Pranjal Raihan

This commit **improves the documentation for Whisker** within the `thrift` project by providing more comprehensive details. Specifically, it enhances the `thrift/doc/contributions/whisker.md` file with information on **variable qualifiers**, **strict rendering modes**, and **truthiness coercion**. This **documentation update** clarifies key aspects of Whisker's behavior, making it easier for developers to understand and correctly utilize these features. The change ensures a more accurate and complete reference for anyone working with Whisker templates.

This commit provides **documentation fixes and improvements** for the **Whisker templating language**. It specifically updates `thrift/doc/contributions/whisker.md` to add notes about Mustache-compatible sections and pragma statements. The changes also clarify existing grammar definitions and update the description for the `string.len` function. This **maintenance work** enhances the clarity and completeness of the **Whisker documentation**, making it easier for developers to understand and use its templating features.

This commit performs a comprehensive **documentation cleanup and minor code refinement** across various internal modules of the **Thrift compiler's Whisker component**. It **improves clarity, corrects typos, and expands explanations** for critical elements such as `polymorphic_native_handle`, `managed_ptr` lifetime semantics, `mstch_object` relationships, and `render_options::src_resolver`. Additionally, a `private` specifier was added to `native_function::context` and an unused macro undefinition was removed, contributing to **code hygiene**. This **refactoring effort** significantly enhances the **maintainability and developer understanding** of Whisker's internal workings without altering its external behavior.

This commit introduces a **new helper function**, `fromSerializable`, within the **Thrift C++2 dynamic type system**'s `TypeSystemBuilder`. This function provides a convenient way to **create a `TypeSystem` directly from a `SerializableTypeSystem`**, streamlining a common conversion operation. The change includes the function's implementation in `TypeSystemBuilder.cpp`, its declaration and detailed documentation in `TypeSystemBuilder.h`, and comprehensive **new test cases** in `TypeSystemTest.cpp` to ensure its reliability. This **new feature** improves the usability of the **dynamic type system** by simplifying a frequent task for developers.

This commit **refactors** the **Thrift definitions** by **removing terse write specifications** from the `type_system.thrift` file. This **maintenance** task standardizes the serialization behavior and improves the clarity of type definitions within the **type system module**. The change ensures consistent Thrift interface generation and consumption, impacting any components that rely on the `type_system.thrift` schema.

This commit introduces a **new capability** to the **Thrift dynamic type system** by adding a `buildDerivedFrom()` method to `TypeSystemBuilder`. This method allows creating a new `TypeSystem` that **overlays additional type definitions on top of an existing base TypeSystem**, handling conflict detection and delegation within the `thrift/lib/cpp2/dynamic` module. This enhancement is crucial for enabling **dynamic type definitions within TXL compilation**, which is a requirement for `EventRouter`'s usage of TXL. Comprehensive unit tests have been added to validate this new derivation functionality, covering various scenarios including base type resolution and conflict handling.

This commit **fixes the formatting of a multi-line comment** within the `thrift/lib/cpp2/server/RequestsRegistry.h` file. Specifically, it corrects the presentation of a comment block that describes the memory layout of the `RequestsRegistry` component. This is a **documentation maintenance** task, improving the readability and clarity of the **Thrift C++2 server library**'s internal documentation. The change has no functional impact but enhances developer understanding of the server's memory management.

This commit **adds comprehensive documentation** to the `DynamicValue` class within the **Thrift C++2 dynamic library**. The new documentation for `thrift/lib/cpp2/dynamic/DynamicValue.h` details the class's purpose, properties, and hierarchy, along with comparisons to other relevant APIs. This **documentation improvement** enhances developer understanding of `DynamicValue`, drawing insights from internal design discussions and existing detailed documentation like `TypeSystem.h`. The added context and clarity will aid in correct usage and integration of this core dynamic type.

This commit introduces **ergonomic `asRef()` helper methods** within the **Thrift C++2 schema `SyntaxGraph`** component, simplifying the creation of `TypeRef` objects from various schema node types. This **new capability** enhances developer experience by providing a more convenient and consistent way to obtain type references, mirroring existing functionality in `TypeSystem`. Additionally, `DefinitionNode` gains `isType()` and `asTypeRef()` methods for improved type introspection. The change primarily impacts code interacting with the `SyntaxGraph` for schema analysis, with existing tests updated to utilize these new helpers.

This commit **enhances error message clarity and safety** within the **Thrift C++2 schema generation** component. It specifically updates the `lookUpDefinition` and `lazyResolve` functions in `thrift/lib/cpp2/schema/SyntaxGraph.cpp` to utilize `folly::cEscape` when formatting definition keys in error messages. This **maintenance follow-up** ensures that special characters in definition keys are properly escaped, preventing potential issues and making error output more readable. The change improves the robustness of the **Thrift schema compiler** by providing consistently formatted and safer error reporting.

