Improve Windows Installer (#12945)

1. If we couldn't verify installed OTP, don't quit but let user proceed with installing just Elixir

2. When checking installed OTPs, pick the recent most installed. Previously we were picking the first one which was basically guaranteed to be too old.

3. If we find an existing Elixir installation but it doesn't match the OTP version, offer to download the OTP version this Elixir installer was compiled against (which usually would be the newer version)

4. Add "Verify Erlang/OTP" button which re-checks for installed OTP.

Closes #12678.

Author: wojtekmach

Diff for: lib/elixir/scripts/windows_installer/installer.nsi

@@ -12,10 +12,18 @@ InstallDir "$PROGRAMFILES64\Elixir"
 
 Page custom CheckOTPPageShow CheckOTPPageLeave
 
-var Dialog
-var DownloadOTPLink
 var InstalledOTPRelease
 var OTPPath
+
+var Dialog
+var NoOTPLabel
+var NoOTPLabelCreated
+var OTPMismatchLabel
+var OTPMismatchLabelCreated
+var DownloadOTPLink
+var DownloadOTPLinkCreated
+var VerifyOTPButton
+var VerifyOTPButtonCreated
 Function CheckOTPPageShow
   !insertmacro MUI_HEADER_TEXT "Checking Erlang/OTP" ""
 
@@ -26,15 +34,61 @@ Function CheckOTPPageShow
     Abort
   ${EndIf}
 
-  EnumRegKey $0 HKLM "SOFTWARE\WOW6432NODE\Ericsson\Erlang" 0
-  ReadRegStr $0 HKLM "SOFTWARE\WOW6432NODE\Ericsson\Erlang\$0" ""
-  StrCpy $OTPPath $0
+  Call VerifyOTP
 
-  ${If} $OTPPath == ""
-    ${NSD_CreateLabel} 0 0   100% 20u "Couldn't find existing Erlang/OTP installation. Click the link below to download and install it before proceeding."
-    ${NSD_CreateLink}  0 25u 100% 20u "Download Erlang/OTP ${OTP_RELEASE}"
+  nsDialogs::Show
+FunctionEnd
+
+Function VerifyOTP
+  ${If} $NoOTPLabelCreated == "true"
+    ShowWindow $NoOTPLabel ${SW_HIDE}
+  ${EndIf}
+
+  ${If} $OTPMismatchLabelCreated == "true"
+    ShowWindow $OTPMismatchLabel ${SW_HIDE}
+  ${EndIf}
+
+  ${If} $DownloadOTPLinkCreated == "true"
+    ShowWindow $DownloadOTPLink ${SW_HIDE}
+  ${Else}
+    StrCpy $DownloadOTPLinkCreated "true"
+    ${NSD_CreateLink}  0 60u 100% 20u "Download Erlang/OTP ${OTP_RELEASE}"
     Pop $DownloadOTPLink
     ${NSD_OnClick} $DownloadOTPLink OpenOTPDownloads
+    ShowWindow $DownloadOTPLink ${SW_HIDE}
+  ${EndIf}
+
+  ${If} $VerifyOTPButtonCreated == "true"
+    ShowWindow $VerifyOTPButton ${SW_HIDE}
+  ${Else}
+    StrCpy $VerifyOTPButtonCreated "true"
+    ${NSD_CreateButton} 0 80u 25% 12u "Verify Erlang/OTP"
+    Pop $VerifyOTPButton
+    ${NSD_OnClick} $VerifyOTPButton VerifyOTP
+    ShowWindow $VerifyOTPButton ${SW_HIDE}
+  ${EndIf}
+
+  StrCpy $0 0
+  loop:
+    EnumRegKey $1 HKLM "SOFTWARE\WOW6432NODE\Ericsson\Erlang" $0
+    StrCmp $1 "" done
+    ReadRegStr $1 HKLM "SOFTWARE\WOW6432NODE\Ericsson\Erlang\$1" ""
+    StrCpy $OTPPath $1
+    IntOp $0 $0 + 1
+    goto loop
+  done:
+
+  ${If} $OTPPath == ""
+    ${If} $NoOTPLabelCreated != "true"
+      StrCpy $NoOTPLabelCreated "true"
+      ${NSD_CreateLabel} 0 0   100% 20u "Couldn't find existing Erlang/OTP installation. Click the link below to download and install it before proceeding."
+      Pop $NoOTPLabel
+    ${EndIf}
+
+    ShowWindow $NoOTPLabel ${SW_SHOW}
+    ShowWindow $DownloadOTPLink ${SW_SHOW}
+    ShowWindow $VerifyOTPButton ${SW_SHOW}
+
   ${Else}
     nsExec::ExecToStack `$OTPPath\bin\erl.exe -noinput -eval "\
     io:put_chars(erlang:system_info(otp_release)),\
@@ -45,24 +99,25 @@ Function CheckOTPPageShow
     ${If} $0 == 0
       StrCpy $InstalledOTPRelease $1
       ${If} $InstalledOTPRelease == ${OTP_RELEASE}
-        ${NSD_CreateLabel} 0 0 100% 20u "Found existing Erlang/OTP $InstalledOTPRelease installation at $OTPPath. Please proceed."
-      ${ElseIf} $2 < ${OTP_RELEASE}
-        ${NSD_CreateLabel} 0 0 100% 30u "Found existing Erlang/OTP $InstalledOTPRelease installation at $OTPPath but this Elixir installer was precompiled for Erlang/OTP ${OTP_RELEASE}. \
-        We recommend checking if there is an Elixir version precompiled for Erlang/OTP $InstalledOTPRelease. Otherwise, proceed."
+        ${NSD_CreateLabel} 0 0 100% 60u "Found existing Erlang/OTP $InstalledOTPRelease installation at $OTPPath. Please proceed."
+
       ${Else}
-        SetErrorlevel 5
-        MessageBox MB_ICONSTOP "Found existing Erlang/OTP $InstalledOTPRelease installation at $OTPPath but this Elixir version was precompiled for Erlang/OTP ${OTP_RELEASE}. \
-        Please upgrade your Erlang/OTP version or choose an Elixir installer matching your Erlang/OTP version"
-        Quit
+        ${If} $OTPMismatchLabelCreated != "true"
+          StrCpy $OTPMismatchLabelCreated "true"
+          ${NSD_CreateLabel} 0 0 100% 60u "Found existing Erlang/OTP $InstalledOTPRelease installation at $OTPPath but this Elixir installer was precompiled for Erlang/OTP ${OTP_RELEASE}. \
+          $\r$\n$\r$\nYou can either search for another Elixir installer precompiled for Erlang/OTP $InstalledOTPRelease or download Erlang/OTP ${OTP_RELEASE} and install before proceeding."
+          Pop $OTPMismatchLabel
+        ${EndIf}
+
+        ShowWindow $OTPMismatchLabel ${SW_SHOW}
+        ShowWindow $DownloadOTPLink  ${SW_SHOW}
+        ShowWindow $VerifyOTPButton  ${SW_SHOW}
       ${EndIf}
     ${Else}
       SetErrorlevel 5
       MessageBox MB_ICONSTOP "Found existing Erlang/OTP installation at $OTPPath but checking it exited with $0: $1"
-      Quit
     ${EndIf}
   ${EndIf}
-
-  nsDialogs::Show
 FunctionEnd
 
