[feature/constraints] Template constraints proposal #4593
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#4606 may help with the review, it contains |
docs/design/constraints.md
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| `dotnet new` will implement the following changes based on constraints: | ||
| - the template which is not allowed in the context will not be shown in `dotnet new list` output | ||
| - additional option (`--force`) may be considered to show all the templates anyway |
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Plus it might be good idea for the debug output to contain the context of the constraint evaluated (value of variables) - for easier troubleshooting.
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would it be more useful to output it always in verbose mode? (basically output it in debug output which is shown in verbose mode)
docs/design/constraints.md
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| ``` | ||
| When creating the constraint, it is assumed that constraint will be initialized and its context will be evaluated. | ||
| Example: if constraint needs to know the project MSBuild properties it is assumed that project will be identified and MSBuild properties will be evaluated when the constraint is being created prior to first evaluation. | ||
| Template constraints initialization will be started in parallel once `IEngineEnvironmentSettings` are created. The methods that work with constraint will ensure task completion before evaluation. |
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What happens if the Task is not yet complete when evaluation is already called? Will it block untill constraint is fully initialized? This can probably create suboptimal experience with tab completion. For this case we might want to consider adding a mechanism to wait for predefined timespan for the constraint to be intialized (e.g. Task<bool> WaitForInitialization(TimeSpan span)). Tab completition might then wait just for a brief delay and then consider the constraint not to be met (or otherwise - depending on desired behavior).
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Yes, correctly. Methods of TemplateConstraintManager - the class to be used when working with constraints - will wait until required constraint is initialized.
It makes total sense to add a timeout for constraint evaluation for tab completion and only return information about those constraints that could be initialized. I think it might just be an additional parameter to methods of TemplateConstraintManager.
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Thinking more (and implementation wise) it's up to a caller to define the timeout. So, it didn't make it to API.
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Looks great! And thanks for taking the time to putting this in writing.
Aside from my comments, I have one question:
Should we make a clear decision on whether constraint initializations can be executed in parallel?
If yes, we will need to be more careful when implementing new constraints, but we may get some nice performance benefits in the long run.
If we decide that they will be executed in a serialized way, it may be difficult to make it parallelizable later. So, this may be a good time to consider pros and cons.
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#3107
template constraints feature proposal