fix cmakedeps multi conditional

conan/tools/cmake/cmakedeps/templates/target_data.py

@@ -93,12 +93,12 @@ def template(self):
               {% else %}
               set({{ pkg_name }}_COMPONENT_NAMES "")
               {% endif %}
-              {% if dependency_filenames %}
-              list(APPEND {{ pkg_name }}_FIND_DEPENDENCY_NAMES {{ dependency_filenames }})
-              list(REMOVE_DUPLICATES {{ pkg_name }}_FIND_DEPENDENCY_NAMES)
-              {% else %}
-              set({{ pkg_name }}_FIND_DEPENDENCY_NAMES "")
-              {% endif %}
+              if(DEFINED {{ pkg_name }}_FIND_DEPENDENCY_NAMES)
+                list(APPEND {{ pkg_name }}_FIND_DEPENDENCY_NAMES {{ dependency_filenames }})
+                list(REMOVE_DUPLICATES {{ pkg_name }}_FIND_DEPENDENCY_NAMES)
+              else()
+                set({{ pkg_name }}_FIND_DEPENDENCY_NAMES {{ dependency_filenames }})
+              endif()
               {% for dep_name, mode in dependency_find_modes.items() %}
               set({{ dep_name }}_FIND_MODE "{{ mode }}")
               {% endfor %}

conans/test/functional/toolchains/cmake/cmakedeps/test_cmakedeps.py

@@ -521,7 +521,7 @@ def test_private_transitive():
     client.run("install consumer -g CMakeDeps -s arch=x86_64 -s build_type=Release -of=. -v")
     client.assert_listed_binary({"dep/0.1": (NO_SETTINGS_PACKAGE_ID, "Skip")})
     data_cmake = client.load("pkg-release-x86_64-data.cmake")
-    assert 'set(pkg_FIND_DEPENDENCY_NAMES "")' in data_cmake
+    assert 'list(APPEND pkg_FIND_DEPENDENCY_NAMES )' in data_cmake
 
 
 @pytest.mark.tool("cmake")

conans/test/functional/toolchains/cmake/cmakedeps/test_cmakedeps_transitivity.py

@@ -147,9 +147,9 @@ class Pkg(ConanFile):
     c.run("install . -o engine*:shared=True")
     assert not os.path.exists(os.path.join(c.current_folder, f"matrix-release-{arch}-data.cmake"))
     cmake = c.load(f"engine-release-{arch}-data.cmake")
-    assert 'set(engine_FIND_DEPENDENCY_NAMES "")' in cmake
+    assert 'list(APPEND engine_FIND_DEPENDENCY_NAMES )' in cmake
 
     c.run("install . -o engine*:shared=True --build=engine*")
     assert not os.path.exists(os.path.join(c.current_folder, f"matrix-release-{arch}-data.cmake"))
     cmake = c.load(f"engine-release-{arch}-data.cmake")
-    assert 'set(engine_FIND_DEPENDENCY_NAMES "")' in cmake
+    assert 'list(APPEND engine_FIND_DEPENDENCY_NAMES )' in cmake

conans/test/functional/toolchains/cmake/cmakedeps/test_conditional_build_type.py

@@ -0,0 +1,101 @@
+import textwrap
+
+from conans.test.utils.tools import TestClient
+
+
+def test_conditional_build_type():
+    # https://github.com/conan-io/conan/issues/15851
+    c = TestClient()
+    c.run("new cmake_lib -d name=pkga -d version=0.1")
+    c.run("create . -s build_type=Debug -tf=")
+
+    c.save({}, clean_first=True)
+    c.run("new cmake_lib -d name=pkgb -d version=0.1 -d requires=pkga/0.1")
+    conanfile = textwrap.dedent("""
+        from conan import ConanFile
+        from conan.tools.cmake import CMakeToolchain, CMake, cmake_layout, CMakeDeps
+
+        class pkgbRecipe(ConanFile):
+            name = "pkgb"
+            version = "0.1"
+            package_type = "static-library"
+            settings = "os", "compiler", "build_type", "arch"
+            exports_sources = "CMakeLists.txt", "src/*", "include/*"
+
+            def layout(self):
+                cmake_layout(self)
+
+            def generate(self):
+                deps = CMakeDeps(self)
+                deps.generate()
+                tc = CMakeToolchain(self)
+                if self.settings.build_type == "Debug":
+                    tc.cache_variables["USE_PKGA"] = 1
+                    tc.preprocessor_definitions["USE_PKGA"] = 1
+                tc.generate()
+
+            def build(self):
+                cmake = CMake(self)
+                cmake.configure()
+                cmake.build()
+
+            def package(self):
+                cmake = CMake(self)
+                cmake.install()
+
+            def package_info(self):
+                self.cpp_info.libs = ["pkgb"]
+
+            def requirements(self):
+                if self.settings.build_type == "Debug":
+                    self.requires("pkga/0.1")
+        """)
+    cmake = textwrap.dedent("""\
+        cmake_minimum_required(VERSION 3.15)
+        project(pkgb CXX)
+
+        add_library(pkgb src/pkgb.cpp)
+        target_include_directories(pkgb PUBLIC include)
+
+        if(USE_PKGA)
+            find_package(pkga CONFIG REQUIRED)
+            target_link_libraries(pkgb PRIVATE pkga::pkga)
+        endif()
+
+        set_target_properties(pkgb PROPERTIES PUBLIC_HEADER "include/pkgb.h")
+        install(TARGETS pkgb)
+        """)
+    pkgb_cpp = textwrap.dedent(r"""
+        #include <iostream>
+        #include "pkgb.h"
+        #ifdef USE_PKGA
+        #include "pkga.h"
+        #endif
+
+        void pkgb(){
+            #ifdef USE_PKGA
+            pkga();
+            #endif
+
+            #ifdef NDEBUG
+            std::cout << "pkgb/0.1: Hello World Release!\n";
+            #else
+            std::cout << "pkgb/0.1: Hello World Debug!\n";
+            #endif
+        }
+        """)
+    c.save({"conanfile.py": conanfile,
+            "CMakeLists.txt": cmake,
+            "src/pkgb.cpp": pkgb_cpp})
+    c.run("create . -s build_type=Debug -tf=")
+    assert "pkga/0.1" in c.out
+    c.run("create . -s build_type=Release -tf=")  # without dep to pkga
+    assert "pkga" not in c.out
+
+    c.save({}, clean_first=True)
+    c.run("new cmake_lib -d name=pkgc -d version=0.1 -d requires=pkgb/0.1")
+    c.run("build . -s build_type=Debug")
+    c.run("build . -s build_type=Release")
+    # This used to crash because "pkga::pkga"
+    print(c.out)
+    print(c.current_folder)

conans/test/integration/test_components_error.py

@@ -51,5 +51,5 @@ class t3Conan(ConanFile):
     c.run("install t3")
 
     arch = c.get_default_host_profile().settings['arch']
-    assert 'set(t2_FIND_DEPENDENCY_NAMES "")' in c.load(f"t3/t2-release-{arch}-data.cmake")
+    assert 'list(APPEND t2_FIND_DEPENDENCY_NAMES )' in c.load(f"t3/t2-release-{arch}-data.cmake")
     assert not os.path.exists(os.path.join(c.current_folder, "t3/t1-config.cmake"))