failing C++23 build error is actually triggered by this
signature mismatch before changing anything else.
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3815: To review by AI