cue: separate closedness for lists and structs

Before embedded scalars, it was fine to "overload" IsClosed
for Lists and Structs. With embedded scalars, however,
whether embedded list is open or closed as a list and struct
are two orthogonal concepts. The API and code needs to
reflect this.

This also holds for API users. There is now a new "Allows"
method on Value to determine if a certain selector
is "fillable" on a Value. The special selectors
AnyString and AnyIndex have been added to allow querying
the possibility of setting a value.

Once closedness of definitions is handled properly
AnyDefinition should be added as well (note that hidden
labels are always allowed).

This deprecates the IsClosed method.

Remove the internal IsClosed method to ensure that a
decision made on what to use in all cases.

Fixes #879

Change-Id: I40334c8254435503bbd59a4f5d725ca415ff03b6
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/9325
Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>

cue/examples_test.go

@@ -65,3 +65,74 @@ bar: _foo
 	// 1 <nil>
 	// 2 <nil>
 }
+
+func ExampleValue_Allows() {
+	const file = `
+-- main.cue --
+a: [1, 2, ...int]
+
+b: #Point
+#Point: {
+	x:  int
+	y:  int
+	z?: int
+}
+
+c: [string]: int
+
+d: #C
+#C: [>"m"]: int
+`
+
+	v := load(file).Value()
+
+	a := v.LookupPath(cue.ParsePath("a"))
+	fmt.Println("a allows:")
+	fmt.Println("  index 4:       ", a.Allows(cue.Index(4)))
+	fmt.Println("  any index:     ", a.Allows(cue.AnyIndex))
+	fmt.Println("  any string:    ", a.Allows(cue.AnyString))
+
+	b := v.LookupPath(cue.ParsePath("b"))
+	fmt.Println("b allows:")
+	fmt.Println("  field x:       ", b.Allows(cue.Str("x")))
+	fmt.Println("  field z:       ", b.Allows(cue.Str("z")))
+	fmt.Println("  field foo:     ", b.Allows(cue.Str("foo")))
+	fmt.Println("  index 4:       ", b.Allows(cue.Index(4)))
+	fmt.Println("  any string:    ", b.Allows(cue.AnyString))
+
+	c := v.LookupPath(cue.ParsePath("c"))
+	fmt.Println("c allows:")
+	fmt.Println("  field z:       ", c.Allows(cue.Str("z")))
+	fmt.Println("  field foo:     ", c.Allows(cue.Str("foo")))
+	fmt.Println("  index 4:       ", c.Allows(cue.Index(4)))
+	fmt.Println("  any string:    ", c.Allows(cue.AnyString))
+
+	d := v.LookupPath(cue.ParsePath("d"))
+	fmt.Println("d allows:")
+	fmt.Println("  field z:       ", d.Allows(cue.Str("z")))
+	fmt.Println("  field foo:     ", d.Allows(cue.Str("foo")))
+	fmt.Println("  index 4:       ", d.Allows(cue.Index(4)))
+	fmt.Println("  any string:    ", d.Allows(cue.AnyString))
+
+	// Output:
+	// a allows:
+	//   index 4:        true
+	//   any index:      true
+	//   any string:     false
+	// b allows:
+	//   field x:        true
+	//   field z:        true
+	//   field foo:      false
+	//   index 4:        false
+	//   any string:     false
+	// c allows:
+	//   field z:        true
+	//   field foo:      true
+	//   index 4:        false
+	//   any string:     true
+	// d allows:
+	//   field z:        true
+	//   field foo:      false
+	//   index 4:        false
+	//   any string:     false
+}

cue/path.go

@@ -44,6 +44,32 @@ func (sel Selector) IsString() bool {
 	return sel.sel.kind() == adt.StringLabel
 }
 
+var (
+	// AnyField can be used to ask for any single label.
+	//
+	// In paths it is used to select constraints that apply to all elements.
+	// AnyField = anyField
+	anyField = Selector{sel: anySelector(adt.AnyLabel)}
+
+	// AnyDefinition can be used to ask for any definition.
+	//
+	// In paths it is used to select constraints that apply to all elements.
+	// AnyDefinition = anyDefinition
+	anyDefinition = Selector{sel: anySelector(adt.AnyDefinition)}
+
+	// AnyIndex can be used to ask for any index.
+	//
+	// In paths it is used to select constraints that apply to all elements.
+	AnyIndex = anyIndex
+	anyIndex = Selector{sel: anySelector(adt.AnyIndex)}
+
+	// AnyString can be used to ask for any regular string field.
+	//
+	// In paths it is used to select constraints that apply to all elements.
+	AnyString = anyLabel
+	anyLabel  = Selector{sel: anySelector(adt.AnyRegular)}
+)
+
 type selector interface {
 	String() string
 
