cmd/cue: add more gengotypes test cases for optional=nillable

To make sure that fields which normally generate as interfaces,
pointers, and references to named types will also work as expected.

While here, start using nil conversions for the gotest.go checks,
just so that we can consistently validate what each type ends up as
while at the same time sanity checking they can all be assigned to nil.

For #3760.

Signed-off-by: Daniel Martí <[email protected]>
Change-Id: I964367b0b945f68bd58b646c5e39dd191a0b40dd
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1214379
Reviewed-by: Roger Peppe <[email protected]>
Unity-Result: CUE porcuepine <[email protected]>
TryBot-Result: CUEcueckoo <[email protected]>

Author: mvdan

cmd/cue/cmd/testdata/script/exp_gengotypes.txtar

@@ -188,10 +188,10 @@ fail.both."42_LinkedList".types.LinkedList.next: conflicting values "x" and {ite
     ./root/types.cue:43:14
 fail.both.notList: conflicting values [1,2,3] and {embedded2?:int} (mismatched types list and struct):
     ./cuetest/all.cue:5:24
-    ./root/root.cue:127:2
+    ./root/root.cue:136:2
 fail.both.notString: conflicting values "not_a_struct" and {embedded2?:int} (mismatched types string and struct):
     ./cuetest/all.cue:4:24
-    ./root/root.cue:127:2
+    ./root/root.cue:136:2
 fail.cue."11_Int8".types.Int8: invalid value 99999 (out of bound <=127):
     ./cuetest/all.cue:61:30
 fail.cue."12_Int8".types.Int8: invalid value -99999 (out of bound >=-128):
@@ -251,6 +251,7 @@ import (
 	"slices"
 
 	"foo.test/bar/root"
+	imported "foo.test/bar/imported/subinst"
 )
 
 type Tests struct {
@@ -267,8 +268,9 @@ func main() {
 	var _ root.AttrChangedNameEmbed
 	var _ = root.AttrType(constant.Kind(0))
 
-	// It's easier to test the fields with a root value.
+	// It's easier to test the fields with zero values.
 	var zeroRoot root.Root
+	var zeroRootImports root.RootImports
 
 	var _ = zeroRoot.Embedded1
 	var _ = zeroRoot.Embedded2
@@ -282,12 +284,27 @@ func main() {
 	zeroRoot.DiscriminatorField = make(map[string]any)
 
 	// Optional fields which use the optional attribute flag.
+
 	zeroRoot.Fields.OptionalBasic = 5
 	zeroRoot.Fields.OptionalList = make([]int64, 0)
 	zeroRoot.Fields.OptionalMap = make(map[string]int64, 0)
-	zeroRoot.Fields.OptionalBasicAttrNillable = new(int64)
-	zeroRoot.Fields.OptionalListAttrNillable = new([]int64)
-	zeroRoot.Fields.OptionalMapAttrNillable = new(map[string]int64)
+
+	zeroRoot.Fields.OptionalTopAttrNillable = (*any)(nil)
+	zeroRoot.Fields.OptionalNullAttrNillable = (**struct{})(nil)
+	zeroRoot.Fields.OptionalBasicAttrNillable = (*int64)(nil)
+	zeroRoot.Fields.OptionalListAttrNillable = (*[]int64)(nil)
+
+	zeroRoot.Fields.OptionalInlineMapAttrNillable = (*map[string]int64)(nil)
+	zeroRoot.Fields.OptionalLocalMapAttrNillable = (*root.LocalMap)(nil)
+	zeroRoot.Fields.OptionalInlineNestedAttrNillable = (*struct{F *[]string `json:"f,omitempty"`})(nil)
+	zeroRoot.Fields.OptionalLocalNestedAttrNillable = (*root.LocalNested)(nil)
+
+	// #localNested is not affected by one of the references using optional=nullable.
+	var _ = root.LocalNested{F: []string{}}
+
+	zeroRootImports.OptionalRemoteMapAttrNillable = (*imported.RemoteMap)(nil)
+	zeroRootImports.OptionalRemoteNestedAttrNillable = (*imported.RemoteNested)(nil)
+
 	zeroRoot.Fields.OptionalStruct = root.EmptyStruct{}
 	zeroRoot.Fields.OptionalStructAttrType = root.EmptyStruct{}
 	zeroRoot.Fields.OptionalStructAttrZero = root.EmptyStruct{}
@@ -389,9 +406,18 @@ _#overridenNeverGenerate: string
 		optionalList?:  [...int]
 		optionalMap?:   [string]: int
 
