Is there a way to extract rendered preset information from CMake? - cmake

Question

I have a CMakePresets.json file which makes use of inheritance and macro expansion.
Here is an excerpt, in reality I use multiple versions of "Foo":
{
"configurePresets": [
{
"name": "default",
"hidden": true,
"generator": "Unix Makefiles",
"binaryDir": "cmake-build-${presetName}",
"environment": {
"PATH": "/opt/foo/$env{FOO_VERSION}/bin:$penv{PATH}",
"LD_LIBRARY_PATH": "/opt/foo/$env{FOO_VERSION}.0/lib"
},
"cacheVariables": {
"FOO_VERSION": "$env{FOO_VERSION}",
}
},
{
"name": "debug-foo1",
"inherits": "default",
"environment": { "FOO_VERSION": "1" }
},
{
"name": "release-foo1",
"inherits": "debug-foo1",
"cacheVariables": { "CMAKE_BUILD_TYPE": "Release" }
}
],
"buildPresets": [
{
"name": "debug-foo1",
"configurePreset": "debug-foo1"
},
{
"name": "release-foo1",
"configurePreset": "release-foo1"
}
]
}
Now assume I select the preset release-foo1. This would render the following variables, among others:
binaryDir = "cmake-build-release-foo1"
FOO_VERSION = "1"
LD_LIBRARY_PATH = "/opt/foo/1.0/lib"
Is there a way to query these results for a given preset? For example, given release-foo1, I want to know the resulting binaryDir.
Of course I could parse the JSON myself, but that seems tedious, especially because of the cross references and substitutions which are being made by CMake.

Answer 1

You can use the -N flag to print the computed presets info without running the configure or generate steps. After modifying the presets file in your question to work, I created an empty CMakeLists.txt next to it and ran this test (*** stands in for my PATH):
$ cmake --preset=release-foo1 -N
Preset CMake variables:
CMAKE_BUILD_TYPE="Release"
FOO_VERSION="1"
Preset environment variables:
FOO_VERSION="1"
LD_LIBRARY_PATH="/opt/foo/1.0/lib"
PATH="/opt/foo/1/bin:***"
This is good enough for debugging your presets. If you need to go further, you could process the output using standard unix command line tools, like awk, grep, cut, etc.
I think this is the best you can do for now (CMake <=3.21) since there's nothing else in the command line documentation or the file API for IDEs that I could find.

Answer 2

Building on Alex Reinkings answer, you can get the binaryDir (and other parts) with the -N option if you tweek the preset a little bit.
You need to add a environment variable and reference it for binaryDir:.
See this tweeked example from CMake documentation:
{
"version": 2,
"cmakeMinimumRequired": {
"major": 3,
"minor": 20,
"patch": 0
},
"configurePresets": [
{
"name": "default",
"displayName": "Default Config",
"description": "Default build using Ninja generator",
"generator": "Ninja",
"binaryDir": "$env{BUILD_DIR}",
"cacheVariables": {
"FIRST_CACHE_VARIABLE": {
"type": "BOOL",
"value": "OFF"
},
"SECOND_CACHE_VARIABLE": "ON"
},
"environment": {
"BUILD_DIR": "${sourceDir}/build/default",
"MY_ENVIRONMENT_VARIABLE": "Test",
"PATH": "$env{HOME}/ninja/bin:$penv{PATH}"
},
"vendor": {
"example.com/ExampleIDE/1.0": {
"autoFormat": true
}
}
},
{
"name": "ninja-multi",
"inherits": "default",
"displayName": "Ninja Multi-Config",
"description": "Default build using Ninja Multi-Config generator",
"generator": "Ninja Multi-Config"
}
],
"buildPresets": [
{
"name": "default",
"configurePreset": "default"
}
],
"testPresets": [
{
"name": "default",
"configurePreset": "default",
"output": {"outputOnFailure": true},
"execution": {"noTestsAction": "error", "stopOnFailure": true}
}
],
"vendor": {
"example.com/ExampleIDE/1.0": {
"autoFormat": false
}
}
}
This will give you:
$ cmake --preset default -N
Preset CMake variables:
FIRST_CACHE_VARIABLE:BOOL="OFF"
SECOND_CACHE_VARIABLE="ON"
Preset environment variables:
=>BUILD_DIR="D:/tmp/presets/build/default"<=
MY_ENVIRONMENT_VARIABLE="Test"
PATH="..."