 Function OpenOTPDownloads
@@ -93,15 +148,18 @@ Function FinishPageShow
     Abort
   ${EndIf}
 
-  ${NSD_CreateCheckbox} 0 0 195u 10u "&Add $INSTDIR\bin to %PATH%"
-  Pop $AddElixirToPathCheckbox
-  SendMessage $AddElixirToPathCheckbox ${BM_SETCHECK} ${BST_CHECKED} 0
+  ; we add to PATH using erlang, so there must be an OTP installed to do so.
+  ${If} "$OTPPath" != ""
+    ${NSD_CreateCheckbox} 0 0 195u 10u "&Add $INSTDIR\bin to %PATH%"
+    Pop $AddElixirToPathCheckbox
+    SendMessage $AddElixirToPathCheckbox ${BM_SETCHECK} ${BST_CHECKED} 0
+
+    ${NSD_CreateCheckbox} 0 20u 195u 10u "&Add $OTPPath\bin to %PATH%"
+    Pop $AddOTPToPathCheckbox
+    SendMessage $AddOTPToPathCheckbox ${BM_SETCHECK} ${BST_CHECKED} 0
 
-  EnumRegKey $0 HKLM "SOFTWARE\WOW6432NODE\Ericsson\Erlang" 0
-  ReadRegStr $0 HKLM "SOFTWARE\WOW6432NODE\Ericsson\Erlang\$0" ""
-  ${NSD_CreateCheckbox} 0 20u 195u 10u "&Add $0\bin to %PATH%"
-  Pop $AddOTPToPathCheckbox
-  SendMessage $AddOTPToPathCheckbox ${BM_SETCHECK} ${BST_CHECKED} 0
+    ${NSD_CreateLabel} 0 40u 100% 20u "Note: you need to restart your shell for the environment variable changes to take effect."
+  ${EndIf}
 
   nsDialogs::Show
 FunctionEnd
@@ -145,9 +203,15 @@ var RemoveElixirFromPathCheckbox
 Function un.FinishPageShow
   !insertmacro MUI_HEADER_TEXT "Remove from %PATH%" ""
 
-  EnumRegKey $0 HKLM "SOFTWARE\WOW6432NODE\Ericsson\Erlang" 0
-  ReadRegStr $0 HKLM "SOFTWARE\WOW6432NODE\Ericsson\Erlang\$0" ""
-  StrCpy $OTPPath $0
+  StrCpy $0 0
+  loop:
+    EnumRegKey $1 HKLM "SOFTWARE\WOW6432NODE\Ericsson\Erlang" $0
+    StrCmp $1 "" done
+    ReadRegStr $1 HKLM "SOFTWARE\WOW6432NODE\Ericsson\Erlang\$1" ""
+    StrCpy $OTPPath $1
+    IntOp $0 $0 + 1
+    goto loop
+  done:
 
   nsDialogs::Create 1018
   Pop $Dialog