@@ -355,6 +381,16 @@ func (s indexSelector) feature(r adt.Runtime) adt.Feature {
 	return adt.Feature(s)
 }
 
+// an anySelector represents a wildcard option of a particular type.
+type anySelector adt.Feature
+
+func (s anySelector) String() string        { return "_" }
+func (s anySelector) kind() adt.FeatureType { return adt.Feature(s).Typ() }
+
+func (s anySelector) feature(r adt.Runtime) adt.Feature {
+	return adt.Feature(s)
+}
+
 // TODO: allow import paths to be represented?
 //
 // // ImportPath defines a lookup at the root of an instance. It must be the first

cue/path_test.go

@@ -103,7 +103,7 @@ func Test(t *testing.T) {
 		path: ParsePath(`b[3T]`),
 		str:  "_|_",
 		err:  true,
-		out:  `_|_ // int label out of range (3000000000000 not >=0 and <= 268435455)`,
+		out:  `_|_ // int label out of range (3000000000000 not >=0 and <= 268435454)`,
 	}, {
 		path: ParsePath(`b[3.3]`),
 		str:  "_|_",

cue/testdata/benchmarks/deduparc.txtar

@@ -21,7 +21,7 @@ foo: #Value
 foo: #Value
 -- out/eval --
 (struct){
-  #Value: (struct){ |((#struct){
+  #Value: (#struct){ |((#struct){
       type: (string){ "float" }
     }, (#struct){
       type: (string){ "string" }

cue/testdata/benchmarks/dedupelem.txtar

@@ -27,7 +27,7 @@ foo.0.type: conflicting values "string" and "float":
 Result:
 (_|_){
   // [eval]
-  #Value: (struct){ |((#struct){
+  #Value: (#struct){ |((#struct){
       type: (string){ "int" }
     }, (#struct){
       type: (string){ "float" }

cue/testdata/builtins/closed.txtar

@@ -78,7 +78,7 @@ Result:
   inDisjunctions: (struct){
     x: (struct){
       socket: (#struct){
-        string: (struct){ |((#struct){
+        string: (#struct){ |((#struct){
             a: (#struct){
               b: (bool){ true }
             }
@@ -99,7 +99,7 @@ Result:
           }) }
       }
       syslog: (#struct){
-        string: (struct){ |((#struct){
+        string: (#struct){ |((#struct){
             a: (#struct){
               b: (bool){ true }
             }
@@ -118,7 +118,7 @@ Result:
               }
             }
           }) }
-        xxx: (struct){ |((#struct){
+        xxx: (#struct){ |((#struct){
             a: (#struct){
               b: (bool){ true }
             }

cue/testdata/comprehensions/issue843.txtar

@@ -81,7 +81,7 @@ package main
     #c: (list){
     }
   }
-  #o: (struct){ |((#struct){
+  #o: (#struct){ |((#struct){
       do: (string){ "f1" }
       as: (list){
       }

cue/testdata/cycle/structural.txtar

@@ -675,7 +675,7 @@ Result:
     #ref: (#struct){
       ref: (string){ string }
     }
-    x: (struct){ |((#struct){
+    x: (#struct){ |((#struct){
         c: (#list){
           0: ((string|struct)){ |((string){ string }, (#struct){
               ref: (string){ string }

cue/testdata/definitions/036_closing_with_failed_optional.txtar

@@ -109,7 +109,7 @@ v1:
   }
   #o2: (#struct){
   }
-  #d1: (struct){ |((#struct){
+  #d1: (#struct){ |((#struct){
       b: (int){ 4 }
     }, (#struct){
       c: (int){ 5 }

cue/testdata/definitions/embed.txtar

@@ -163,7 +163,7 @@ Result:
     }
   }
   reclose3: (struct){
-    #Step: (struct){ |((#struct){
+    #Step: (#struct){ |((#struct){
         Name: (string){ string }
         Something: (int){ int }
       }, (#struct){

cue/testdata/definitions/files.txtar

@@ -39,7 +39,7 @@ light: #theme & {
     ctermbg: (string){ "254" }
   }
   #Config: (#struct){
-    console: (struct){ |(*(#struct){
+    console: (#struct){ |(*(#struct){
         color: (string){ "light" }
         ctermbg: (string){ "254" }
       }, (#struct){

