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46 lines
2.2 KiB
Markdown
46 lines
2.2 KiB
Markdown
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# Authoring Script Ports
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Ports can expose functions for other ports to consume during their build. For
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example, the `vcpkg-cmake` helper port exposes the `vcpkg_cmake_configure()`
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helper function. Packaging common scripts into a shared helper port makes
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maintenance easier because all consumers can be updated from a single place.
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Because the scripts come from a port, they can be versioned and depended upon
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via all the same mechanisms as any other port.
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Script ports are implemented via the `vcpkg-port-config.cmake` extension
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mechanism. Before invoking the `portfile.cmake` of a port, vcpkg will first
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import `share/<port>/vcpkg-port-config.cmake` from each direct dependency. If
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the direct dependency is a host dependency, the import will be performed in the
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host installed tree (e.g.
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`${HOST_INSTALLED_DIR}/share/<port>/vcpkg-port-config.cmake`).
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Only direct dependencies are considered for `vcpkg-port-config.cmake` inclusion.
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This means that if a script port relies on another script port, it must
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explicitly import the `vcpkg-port-config.cmake` of its dependency.
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Script-to-script dependencies should not be marked as host. The dependency from
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a target port to a script should be marked host, which means that scripts should
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always already be natively compiling. By making script-to-script dependencies
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`"host": false`, it ensures that one script can depend upon the other being in
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its same install directory.
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Ports should never provide a `vcpkg-port-config.cmake` file under a different
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`share/` subdirectory than the current port (`${PORT}`).
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## Example
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```cmake
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# ${CURRENT_PACKAGES_DIR}/share/my-helper/vcpkg-port-config.cmake
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# This include guard ensures the file will be loaded only once
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include_guard(GLOBAL)
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# This is how you could pull in a transitive dependency
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include("${CMAKE_CURRENT_LIST_DIR}/../my-other-helper/vcpkg-port-config.cmake")
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# Finally, it is convention to put each public function into a separate file with a matching name
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include("${CMAKE_CURRENT_LIST_DIR}/my_helper_function_01.cmake")
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include("${CMAKE_CURRENT_LIST_DIR}/my_helper_function_02.cmake")
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include("${CMAKE_CURRENT_LIST_DIR}/my_helper_function_03.cmake")
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```
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