How to write template whether certain ExtraProperty is defined / has certain value

[k-nishizaki]

I want to know how to write template to check an item of ExtraProperties is defined or has certain value.

The only way I've found is the following, but it is ugly and cannot write else condition.
{{#each ExtraProperties}}{{#ifeq @key 'someKey'}}{{/ifeq}}{{/each}}

Is there any better way?

[k-nishizaki]

Finally I found that CustomProperties works with lookup in an expression.
The following is the sample:

public class TestConfigEditor : IConfigEditor
{
  public Task AfterPrepareAsync(IRootConfig config)
  {
    var cgc = (CodeGenConfig)config;
    foreach (var e in cgc.Entities)
    {
      foreach (var name in new string[] { "someKey", "anotherKey" })
      {
        bool exists = e.ExtraProperties?.ContainsKey(name) ?? false;
        e.CustomProperties[$"{name}Exists"] = exists;
        e.CustomProperties[name] = exists ? e.GetExtraProperty<JValue>(name).Value : null;
      }
    }
  }
}

After storing the value in CustomProperties, you can use the value in the template:

Custom existance: {{#if (lookup CustomProperties 'someKeyExists')}}exist{{else}}not exist{{/if}}
Custom conditional: {{#ifeq (lookup CustomProperties 'someKey') 'TheValue'}}true{{else}}false{{/ifeq}}

[k-nishizaki]

I found another solution.
in the ConfigEditor.AfterPrepareAsync, implement the following:

Handlebars.RegisterHelper("hasKey", (context, args) =>
{
    if (args.Length != 2)
        throw new System.ArgumentException("hasKey should receive collection and index");

    var index = args[1] as string;
    bool result = false;
    bool ContainsKeyInCollectionOf<T>()
    {
        var collection = args[0] as System.Collections.Generic.IDictionary<string, T>;
        if (collection != null && index != null)
        {
            result = collection.ContainsKey(index);
            return true;
        }
        return false;
    }

    if (args[0] == null)
      return false;
    // for ExtraProperties
    if (ContainsKeyInCollectionOf<JToken>())
        return result;
    // for CustomProperties
    if (ContainsKeyInCollectionOf<object>())
        return result;

    throw new System.ArgumentException("hasKey should receive IDictionary<string, JToken> or IDictionary<string, object>");
});

Handlebars.RegisterHelper("valueOf", (context, args) =>
{
    if (args.Length != 2)
        throw new System.ArgumentException("valueOf should receive collection and index");

    var index = args[1] as string;
    object result = null;
    bool GetValueInCollectionOf<T>(Func<T, object> converter)
    {
        var collection = args[0] as System.Collections.Generic.IDictionary<string, T>;
        if (collection != null && index != null)
        {
            T collectionValue;
            if (collection.TryGetValue(index, out collectionValue))
                result = converter(collectionValue);
            
            return true;
        }
        return false;
    }

    if (args[0] == null)
      return null;
    // for ExtraProperties
    if (GetValueInCollectionOf<JToken>(t => t.Value<string>()))
        return result;
    // for CustomProperties
    if (GetValueInCollectionOf<object>(t => t))
        return result;

    throw new System.ArgumentException("valueOf should receive IDictionary<string, JToken> or IDictionary<string, object>");
});

then, you can use the two functions hasKey and valueOf in your template:

Test Extra exist {{#if (hasKey ExtraProperties 'TestExist')}}true{{else}}false{{/if}}
Test Extra not exist {{#if (hasKey ExtraProperties 'TestNotExist')}}true{{else}}false{{/if}}
Test Custom exist {{#if (hasKey CustomProperties 'TestExist')}}true{{else}}false{{/if}}
Test Custom not exist {{#if (hasKey CustomProperties 'TestNotExistCustom')}}true{{else}}false{{/if}}

Test Value Extra exist {{#ifeq (valueOf ExtraProperties 'TestExist') 'Exist-Value'}}true{{else}}false{{/ifeq}}
Test Value Extra exist {{#ifeq (valueOf ExtraProperties 'TestNotExist') 'Exist-Value'}}true{{else}}false{{/ifeq}}
Test Value Custom exist {{#ifeq (valueOf CustomProperties 'TestExist') 'Exist-Value'}}true{{else}}false{{/ifeq}}
Test Value Custom exist {{#ifeq (valueOf CustomProperties 'TestNotExistCustom') 'Exist-Value'}}true{{else}}false{{/ifeq}}

I've tested the two functions against ExtraProperties and CustomProperties.