cue/testdata/definitions/issue342.txtar

@@ -33,13 +33,13 @@ Z: X.test_3_XXX.ref
     #Simple: (#struct){
       ref: (string){ string }
     }
-    #Complex: (struct){ |((#struct){
+    #Complex: (#struct){ |((#struct){
         ref: (string){ string }
       }, (#struct){
         local: (string){ string }
       }) }
     var: (string){ "XXX" }
-    test_1: (struct){ |((#struct){
+    test_1: (#struct){ |((#struct){
         ref: (string){ string }
       }, (#struct){
         local: (string){ string }

cue/testdata/definitions/issue419.txtar

@@ -22,7 +22,7 @@ l: [
   #B: (#struct){
     b: (string){ string }
   }
-  #X: (struct){ |((#struct){
+  #X: (#struct){ |((#struct){
       a: (string){ string }
     }, (#struct){
       b: (string){ string }

cue/testdata/definitions/issue471.txtar

@@ -24,7 +24,7 @@ package x
 }
 -- out/eval --
 (struct){
-  #a: (struct){ |((#struct){
+  #a: (#struct){ |((#struct){
       name: (string){ string }
       age: (int){ int }
     }, (#struct){

cue/testdata/disjunctions/elimination.txtar

@@ -185,17 +185,17 @@ preserveClosedness: medium: p3: {
 -- out/eval --
 (struct){
   disambiguateClosed: (struct){
-    b: (struct){ |((#struct){
+    b: (#struct){ |((#struct){
         x: (bool){ true }
       }, (#struct){
         y: (bool){ true }
       }) }
-    a: (struct){ |((#struct){
+    a: (#struct){ |((#struct){
         x: (bool){ true }
       }, (#struct){
         y: (bool){ true }
       }) }
-    #Def: (struct){ |((#struct){
+    #Def: (#struct){ |((#struct){
         x: (bool){ true }
       }, (#struct){
         y: (bool){ true }
@@ -364,13 +364,13 @@ preserveClosedness: medium: p3: {
   preserveClosedness: (struct){
     small: (struct){
       p1: (struct){
-        #A: (struct){ |(*(#struct){
+        #A: (#struct){ |(*(#struct){
             a: (string){ string }
           }, (#struct){
             a: (string){ string }
             b: (int){ int }
           }) }
-        #B: (struct){ |(*(#struct){
+        #B: (#struct){ |(*(#struct){
           }, (#struct){
             b: (int){ int }
           }, (#struct){
@@ -381,13 +381,13 @@ preserveClosedness: medium: p3: {
           }) }
       }
       p2: (struct){
-        #A: (struct){ |(*(#struct){
+        #A: (#struct){ |(*(#struct){
             a: (string){ string }
           }, (#struct){
             a: (string){ string }
             b: (int){ int }
           }) }
-        #B: (struct){ |(*(#struct){
+        #B: (#struct){ |(*(#struct){
           }, (#struct){
             a: (string){ string }
             b: (int){ int }
@@ -400,7 +400,7 @@ preserveClosedness: medium: p3: {
     }
     medium: (struct){
       p1: (struct){
-        #A: (struct){ |(*(#struct){
+        #A: (#struct){ |(*(#struct){
             a: (string){ string }
           }, (#struct){
             a: (string){ string }
@@ -409,7 +409,7 @@ preserveClosedness: medium: p3: {
             a: (string){ string }
             d: (string){ string }
           }) }
-        #B: (struct){ |(*(#struct){
+        #B: (#struct){ |(*(#struct){
           }, (#struct){
             c: (int){ int }
           }, (#struct){
@@ -433,7 +433,7 @@ preserveClosedness: medium: p3: {
           }) }
       }
       p2: (struct){
-        #A: (struct){ |(*(#struct){
+        #A: (#struct){ |(*(#struct){
             a: (string){ string }
           }, (#struct){
             a: (string){ string }
@@ -442,7 +442,7 @@ preserveClosedness: medium: p3: {
             a: (string){ string }
             d: (string){ string }
           }) }
-        #B: (struct){ |(*(#struct){
+        #B: (#struct){ |(*(#struct){
           }, (#struct){
             a: (string){ string }
             c: (int){ int }
@@ -466,7 +466,7 @@ preserveClosedness: medium: p3: {
           }) }
       }
       p3: (struct){
-        #A: (struct){ |(*(#struct){
+        #A: (#struct){ |(*(#struct){
             a: (string){ string }
           }, (#struct){
             a: (string){ string }
@@ -475,7 +475,7 @@ preserveClosedness: medium: p3: {
             a: (string){ string }
             d: (string){ string }
           }) }
-        #B: (struct){ |(*(#struct){
+        #B: (#struct){ |(*(#struct){
           }, (#struct){
             a: (string){ string }
             c: (int){ int }