+		optionalTopAttrNillable?:   _ @go(,optional=nillable)
+		optionalNullAttrNillable?:  null @go(,optional=nillable)
 		optionalBasicAttrNillable?: int @go(,optional=nillable)
 		optionalListAttrNillable?:  [...int] @go(,optional=nillable)
-		optionalMapAttrNillable?:   {[string]: int} @go(,optional=nillable)
+
+		// Ensure that "is nillable" is worked out correctly for inline types, referenced definitions,
+		// and nested types where only part of the type is not nillable, but not the top level.
+
+		optionalInlineMapAttrNillable?:    {[string]: int} @go(,optional=nillable)
+		optionalLocalMapAttrNillable?:     #localMap @go(,optional=nillable)
+		optionalInlineNestedAttrNillable?: {f?: [...string]} @go(,optional=nillable)
+		optionalLocalNestedAttrNillable?:  #localNested @go(,optional=nillable)
 
 		optionalStruct?: #emptyStruct
 		optionalStructAttrType?: #emptyStruct @go(,type=EmptyStruct)
@@ -498,6 +524,9 @@ _#hiddenStruct: {
 	}
 }
 
+#localMap: [string]: int
+#localNested: f?: [...string]
+
 // Hidden definitions are only generated if referenced; this one is not.
 _#unusedHiddenStruct: neverGenerate?: int
 
@@ -580,7 +609,7 @@ import (
 	"foo.test/bar/imported/unused"
 )
 
-#remoteStructs: {
+#rootImports: {
 	inst?: imported.#instanceStruct
 
 	lowerRegular?: imported.lowerRegular
@@ -590,6 +619,9 @@ import (
 
 	multiOne?: multipkg_one.#One
 	multiTwo?: multipkg_two.#Two
+
+	optionalRemoteMapAttrNillable?:     imported.#remoteMap @go(,optional=nillable)
+	optionalRemoteNestedAttrNillable?:  imported.#remoteNested @go(,optional=nillable)
 }
 
 _unusedImport: unused.#UnusedNeverGenerate
@@ -606,7 +638,7 @@ import (
 	"time"
 )
 
-type RemoteStructs struct {
+type RootImports struct {
 	Inst imported.InstanceStruct `json:"inst,omitempty"`
 
 	LowerRegular int64 `json:"lowerRegular,omitempty"`
@@ -620,6 +652,10 @@ type RemoteStructs struct {
 	MultiOne multipkg.One `json:"multiOne,omitempty"`
 
 	MultiTwo multipkg.Two `json:"multiTwo,omitempty"`
+
+	OptionalRemoteMapAttrNillable *imported.RemoteMap `json:"optionalRemoteMapAttrNillable,omitempty"`
+
+	OptionalRemoteNestedAttrNillable *imported.RemoteNested `json:"optionalRemoteNestedAttrNillable,omitempty"`
 }
 
 type Types struct {
@@ -703,11 +739,23 @@ type Root struct {
 
 		OptionalMap map[string]int64 `json:"optionalMap,omitempty"`
 
+		OptionalTopAttrNillable *any/* CUE top */ `json:"optionalTopAttrNillable,omitempty"`
+
+		OptionalNullAttrNillable **struct{}/* CUE null */ `json:"optionalNullAttrNillable,omitempty"`
+
 		OptionalBasicAttrNillable *int64 `json:"optionalBasicAttrNillable,omitempty"`
 
 		OptionalListAttrNillable *[]int64 `json:"optionalListAttrNillable,omitempty"`
 
-		OptionalMapAttrNillable *map[string]int64 `json:"optionalMapAttrNillable,omitempty"`
+		OptionalInlineMapAttrNillable *map[string]int64 `json:"optionalInlineMapAttrNillable,omitempty"`
+
+		OptionalLocalMapAttrNillable *LocalMap `json:"optionalLocalMapAttrNillable,omitempty"`
+
+		OptionalInlineNestedAttrNillable *struct {
+			F *[]string `json:"f,omitempty"`
+		} `json:"optionalInlineNestedAttrNillable,omitempty"`
+
+		OptionalLocalNestedAttrNillable *LocalNested `json:"optionalLocalNestedAttrNillable,omitempty"`
 
 		OptionalStruct EmptyStruct `json:"optionalStruct,omitempty"`
 
@@ -804,6 +852,12 @@ type Root struct {
 
 }
 
+type LocalMap map[string]int64
+
+type LocalNested struct {
+	F []string `json:"f,omitempty"`
+}
+
 type Root_innerStruct struct {
 	InnerStructField int64 `json:"innerStructField,omitempty"`
 }
@@ -861,6 +915,9 @@ lowerRegular: int
 UpperRegular: int
 #lowerDef: int
 #UpperDef: int
+
+#remoteMap: [string]: int
+#remoteNested: f?: [...string]
 -- imported/subinst/cue_types_imported_gen.go.want --
 // Code generated by "cue exp gengotypes"; DO NOT EDIT.
 
@@ -879,6 +936,12 @@ type InstanceStruct struct {
 type LowerDef int64
 
 type UpperDef int64
+
+type RemoteMap map[string]int64
+
+type RemoteNested struct {
+	F []string `json:"f,omitempty"`
+}
 -- imported/indirect/indirect.cue --
 package indirect