This change allows you to use generic-typed components without
explicitly specify type arguments.
**Before:**
```
<Grid Items="@MyItems" TItem="Person">
...
</Grid>
```
**After:**
```
<Grid Items="@MyItems">
...
</Grid>
```
Where possible, the type of the component will be inferred based on the
values passed to component parameters. This won't work like magic, you
have to specify parameters that provide type arguments for all of the
component's type parameters.
This is a best effort system, and it's largely based on the limitations
and behaviours of generic type inference in C#. We think it will work
well with most Blazor features and for most reasonable components. You
should not forget it's easy to specify type arguments, because you may
still have to in some cases.
In particular you may notice issues if you are trying to use a generic
typed component where all of the parameters are delegates or templates.
Type inference for delegates/lambdas in C# is based on the context. Any
time you combine generics and delegates it's easy to get into a scenario
where the compiler won't infer the correct type, or will give up.
----
The type inference feature works by generating a 'thunk' method in
*caller* that can act as a site for type inference (C# does not support
inference on constructors).
For our grid example above, the non-inferenced code will look something
like:
```
builder.OpenComponent<Grid<Person>>(0);
builder.AddAttribute(1, "Items", MyItems);
builder.CloseComponent();
```
Note that we can only write the type `Grid<Person>` because you wrote
`Person` in your code. What you type in the `TItem` attribute value gets
inserted into the generated code such that it fills in the generic type
parameter.
On the other hand, if you want is to infer the type, we have to do some
compiler magic. That looks like:
```
__Blazor.(long generated name).TypeInference.CreateGrid_0();
...
// elsewhere in the file
internal static class TypeInference
{
public static void CreateGrid_0<TItem>(RenderTreeBuilder builder,
int seq, int __seq0, global::System.Collections.Generic.List<TItem>
__arg0)
{
builder.OpenComponent<Grid<TItem>>(seq);
builder.AddAttribute(__seq0, "Items", __arg0);
builder.CloseComponent();
}
}
```
This allows us to rely on the C#
compiler for itype inference.
* Add the ability to discover generic types/properties
* Add @typeparam directive
Adds the ability to declare a generic-typed component using Razor.
* Add a 'type parameter' property to generic components
* Adds the ability to consume generic-typed components
* Test namespace cleanup
* Add recognication for RenderFragment in tag helpers
* Remove dead code from node writers
* refactor type check
* Continue to treat child content as a delegate in codegen
* Add extension to enumerate child content
* Reorganize code generation tests
These were growing a bit disorganized, and weren't really result in good
code reuse.
* fix test base class
* Add some child-content tests
* Add an explicit node for ChildContent
Adds a strongly typed node to represent a 'ChildContent' and what it
contains. This allows us to simplify the code generation path,
detect/processes more issues in IR passes, and will be essential for
supporting multiple child content.
* Ignore ChildContent in components when it's just whitespace
* Add diagnostic for duplicate child content
* Add support for explicit child content elements
Precursor to support for multiple child content items
* Add support for multiple child-content elements
* Change delegate signature for RenderFragment<T>
* Clean up Tag Helper constants
* Allow RenderFragment<T> as a child content
* Allow renaming the template parameter
* Improve error message for invalid child content
* Add diagnostic for repeated child content parameter names
* Add HTML Block rewriter
* Baseline updates
* test gaps
* Update some unit tests to represent same behavior as before
* Define Markup frame type. Tests for rendering markup frames into render tree.
* Support markup frames during diffing (retain, insert, update, delete)
* Support markup blocks on WebAssembly
* Support rendering markup frames with server-side execution too
* Support markup blocks with multiple top-level nodes. Support updating markup dynamically.
* Define MarkupString type as a way to insert dynamic markup without needing custom RenderFragment code
* Remove comment
* CR: Better null value handling
This change replaces the parsing of HTML that we perform during the code
generation phase, which parsing of HTML during the IR lowering phase.
The main benefit of this change is that the structure of the HTML is
reflected in the IR tree, allowing us to do more more advance
transformations.
As an example, see how the the handling of `<script>` tags is now a
separate pass.
As an aside from this I also redesigned the structure of component IR
nodes to match the new HTML element nodes. Passes are now more easily
aware of the nodes they are expected to handle and are more easily aware
of the difference between a component and element. This still isn't as
clean as I would like, but I think it's a reasonable improvement.
Another benefit of this is that the code generation is much simpler and
requires much less bookkeeping and statefulness.
Ports somee infrastructure and converts Razor code generation tests to use
it. This makes it much easier to make cross cutting changes to code
generation and see the effect.
Use build /p:GenerateBaselines=true to update all of the generated code
in place or when adding new tests. Generally if tests are failing, the
easiest thing to do is to update the baselines and do a git diff to see
what the deltas are.
The changes to the tests here are to use the new baseline infrastructure
and to rename classes/methods to result in shorter file paths.
Adds a little more use of Razor extensibility.
Razor is a plugin model, so we can't be the 'first mover' for initiating
compilation in the build tools and IDE.
Reorganizes tests and fills out more reusable test infrastructure for
Razor-driven testing.
Adds tests for declaration-only configuration.
Ryan Nowak
Steve Sanderson