Yaml format for config

Let's rework the format of config. Currently, the used format (ksb) is a completely custom. This is bad, as no one editor has syntax highlighting for it (except Kate, but that has its own limitation, and is constantly outdated).

The reason why I am arising this question now is that, as discussed in Matrix, some people want to stay in kdesrc-build forever, and keeping the module definitions common with kdesrc-build limits the kde-builder for a long time from moving forward (such as implementing project-based deps resolution). So, it was told that we should have separate definitions for kde-builder. And, as in this case definitions files will anyway loose the file history, this is the best time to finally change format to yaml.

I prepared the following example of the config, and the same syntax will be used in module-definitions in yaml format. Want to request comments on the format.

kde-builder_config.yaml:

# RFC example yaml config

# Specify the "version" of the config syntax. For the cases when in the future some fields may change, such as some option was scalar, but then needs to be a list.
config-version: 2

global:
  # variable declaration:
  _ver: 6
# _build_with_qt6: OFF
  _build_with_qt6: "ON"  # Better quote such value, but we could make that parsable even without quotes.

  async: true

  # variable usage:
  branch-group: kf${_ver}-qt${_ver}
#  branch-group: kf5-qt5
#  branch-group: kf6-qt6
#  branch-group: stable-kf5-qt5
#  branch-group: stable-kf6-qt6

  include-dependencies: true

  source-dir: ~/kde${_ver}/src
  build-dir: ~/kde${_ver}/build
  install-dir: ~/kde${_ver}/usr
  log-dir: ~/kde${_ver}/log

  qt-install-dir: ~/kde${_ver}/usr-qt

  # cmake-options - variant 1 - as a multiline string
  cmake-options: >
    -DCMAKE_BUILD_TYPE=Debug -DQT_MAJOR_VERSION=${_ver}
    -DBUILD_WITH_QT6=${_build_with_qt6} -DPython3_FIND_VIRTUALENV=STANDARD -DSOME_OTHER_OPTION="VALUE with space"
    -DPython3_FIND_UNVERSIONED_NAMES=FIRST

  num-cores: 10
# num-cores-low-mem auto
  num-cores-low-mem: 2

  cmake-generator: Ninja

  install-login-session: true

  # Stop the build process on the first failure
  stop-on-failure: true
#    stop-on-failure false

  # Build with LSP support for everything that supports it
  compile-commands-export: true
  compile-commands-linking: true


  ignore-modules:
    - gpgme
    - libgpg-error

  # Or equivalent in one line (can be used interchangeably):
  ignore-modules: [custom-qt${_ver}-libs, gpgme]

  persistent-data-file: ~/kde${_ver}/persistent-options.json
  generate-vscode-project-config: true
  generate-clion-project-config: true
  source-when-start-program: ~/kde6/qt_logging_environment.sh

  # The key-value dict option
  set-env:
    _GLO: "glo val"
    PKG_CONFIG_PATH: /usr/lib/pkgconfig
    LD_LIBRARY_PATH: /usr/lib
    QT_LOGGING_RULES: ark*=true;kf.coreaddons=false;kf.service.services=false;kf.service.sycoca=false;qt.qpa.wayland=false;kf.moretools=false;default=false

  # dict
  git-repository-base:
    qt6-copy: https://invent.kde.org/qt/qt/
    something: something/

  # for now, as a string
  configure-flags: "configure-flags --enable-maintainer-mode --enable-languages=cpp,qt6 --disable-gpgconf-test --disable-gpg-test --disable-gpgsm-test --disable-g13-test"

  # for now, as a string
  do-not-compile: one two three

  # for now, as a string
  make-install-prefix: "one two"

  # for now, as a string
  ninja-options: "-j 99"

  # for now, as a string
  qmake-options: "-j 99"

  # for now, as a string
  make-options: "-j 99"

  phase-selection:  # candidate for combining with filter-out-phases
    - no-src
    - build-only
    - no-install
    - no-tests

!include ${module-definitions-dir}/kf${_ver}-qt${_ver}.yaml
# Another include. Should not indicate "duplicate key error".
!include ${module-definitions-dir}/kf${_ver}-qt${_ver}_2.yaml

# Declaration of a module (i.e. it does not exist in standard module definitions)
crashinator:
  repository: kde:sitter/crashinator.git

# Module-sets syntax. Variant 1 - with trailing "/"
frameworks/:
  repository: kde-projects
  use-modules:
    - frameworks/*
    - kcalc
    - dolphin
  ignore-modules:
    - graphics/*
    - kdelibs4support
    - kdewebkit
    - kdesignerplugin
    - kemoticons
    - kxmlrpcclient
  cmake-options: >
    -DBUILD_WITH_QT6=ON

# Module-sets syntax. Variant 2 - with "< >" brackets
<frameworks>:
  use-modules:
    - one
    - two
    - three
  ignore-modules:
    - kdelibs4support
    - kdewebkit
    - khtml
    - kjsembed

# Module-sets syntax. Variant 3 - with "( )" surrounding.
(frameworks):
  use-modules:
    - one
    - two
    - three


# Replacement for "options kompare"
+kompare:
  set-env:
    SomeVar: some-val

+qt6-set:
  source-dir: ~/kde6/src-qt
  build-dir: ~/kde6/build-qt
  branch: dev

+kcoreaddons:
  # Another way for cmake-options. As a list.
  cmake-options:
    - -DCMAKE_BUILD_TYPE=Debug
    - -DQT_MAJOR_VERSION=${_ver}
    # comment in the middle of list
    - -DBUILD_WITH_QT6=${_build_with_qt6}
    - -DPython3_FIND_VIRTUALENV=STANDARD  # comment in the end of line
    - -DPython3_FIND_UNVERSIONED_NAMES=FIRST

+kio:
  branch: "1.2"  # quoting to force string type.


# "+" (options) can also apply to module set (project group).
+frameworks:
  ignore-modules:
    - kcalc

# Possibly, it may be a bit confusing in that if it is applying to module or module-set (the same as with options block now).
# We can optionally allow trailing slash to indicate the module-set (just for human readability):
+frameworks/:
  ignore-modules:
    - kcalc

Tagging people that probably are interested to discuss this: @duha @merritt @bcooksley @tcanabrava @thiagosueto @nclarius