Constraints - Generic Authoring

[bekir-ozturk]

Background

Allows restrict templates to be allowed to run / be visible only in case certain conditions are met.

Today, the engine has have very little insight into the context that a template is valid for. Aside from filtering based on language, all the installed templates are treated equally. This causes issues with filtering, install-time validation and instantiation-time validation.

For instance, it is possible to install & instantiate WPF project template on a Linux machine. It is also possible to add a Razor page into that WPF project.
Another example: it is possible for a user to instantiate an item template containing some C# 9.0 code into a project that has <LangVersion> set to 8.0.

In an ideal scenario, the engine should be able to filter templates depending on

• the operating system
• installed frameworks and tools together with supported version ranges (dotnet, NPM, SQL server, docker etc.)
• the project template that is currently in the working directory.
• installed optional workloads

Justification

This enables:

• Suggesting installation of missing components when instantiating a template
  • ex: Xamarin workload should be installed if the user is instantiating a 3rd party authored template that requires Xamarin
  • ex: .NET 6.0 if user is instantiating a template that requires features that are only available starting .NET 6.0.
• Listing only valid templates in the current machine/system-configuration/project when being presented to the users by hosts

Customer impact

1. Template authors will have a possibility to restrict templates to be run only in case certain conditions are met
2. Users will not see / be able to execute templates which cannot be executed for certain context - less chance for a mistake

Engineering impact

1. allows support for items templates inside Visual Studio

Sub tasks

done

• create design proposal and PoC
• design abstractions
• Edge implementation: TemplateConstraintManager class
• Orchestration: reading constraints configuration from template.json
• Utils: WellKnownSearchFilters for constraints
• constraint implementation: OS
• constraint implementation: host name and version
• Cli: implementation for instantiate
• Cli: list adaptation
• Cli: option to ignore the constraint
• Cli: adapt install\update template display after installation
• Cli: adapt tab completion
• Cli: adapt error handling on instantiation, allow --force to ignore constraints
• doc: Wiki documentation update
• doc: JSON schema update
• constraint implementation: SDK version
• constraint implementation: installed optional workloads

[vlada-shubina]

All the work is done