Ninja Multi-Config: Always generate build.ninja

If CMAKE_DEFAULT_BUILD_TYPE is not specified, use the first item
from CMAKE_CONFIGURATION_TYPES instead.

Help/generator/Ninja Multi-Config.rst

@@ -12,9 +12,10 @@ multiple configurations at once with :variable:`CMAKE_CONFIGURATION_TYPES`
 instead of only one configuration with :variable:`CMAKE_BUILD_TYPE`. One
 ``build-<Config>.ninja`` file will be generated for each of these
 configurations (with ``<Config>`` being the configuration name.) These files
-are intended to be run with ``ninja -f build-<Config>.ninja``. No
+are intended to be run with ``ninja -f build-<Config>.ninja``. A
-``build.ninja`` file is generated by default (see below for how to generate
+``build.ninja`` file is also generated, using the configuration from either
-it.)
+:variable:`CMAKE_DEFAULT_BUILD_TYPE` or the first item from
+:variable:`CMAKE_CONFIGURATION_TYPES`.
 
 ``cmake --build . --config <Config>`` will always use ``build-<Config>.ninja``
 to build. If no ``--config`` argument is specified, ``cmake --build .`` will
@@ -51,10 +52,10 @@ The ``Ninja Multi-Config`` generator recognizes the following variables:
 
 :variable:`CMAKE_DEFAULT_BUILD_TYPE`
   Specifies the configuration to use by default in a ``build.ninja`` file. If
-  this variable is specified, a ``build.ninja`` file is generated which uses
+  this variable is specified, ``build.ninja`` uses build rules from
-  build rules from ``build-<Config>.ninja`` by default. All custom commands are
+  ``build-<Config>.ninja`` by default. All custom commands are executed with
-  executed with this configuration. If the variable is not specified, no
+  this configuration. If the variable is not specified, the first item from
-  ``build.ninja`` file is generated.
+  :variable:`CMAKE_CONFIGURATION_TYPES` is used instead.
 
   The value of this variable must be one of the items from
   :variable:`CMAKE_CONFIGURATION_TYPES`.

Source/cmGlobalNinjaGenerator.cxx

@@ -2488,8 +2488,7 @@ bool cmGlobalNinjaMultiGenerator::OpenBuildFileStreams()
       return false;
     }
     *this->DefaultFileStream
-      << "# This file is a convenience file generated by\n"
+      << "# Build using rules for '" << this->DefaultFileConfig << "'.\n\n"
-      << "# CMAKE_DEFAULT_BUILD_TYPE.\n\n"
       << "include " << GetNinjaImplFilename(this->DefaultFileConfig) << "\n\n";
   }
 
@@ -2606,9 +2605,6 @@ bool cmGlobalNinjaMultiGenerator::InspectConfigTypeVariables()
 
 std::string cmGlobalNinjaMultiGenerator::GetDefaultBuildConfig() const
 {
-  if (this->DefaultFileConfig.empty()) {
-    return "Debug";
-  }
   return "";
 }
 
@@ -2625,8 +2621,10 @@ bool cmGlobalNinjaMultiGenerator::ReadCacheEntriesForBuild(
 
   this->DefaultFileConfig =
     state.GetSafeCacheEntryValue("CMAKE_DEFAULT_BUILD_TYPE");
-  if (!this->DefaultFileConfig.empty() &&
+  if (this->DefaultFileConfig.empty()) {
-      !configs.count(this->DefaultFileConfig)) {
+    this->DefaultFileConfig = configsVec.front();
+  }
+  if (!configs.count(this->DefaultFileConfig)) {
     std::ostringstream msg;
     msg << "The configuration specified by "
         << "CMAKE_DEFAULT_BUILD_TYPE (" << this->DefaultFileConfig

Tests/RunCMake/NinjaMultiConfig/InvalidDefaultConfigsNoDefaultFile-result.txt

@@ -1 +0,0 @@
-1

Tests/RunCMake/NinjaMultiConfig/InvalidDefaultConfigsNoDefaultFile-stderr.txt

@@ -1,6 +0,0 @@
-^CMake Error:
-  CMAKE_DEFAULT_CONFIGS cannot be used without CMAKE_DEFAULT_BUILD_TYPE or
-  CMAKE_CROSS_CONFIGS
-
-
-CMake Generate step failed\.  Build files cannot be regenerated correctly\.$

Tests/RunCMake/NinjaMultiConfig/RunCMakeTest.cmake

@@ -81,7 +81,9 @@ endfunction()
 set(RunCMake_TEST_NO_CLEAN 1)
 
 set(RunCMake_TEST_BINARY_DIR ${RunCMake_BINARY_DIR}/Simple-build)
-set(RunCMake_TEST_OPTIONS "-DCMAKE_CONFIGURATION_TYPES=Debug\\;Release\\;MinSizeRel\\;RelWithDebInfo;-DCMAKE_DEFAULT_BUILD_TYPE=RelWithDebInfo;-DCMAKE_CROSS_CONFIGS=all")
+# IMPORTANT: Setting RelWithDebInfo as the first item in CMAKE_CONFIGURATION_TYPES
+# generates a build.ninja file with that configuration
+set(RunCMake_TEST_OPTIONS "-DCMAKE_CONFIGURATION_TYPES=RelWithDebInfo\\;Debug\\;Release\\;MinSizeRel;-DCMAKE_CROSS_CONFIGS=all")
 run_cmake_configure(Simple)
 unset(RunCMake_TEST_OPTIONS)
 include(${RunCMake_TEST_BINARY_DIR}/target_files.cmake)
@@ -153,10 +155,6 @@ set(RunCMake_TEST_OPTIONS "-DCMAKE_CROSS_CONFIGS=Debug\\;Release;-DCMAKE_DEFAULT
 run_cmake(InvalidDefaultConfigsCross)
 unset(RunCMake_TEST_OPTIONS)
 
-set(RunCMake_TEST_OPTIONS "-DCMAKE_CROSS_CONFIGS=Debug\\;Release;-DCMAKE_DEFAULT_CONFIGS=all")
-run_cmake(InvalidDefaultConfigsNoDefaultFile)
-unset(RunCMake_TEST_OPTIONS)
-
 set(RunCMake_TEST_OPTIONS "-DCMAKE_DEFAULT_BUILD_TYPE=Release;-DCMAKE_DEFAULT_CONFIGS=all")
 run_cmake(InvalidDefaultConfigsNoCross)
 unset(RunCMake_TEST_OPTIONS)