How to user Prompt Template with Vertex AI Chat Completion?

[weirdyang]

I'm trying to learn how to use the prompt templates, but when I try this code, I get the error Required service of type Microsoft.SemanticKernel.TextGeneration.ITextGenerationService not registered.

I think I need to include a prompt execution settings, or pass in my service id somehow, but InvokeAsync does not see to have a parameter for it.

             var template = await File.ReadAllTextAsync("Assets/arc_ops_prompt_2.txt");

            var arguments = new KernelArguments()
            {
                { "customer", new
                    {
                        name = user.Name,
                        role = user.Role,
                        data = !string.IsNullOrWhiteSpace(user.Name) && !string.IsNullOrWhiteSpace(user.Role)
                    }
                },
                { "history", new[]
                    {
                        new { role = "user", content = user.Query },
                    }
                },
            };
            GeminiPromptExecutionSettings settings = new()
            {
                ToolCallBehavior = GeminiToolCallBehavior.AutoInvokeKernelFunctions,
                ServiceId = ServiceName
            };
            var templateFactory = new HandlebarsPromptTemplateFactory();
            var promptTemplateConfig = new PromptTemplateConfig()
            {
                Template = template,
                TemplateFormat = "handlebars",
                Name = "QueryPrompt",
                // pass in execution settings here?
            };

            var function = kernel.CreateFunctionFromPrompt(promptTemplateConfig, templateFactory);
            var response = await kernel.InvokeAsync(function, arguments);

and when I check my rendered prompt, the history isn't rendered:

User: ?!?!
Assistant: Sorry, I can not help with that.
</message>
{% for item in history %}
<message role="">
    
</message>
{% endfor %}

here's how it looks in my template:

{% for item in history %}
<message role="{{item.role}}">
    {{item.content}}
</message>
{% endfor %}

I tested it with the template from the sample https://learn.microsoft.com/en-us/semantic-kernel/concepts/prompts/handlebars-prompt-templates?pivots=programming-language-csharp, and it doesn't work either:

    Make sure to reference the customer by name response.
</message>
{% for item in history %}
<message role="">
    
</message>
{% endfor %}
``

[sophialagerkranspandey]

We've created an issue with Vertex AI for tracking: #10889

[weirdyang]

Thanks but this discussion is for 2 separate issues.

I resolved the first one, the second one seems to be an issue with the documentation for handlebars prompt template.