Short error messages for bad endpoints

Remove a very deep stack when presented with bad endpoints, including those with timeouts.

Author: ccreutzi

azureChat.m

@@ -4,7 +4,7 @@
 %   CHAT = azureChat(endpoint, deploymentID) creates an azureChat object with the
 %   endpoint and deployment ID path parameters required by Azure to establish the connection.
 %
-%   CHAT = azureChat(__,systemPrompt) creates an azureChatobject with the
+%   CHAT = azureChat(__,systemPrompt) creates an azureChat object with the
 %   specified system prompt.
 %
 %   CHAT = azureChat(__,Name=Value) specifies additional options
@@ -178,14 +178,25 @@
             end
 
             toolChoice = convertToolChoice(this, nvp.ToolChoice);
-            [text, message, response] = llms.internal.callAzureChatAPI(this.Endpoint, ...
-                this.DeploymentID, messagesStruct, this.FunctionsStruct, ...
-                ToolChoice=toolChoice, APIVersion = this.APIVersion, Temperature=this.Temperature, ...
-                TopProbabilityMass=this.TopProbabilityMass, NumCompletions=nvp.NumCompletions,...
-                StopSequences=this.StopSequences, MaxNumTokens=nvp.MaxNumTokens, ...
-                PresencePenalty=this.PresencePenalty, FrequencyPenalty=this.FrequencyPenalty, ...
-                ResponseFormat=this.ResponseFormat,Seed=nvp.Seed, ...
-                APIKey=this.APIKey,TimeOut=this.TimeOut, StreamFun=this.StreamFun);
+            try
+                [text, message, response] = llms.internal.callAzureChatAPI(this.Endpoint, ...
+                    this.DeploymentID, messagesStruct, this.FunctionsStruct, ...
+                    ToolChoice=toolChoice, APIVersion = this.APIVersion, Temperature=this.Temperature, ...
+                    TopProbabilityMass=this.TopProbabilityMass, NumCompletions=nvp.NumCompletions,...
+                    StopSequences=this.StopSequences, MaxNumTokens=nvp.MaxNumTokens, ...
+                    PresencePenalty=this.PresencePenalty, FrequencyPenalty=this.FrequencyPenalty, ...
+                    ResponseFormat=this.ResponseFormat,Seed=nvp.Seed, ...
+                    APIKey=this.APIKey,TimeOut=this.TimeOut, StreamFun=this.StreamFun);
+            catch ME
+                if ismember(ME.identifier,...
+                    ["MATLAB:webservices:UnknownHost","MATLAB:webservices:Timeout"])
+                    % throw(ME)would still print a long stack trace, from
+                    % ME.cause.stack. We cannot change ME.cause, so we
+                    % throw a new error:
+                    error(ME.identifier,ME.message);
+                end
+                rethrow(ME);
+            end
 
             if isfield(response.Body.Data,"error")
                 err = response.Body.Data.error.message;

tests/tazureChat.m

@@ -104,6 +104,19 @@ function errorsWhenPassingToolChoiceWithEmptyTools(testCase)
             testCase.verifyError(@()generate(chat,"input", ToolChoice="bla"), "llms:mustSetFunctionsForCall");
         end
 
+        function shortErrorForBadEndpoint(testCase)
+            chat = azureChat("https://nobodyhere.whatever/","deployment");
+            caught = false;
+            try
+                generate(chat,"input");
+            catch ME
+                caught = ME;
+            end
+            testCase.assertClass(caught,"MException");
+            testCase.verifyEqual(caught.identifier,'MATLAB:webservices:UnknownHost');
+            testCase.verifyEmpty(caught.cause);
+        end
+
         function invalidInputsConstructor(testCase, InvalidConstructorInput)
             testCase.verifyError(@()azureChat(getenv("AZURE_OPENAI_ENDPOINT"), getenv("AZURE_OPENAI_DEPLOYMENT"), InvalidConstructorInput.Input{:}), InvalidConstructorInput.Error);
         end