Binding Parameter Validation Expressions

[mathewc]

We should consider extending the syntax we have in place now for binding parameters (e.g. {age}) to allow declarative validations to also be specified (e.g. {age:int}). This would be similar to ASP.NET route parameter validation expressions (see here).

This would allow people to put declarative rules in place and error early with meaningful errors when chaining bindings together. E.g. if a QueueTrigger is bound to a Table input binding, the binding template for TableAttribute.Filter might be Age gt {age:int} and Location eq '{location:alpha}'. This will give errors earlier, rather than failing in the storage layer due to type mismatch error.

This might be even more useful in output binding scenarios, where you want to ensure data is sanitized before being stored (e.g. blob path components, document IDs, etc.)

[mathewc]

This issue is replaced by Azure/azure-webjobs-sdk#980, so closing this. If we do that work, Functions could build on that foundation to add a declarative trigger binding data validation model.