These changes support arbitrary combinations of input + plain types
within a schema. Handling plain types at the property level was not
sufficient to support such combinations. Reifying these types
required updating quite a bit of code. This is likely to have caused
some temporary complications, but should eventually lead to
substantial simplification in the SDK and program code generators.
With the new design, input and optional types are explicit in the schema
type system. Optionals will only appear at the outermost level of a type
(i.e. Input<Optional<>>, Array<Optional<>>, etc. will not occur). In
addition to explicit input types, each object type now has a "plain"
shape and an "input" shape. The former uses only plain types; the latter
uses input shapes wherever a plain type is not specified. Plain types
are indicated in the schema by setting the "plain" property of a type spec
to true.
Add a new package, `codegen/importer`, that can generate definitions for
resource states in PCL or TS/Python/C#/Go. The pipeline is relatively
simple: given a list of resource states, generate a PCL program in
memory, bind it, and pass it to the language-specific code generator.
This builds upon the existing PCL IR, and can be used with the currently
supported code generators.
Related to #1635.