This commit **improves developer experience** by enhancing the **error reporting** within the **Thrift C++2 schema resolver**. Previously, the error message for **unresolved definitions** in `thrift/lib/cpp2/schema/detail/SchemaBackedResolver.cpp` contained unprintable characters, making it difficult to debug issues related to `SyntaxGraph` via `DebugProtocol`. This **bug fix** modifies the `SchemaIndex::resolve` function to **escape these unprintable characters**, ensuring the output is always readable. Consequently, developers will now receive clearer and more actionable error messages when diagnosing problems with `schema.thrift` definitions.

This commit performs **documentation cleanup** by **removing** the outdated `cpp2.md` file from the project. This **maintenance** task addresses the irrelevance of the document, which no longer contained pertinent information. By eliminating obsolete content, this change improves the accuracy and currency of the project's **C++ documentation**, ensuring users are not presented with misleading or irrelevant information.

This commit **fixes a critical bug** in **Thrift C++ service handler generation** where `ServiceHandler::getServiceSchema` failed to include omnibus schema data, resulting in an incomplete schema and invalid `SyntaxGraph`. It introduces a new **schema bundling capability** via `loadBundledSchema` in `thrift/lib/cpp2/schema/detail/Merge`, which correctly merges bundled schemas, including the omnibus schema. The `handlers_cpp.mustache` template is updated to leverage this function, ensuring that all generated **Thrift C++ service handlers** provide a complete and accurate schema. This change significantly improves the reliability of **Thrift schema reflection and introspection** for services utilizing omnibus types.

This commit **refactors** the **Thrift C++2 dynamic type system** by systematically replacing all occurrences of `folly::throw_exception` with standard C++ `throw` statements. This **maintenance** change is performed because exceptions are always enabled in this environment, making the `folly` compatibility helper redundant. The affected modules include `SerializableRecord`, `TypeSystem`, and `SerializableTypeSystemBuilder` within `thrift/lib/cpp2/dynamic`. This **simplifies the codebase**, removes unnecessary `folly/lang/Exception.h` includes, and has no functional impact on the system's behavior.

This commit primarily introduces a significant **refactoring** within the **`thrift/lib/cpp2/dynamic`** module, specifically for `PrimitiveDatum` and `SerializableRecord`, by adopting **C++20 concepts** for more robust template constraints and leveraging synthesized comparison operators. Concurrently, it delivers a crucial **bug fix** in the **`thrift/lib/cpp2/schema`** module, addressing a type casting error within `toTypeSystemAnnotation`. This fix corrects the casting of `Primitive::I64` from `int8_t` to `int64_t`, thereby preventing potential **data loss** during schema annotation processing. The changes enhance code modernity and type safety while resolving a critical data integrity issue.

This commit **modernizes** the project's C++ codebase by adopting **C++20 features**, leveraging new language constructs and standard library components. This **maintenance** effort aims to improve code quality, potentially enhance performance, and align the project with contemporary C++ development practices. The update broadly affects **all C++ components**, requiring a C++20-compliant compiler for future development and compilation.

This commit performs a significant **refactoring** of the **Thrift C++2 dynamic type system hierarchy** by **merging `SourceIndexedTypeSystem` directly into `TypeSystem`**. This change integrates source information lookup methods, such as `getUserDefinedTypeBySourceIdentifier` and `getUserDefinedTypesAtLocation`, directly into the base `TypeSystem` interface, eliminating the need for a separate `SourceIndexedTypeSystem`. Consequently, components like `TypeSystemBuilder`, `SerializableTypeSystemBuilder`, `SchemaRegistry`, and `SyntaxGraph` are updated to use the unified `TypeSystem`, simplifying API usage and assuming best-effort source information is always available. This **simplification** streamlines the internal representation and external interaction with Thrift's dynamic type systems.

This commit introduces a **new capability** to the **Folly library** by adding the `current_exception_wrapper` helper function in `folly/ExceptionWrapper.h`. This function simplifies the process of creating an `exception_wrapper` object from the currently active exception. It aims to streamline error handling and exception capture patterns, making it more convenient to manage exceptions within the codebase.

This commit introduces an **enhancement** to the **Thrift schema processing** within `SyntaxGraph`, specifically in the `TypeSystemFacade`, to convert `AnyStruct` references to the built-in `Any` type during `TypeSystem` construction. This **new capability** leverages the `TypeSystem`'s first-class support for `Any`, streamlining type representation and simplifying subsequent type resolution within the schema graph. Although `AnyStruct` may still exist as a `StructNode` for lookup, all `TypeRef`s will now consistently point to the built-in `Any`. This ensures earlier and more consistent type handling, with a new test case in `thrift/lib/cpp2/schema/test/SyntaxGraphTest.cpp` validating the conversion.

This commit **enhances the Thrift C++2 protocol mapping system** by introducing **bidirectional conversion capabilities** for `StandardProtocol` enum values. It **extends the existing `get_standard_protocol` functionality** to encompass all standard protocols and, critically, adds new type aliases like `protocolReaderFor` and `protocolWriterFor` to map the enum back to concrete reader and writer types. This **new feature** refactors the underlying mapping logic in `thrift/lib/cpp2/protocol` using `consteval` functions, improving type safety and programmatic interaction with different protocol implementations. New tests validate these expanded mappings, ensuring robust handling of protocol conversions.