🐛 Fix malformed include directories in exported nlohmann_json CMake targets for component-based installs (#1662) (#1663)

## Description

This PR fixes the problems observed with the 3.5.0 release while
updating in dependent MQT repositories.
There was a malformed include directory install command, that did not
even turn out to be necessary (through local testing with QCEC, QMAP,
and DDSIM).

This is essentially the forward port of #1662 and the `v3.5.1` release.

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additions, changes, fixes, or removals.
- [x] I have added migration instructions to the upgrade guide (if
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new warnings.
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- [x] I have reviewed my own code changes.

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---------

Signed-off-by: Lukas Burgholzer <burgholzer@me.com>

Author: burgholzer

CHANGELOG.md

@@ -28,6 +28,12 @@ This project adheres to [Semantic Versioning], with the exception that minor rel
 - 🔥 Remove the density matrix support from the MQT Core DD package ([#1466]) ([**@burgholzer**])
 - 🔥 Remove `datastructures` (`ds`) (sub)library from MQT Core ([#1458]) ([**@burgholzer**])
 
+## [3.5.1] - 2026-04-23
+
+### Fixed
+
+- 🐛 Fix malformed include directories in exported `nlohmann_json` CMake targets for component-based installs ([#1662]) ([**@burgholzer**])
+
 ## [3.5.0] - 2026-04-21
 
 _If you are upgrading: please see [`UPGRADING.md`](UPGRADING.md#350)._
@@ -216,6 +222,8 @@ _If you are upgrading: please see [`UPGRADING.md`](UPGRADING.md#330)._
 
 ## [3.2.0] - 2025-07-31
 
+_If you are upgrading: please see [`UPGRADING.md`](UPGRADING.md#320)._
+
 ### Added
 
 - 🐍 Build Python 3.14 wheels ([#1076]) ([**@denialhaag**])
@@ -334,7 +342,8 @@ _📚 Refer to the [GitHub Release Notes](https://github.com/munich-quantum-tool
 
 <!-- Version links -->
 
-[unreleased]: https://github.com/munich-quantum-toolkit/core/compare/v3.5.0...HEAD
+[unreleased]: https://github.com/munich-quantum-toolkit/core/compare/v3.5.1...HEAD
+[3.5.1]: https://github.com/munich-quantum-toolkit/core/releases/tag/v3.5.1
 [3.5.0]: https://github.com/munich-quantum-toolkit/core/releases/tag/v3.5.0
 [3.4.1]: https://github.com/munich-quantum-toolkit/core/releases/tag/v3.4.1
 [3.4.0]: https://github.com/munich-quantum-toolkit/core/releases/tag/v3.4.0
@@ -353,6 +362,7 @@ _📚 Refer to the [GitHub Release Notes](https://github.com/munich-quantum-tool
 <!-- PR links -->
 
 [#1664]: https://github.com/munich-quantum-toolkit/core/pull/1664
+[#1662]: https://github.com/munich-quantum-toolkit/core/pull/1662
 [#1652]: https://github.com/munich-quantum-toolkit/core/pull/1652
 [#1637]: https://github.com/munich-quantum-toolkit/core/pull/1637
 [#1635]: https://github.com/munich-quantum-toolkit/core/pull/1635

UPGRADING.md

@@ -37,6 +37,15 @@ The `datastructures` (sub)library has been removed from the MQT Core repository.
 Its functionality has only ever been used in [MQT QMAP] since its inception.
 As a consequence, the code shall be moved to [MQT QMAP] once QMAP adopts an MQT Core version that includes this change.
 
+## [3.5.1]
+
+No breaking changes.
+
+### Component-based CMake installs
+
+Fixed exported `nlohmann_json` CMake metadata so `find_package(mqt-core CONFIG)` no longer propagates an invalid `.../COMPONENT` include directory in component-based installations.
+Anyone relying on an installed version of `mqt-core` shall update from `3.5.0` to `3.5.1`.
+
 ## [3.5.0]
 
 The shared library ABI version (`SOVERSION`) is increased from `3.4` to `3.5`.
@@ -49,6 +58,9 @@ Any existing code that uses the `mqt-core` Python bindings will need to be recom
 
 ## [3.4.0]
 
+The shared library ABI version (`SOVERSION`) is increased from `3.3` to `3.4`.
+Thus, consuming libraries need to update their wheel repair configuration for `cibuildwheel` to ensure the `mqt-core` libraries are properly skipped in the wheel repair step.
+
 ### Python wheels
 
 This release contains two changes to the distributed wheels.
@@ -227,7 +239,8 @@ It also requires the `uv` library version 0.5.20 or higher.
 
 <!-- Version links -->
 
-[unreleased]: https://github.com/munich-quantum-toolkit/core/compare/v3.5.0...HEAD
+[unreleased]: https://github.com/munich-quantum-toolkit/core/compare/v3.5.1...HEAD
+[3.5.1]: https://github.com/munich-quantum-toolkit/core/compare/v3.5.0...v3.5.1
 [3.5.0]: https://github.com/munich-quantum-toolkit/core/compare/v3.4.0...v3.5.0
 [3.4.0]: https://github.com/munich-quantum-toolkit/core/compare/v3.3.0...v3.4.0
 [3.3.0]: https://github.com/munich-quantum-toolkit/core/compare/v3.2.0...v3.3.0

cmake/ExternalDependencies.cmake

@@ -191,12 +191,7 @@ if(MQT_CORE_JSON_INSTALL AND TARGET nlohmann_json)
     DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
     COMPONENT ${MQT_CORE_TARGET_NAME}_Development)
 
-  install(
-    TARGETS nlohmann_json
-    EXPORT ${MQT_CORE_JSON_TARGETS_EXPORT_NAME}
-    INCLUDES
-    DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
-    COMPONENT ${MQT_CORE_TARGET_NAME}_Development)
+  install(TARGETS nlohmann_json EXPORT ${MQT_CORE_JSON_TARGETS_EXPORT_NAME})
 
   install(
     EXPORT ${MQT_CORE_JSON_TARGETS_EXPORT_NAME}