From 0c0830b2f2b9791d8d9e9e79da31df5115ad869c Mon Sep 17 00:00:00 2001
From: Don-Vito <khvitaly@gmail.com>
Date: Tue, 10 Nov 2020 00:55:45 +0200
Subject: [PATCH] Azure: fall back to powershell when no preferred shell is set
 (#8197)

I am still not sure what is the full set of scenarios that the problem
might occur, but for me it occurred for an "old" cloud shell account,
and didn't reproduce since I have reconfigured it. These behavior might
be explained by the fact that "preferred shell type" did not exist in
the API originally and thus was not set. In such case, Terminal
succeeds to retrieve to the settings but then crashes when reading the
missing field.  To fix it, I handle the case where the field is missing
and fallback to PowerShell.

## Validation Steps Performed
* Tested manually, only once.

Closes #7056
---
 .../TerminalConnection/AzureConnection.cpp    | 23 +++++++++++++++++--
 .../TerminalConnection/AzureConnection.h      |  2 ++
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/src/cascadia/TerminalConnection/AzureConnection.cpp b/src/cascadia/TerminalConnection/AzureConnection.cpp
index b8c5e31a0b9..9bddedb958b 100644
--- a/src/cascadia/TerminalConnection/AzureConnection.cpp
+++ b/src/cascadia/TerminalConnection/AzureConnection.cpp
@@ -687,6 +687,25 @@ namespace winrt::Microsoft::Terminal::TerminalConnection::implementation
         _state = AzureState::TermConnecting;
     }
 
+    // Method description:
+    // - Helper function to parse the preferred shell type from user settings returned by cloud console API.
+    // We need this function because the field might be missing in the settings
+    // created with old versions of cloud console API.
+    std::optional<utility::string_t> AzureConnection::_ParsePreferredShellType(const web::json::value& settingsResponse)
+    {
+        if (settingsResponse.has_object_field(L"properties"))
+        {
+            const auto userSettings = settingsResponse.at(L"properties");
+            if (userSettings.has_string_field(L"preferredShellType"))
+            {
+                const auto preferredShellTypeValue = userSettings.at(L"preferredShellType");
+                return preferredShellTypeValue.as_string();
+            }
+        }
+
+        return std::nullopt;
+    }
+
     // Method description:
     // - helper function to connect the user to the Azure cloud shell
     void AzureConnection::_RunConnectState()
@@ -706,9 +725,9 @@ namespace winrt::Microsoft::Terminal::TerminalConnection::implementation
         _WriteStringWithNewline(RS_(L"AzureSuccess"));
 
         // Request for a terminal for said cloud shell
-        const auto shellType = settingsResponse.at(L"properties").at(L"preferredShellType").as_string();
+        const auto shellType = _ParsePreferredShellType(settingsResponse);
         _WriteStringWithNewline(RS_(L"AzureRequestingTerminal"));
-        const auto socketUri = _GetTerminal(shellType);
+        const auto socketUri = _GetTerminal(shellType.value_or(L"pwsh"));
         _TerminalOutputHandlers(L"\r\n");
 
         // Step 8: connecting to said terminal
diff --git a/src/cascadia/TerminalConnection/AzureConnection.h b/src/cascadia/TerminalConnection/AzureConnection.h
index 4db0a9619b4..b2afd99ab2e 100644
--- a/src/cascadia/TerminalConnection/AzureConnection.h
+++ b/src/cascadia/TerminalConnection/AzureConnection.h
@@ -95,6 +95,8 @@ namespace winrt::Microsoft::Terminal::TerminalConnection::implementation
         std::optional<std::wstring> _ReadUserInput(InputMode mode);
 
         web::websockets::client::websocket_client _cloudShellSocket;
+
+        static std::optional<utility::string_t> _ParsePreferredShellType(const web::json::value& settingsResponse);
     };
 }