[PATCH v2] libcamera: yaml_parser: Make default value templated in `get()`

[Kieran Bingham]

Quoting Barnabás Pőcze (2024-06-12 23:46:16)
> This way the construction of the default value of type `T`
> can be delayed until it is really needed, which is useful,
> for example when `T == std::string` and the default value comes
> from a string literal, as the default value string would always
> be constructed otherwise, even if not needed.
> 
> Signed-off-by: Barnabás Pőcze <pobrn at protonmail.com>
> ---
> Changes in v2:
>  * update documentation

Thanks - fully green:
 - https://gitlab.freedesktop.org/camera/libcamera/-/pipelines/1199993

I had already provided a tag for this on v1, so I think it still holds:

Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
 
> ---
>  include/libcamera/internal/yaml_parser.h | 6 +++---
>  src/libcamera/yaml_parser.cpp            | 2 +-
>  2 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/include/libcamera/internal/yaml_parser.h b/include/libcamera/internal/yaml_parser.h
> index b6979d73..3ac27e06 100644
> --- a/include/libcamera/internal/yaml_parser.h
> +++ b/include/libcamera/internal/yaml_parser.h
> @@ -179,10 +179,10 @@ public:
>  #endif
>         std::optional<T> get() const;
> 
> -       template<typename T>
> -       T get(const T &defaultValue) const
> +       template<typename T, typename U>
> +       T get(U &&defaultValue) const
>         {
> -               return get<T>().value_or(defaultValue);
> +               return get<T>().value_or(std::forward<U>(defaultValue));
>         }
> 
>  #ifndef __DOXYGEN__
> diff --git a/src/libcamera/yaml_parser.cpp b/src/libcamera/yaml_parser.cpp
> index aac9a2bd..b68a44c1 100644
> --- a/src/libcamera/yaml_parser.cpp
> +++ b/src/libcamera/yaml_parser.cpp
> @@ -104,7 +104,7 @@ std::size_t YamlObject::size() const
>   */
> 
>  /**
> - * \fn template<typename T> YamlObject::get<T>(const T &defaultValue) const
> + * \fn template<typename T, typename U> YamlObject::get<T>(U &&defaultValue) const
>   * \brief Parse the YamlObject as a \a T value
>   * \param[in] defaultValue The default value when failing to parse
>   *
> --
> 2.45.2
>