How to conditionally set first InstType in Component page - nsis

Question

I want to conditionally set the first Installation type in Component page based on checking if some files already exists on the machine.
I've already tried two different approachs. 1) using SetCurInstType, 2) conditionally defining the InstType sequence order on the basis of a "file exist" check.
Both the approaches have been tested using an UDF function. This UDF function has been used, alternatively, as input for the MUI_PAGE_CUSTOMFUNCTION_LEAVE of MUI_PAGE_LICENSE and for the MUI_PAGE_CUSTOMFUNCTION_PRE of MUI_PAGE_COMPONENTS.
Both tests didn't work as expected
Approach 1)
InstType "Install (all)"
InstType "Install (minimal)"
!define USER_ALL_INST_TYPE 1
!define USER_MIN_INST_TYPE 2
!define MUI_PAGE_CUSTOMFUNCTION_PRE SetInitInstType
!insertmacro MUI_PAGE_COMPONENTS
Section "1" Sec1
SectionIn ${USER_ALL_INST_TYPE} ${USER_MIN_INST_TYPE}
... other code
SectionEnd
Section "2" Sec2
SectionIn ${USER_ALL_INST_TYPE}
... other code
SectionEnd
Function SetInitInstType
IfFileExists "<file_path>" 0 endSetInitInstType
SetCurInstType ${USER_MIN_INST_TYPE}
endSetInitInstType:
FunctionEnd
Approach 2)
!define MUI_PAGE_CUSTOMFUNCTION_PRE SetInitInstType
!insertmacro MUI_PAGE_COMPONENTS
Section "1" Sec1
SectionIn ${USER_ALL_INST_TYPE} ${USER_MIN_INST_TYPE}
... other code
SectionEnd
Section "2" Sec2
SectionIn ${USER_ALL_INST_TYPE}
... other code
SectionEnd
Function SetInitInstType
IfFileExists "<file_path>" 0 SetAllInstType
InstType "Install (minimal)"
InstType "Install (all)"
!define USER_MIN_INST_TYPE 1
!define USER_ALL_INST_TYPE 2
Goto endSetInitInstType
SetAllInstType:
InstType "Install (all)"
InstType "Install (minimal)"
!define USER_ALL_INST_TYPE 1
!define USER_MIN_INST_TYPE 2
endSetInitInstType:
FunctionEnd
After Condition check, if file existed, the expected result would be that the Install Mode ComboBox in Component page was initialized with the "Install (minimal)" option
The actual result is instead as follow:
Approach 1) --> All sections are disabled and the Install Mode ComboBox is initialized with the "Custom" option
Approach 2) --> I receive an error during script compiling
Section: "1" ->(Sec1)
SectionIn: Usage: SectionIn InstTypeIdx [InstTypeIdx [...]]
Error in script "<script_name>.nsi" on line XXX -- aborting creation process
Any suggestion would be really appreciated

Answer 1

Don't ask me why but SectionIn uses a different index system than all the other inst type functions.
Unlike SectionIn the index is zero based, which means the first install type's index is 0
!include MUI2.nsh
!define MUI_PAGE_CUSTOMFUNCTION_PRE SetInitInstType
!insertmacro MUI_PAGE_COMPONENTS
!insertmacro MUI_PAGE_DIRECTORY
!insertmacro MUI_PAGE_INSTFILES
!insertmacro MUI_PAGE_FINISH
!insertmacro MUI_LANGUAGE "English"
!macro AddInstType name text
!define /IfNDef AddInstType_COUNTER 0
InstType "${text}"
!define INSTTYPE_${name}_IDX ${AddInstType_COUNTER} ; For SetCurInstType etc.
!define /ReDef /Math AddInstType_COUNTER ${AddInstType_COUNTER} + 1
!define INSTTYPE_${name}_SIN ${AddInstType_COUNTER} ; For SectionIn
!macroend
!insertmacro AddInstType ALL "Install (all)"
!insertmacro AddInstType MIN "Install (minimal)"
Section "1 (Both)" Sec1
SectionIn ${INSTTYPE_ALL_SIN} ${INSTTYPE_MIN_SIN}
SectionEnd
Section "2 (All only)" Sec2
SectionIn ${INSTTYPE_ALL_SIN}
SectionEnd
Function SetInitInstType
IfFileExists "$WinDir\Explorer.exe" 0 +2
SetCurInstType ${INSTTYPE_MIN_IDX}
FunctionEnd
Function .onInit
Call SetInitInstType ; In case installer is silent, force correct sections
FunctionEnd