chore: prevent null in heritage extends expressions (#41)

This is a temporary workaround to generate valid typescript. This
solution is not completely correct, and is subject to future change.

Author: Emyrk

convert.go

@@ -650,8 +650,21 @@ func (ts *Typescript) buildStruct(obj types.Object, st *types.Struct) (*bindings
 		// Adding a json struct tag causes the json package to consider
 		// the field unembedded.
 		if field.Embedded() && tag.Get("json") == "" {
+			// TODO: This prevents an inheritance clause from having a ` | null` in the
+			// expression. Typescript does not support `null` in the extends clause.
+			// This is not a perfect solution, and exists as a workaround.
+			// See https://github.com/coder/guts/issues/40
+			fieldType := field.Type()
+			for i := 0; i < 10; i++ { // Can there be an infinite loop here?
+				if ptrType, ok := fieldType.(*types.Pointer); ok {
+					fieldType = ptrType.Elem()
+					continue
+				}
+				break
+			}
+
 			// TODO: Generic args
-			heritage, err := ts.typescriptType(field.Type())
+			heritage, err := ts.typescriptType(fieldType)
 			if err != nil {
 				return tsi, xerrors.Errorf("heritage type: %w", err)
 			}

testdata/excludecustom/excludecustom.ts

@@ -4,4 +4,4 @@
 export interface Public {
     readonly PublicString: string;
     readonly PublicInt: number;
-}
+}

testdata/inheritance/inheritance.go

@@ -5,6 +5,11 @@ type Foo struct {
 	GenBar[string]
 }
 
+type FooBarPtr struct {
+	*Bar
+	GenBar[string]
+}
+
 type Bar struct {
 	BarField int
 }
@@ -17,7 +22,7 @@ type GenBar[T comparable] struct {
 // See: https://go.dev/play/p/-p6QYmY8mtR
 type FooBuzz struct {
 	Buzz `json:"foo"` // Json tag changes the inheritance
-	Bazz string       `json:"bazz"`
+	Bazz string `json:"bazz"`
 }
 
 type Buzz struct {

testdata/inheritance/inheritance.ts

@@ -16,6 +16,10 @@ export type Comparable = string | number | boolean;
 export interface Foo extends Bar, GenBar<string> {
 }
 
+// From codersdk/inheritance.go
+export interface FooBarPtr extends Bar, GenBar<string> {
+}
+
 // From codersdk/inheritance.go
 export interface FooBuzz {
     readonly foo: Buzz;