fix(cmake): find missing Python development components#6116
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If a parent project called find_package(Python) without the development components, pybind11 skipped its own find, so pybind11_add_module failed and pybind11::embed did not link to Python::Python. Ask FindPython for the missing components instead, keeping the interpreter already selected. Assisted-by: ClaudeCode:claude-opus-5 Claude-Session: https://claude.ai/code/session_013JABmnjt9oAh29p1pytAB3
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I think this is both helpful and there are issues with it. Will investigate. See #6112.
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Description
pybind11NewTools.cmakeskipped its Python discovery ifPython_FOUNDorPython3_FOUNDwas set. A parent project that didfind_package(Python COMPONENTS Interpreter)(frequently out of the user's control) thus left pybind11 without the development components, which caused:pybind11_add_moduleto fail withUnknown CMake command "python_add_library"ortarget Python::Module is not defined,pybind11::embedto silently miss the link toPython::Python.pybind11 now asks FindPython for the missing development components instead of skipping the find. It keeps the name (
PythonorPython3) and the interpreter that the parent project selected, and it makes the new targets global in submodule mode. If the parent project already supplied the development components, the behavior does not change.The
subdirectory_embedCMake build test now does a partialfind_package(Python COMPONENTS Interpreter)first, which fails without this fix.Supersedes #5814, which removed the guard completely.
Fixes #5813
Fixes #5472
Fixes #6063
Suggested changelog entry:
find_package(Python)from a parent project without the development components no longer breakspybind11_add_moduleor thepybind11::embedlink to Python.https://claude.ai/code/session_013JABmnjt9oAh29p1pytAB3