encoding/jsonschema: use allowedTypes in if/then/else constraints

Unlike, `allOf` and friends, the `if/then/else` logic was not benefiting
from the fact that we can eliminate some elements from the disjunctions
created in the subschemas. By doing this, we improve performance
in some schemas by quite a bit (for example, it improved vet time
on one of the SchemaStore schemas [1] by 40%).

[1] https://github.com/SchemaStore/schemastore/blob/64f44fd870573eff20d44582f83edac5907e543e/src/schemas/json/dependabot-2.0.json

Signed-off-by: Roger Peppe <[email protected]>
Change-Id: I0e4aca10c1bec02cb6820db1c17953b21bd29760
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1202609
TryBot-Result: CUEcueckoo <[email protected]>
Unity-Result: CUE porcuepine <[email protected]>
Reviewed-by: Daniel Martí <[email protected]>

encoding/jsonschema/constraints_combinator.go

@@ -177,13 +177,45 @@ func constraintNot(key string, n cue.Value, s *state) {
 }
 
 func constraintIf(key string, n cue.Value, s *state) {
-	s.ifConstraint = s.schema(n)
+	s.ifConstraint = n
 }
 
 func constraintThen(key string, n cue.Value, s *state) {
-	s.thenConstraint = s.schema(n)
+	s.thenConstraint = n
 }
 
 func constraintElse(key string, n cue.Value, s *state) {
-	s.elseConstraint = s.schema(n)
+	s.elseConstraint = n
+}
+
+// constraintIfThenElse is not implemented as a standard constraint
+// function because it needs to operate knowing about the presence
+// of all of "if", "then" and "else".
+func constraintIfThenElse(s *state) {
+	hasIf, hasThen, hasElse := s.ifConstraint.Exists(), s.thenConstraint.Exists(), s.elseConstraint.Exists()
+	if !hasIf || (!hasThen && !hasElse) {
+		return
+	}
+	var ifExpr, thenExpr, elseExpr ast.Expr
+	ifExpr, ifSub := s.schemaState(s.ifConstraint, s.allowedTypes, nil)
+	if hasThen {
+		// The allowed types of the "then" constraint are constrained both
+		// by the current constraints and the "if" constraint.
+		thenExpr, _ = s.schemaState(s.thenConstraint, s.allowedTypes&ifSub.allowedTypes, nil)
+	}
+	if hasElse {
+		elseExpr, _ = s.schemaState(s.elseConstraint, s.allowedTypes, nil)
+	}
+	if thenExpr == nil {
+		thenExpr = top()
+	}
+	if elseExpr == nil {
+		elseExpr = top()
+	}
+	s.all.add(s.pos, ast.NewCall(
+		ast.NewIdent("matchIf"),
+		ifExpr,
+		thenExpr,
+		elseExpr,
+	))
 }

encoding/jsonschema/decode.go

@@ -423,9 +423,9 @@ type state struct {
 	minContains *uint64
 	maxContains *uint64
 
-	ifConstraint   ast.Expr
-	thenConstraint ast.Expr
-	elseConstraint ast.Expr
+	ifConstraint   cue.Value
+	thenConstraint cue.Value
+	elseConstraint cue.Value
 
 	schemaVersion        Version
 	schemaVersionPresent bool
@@ -501,7 +501,6 @@ func (s *state) finalize() (e ast.Expr) {
 		// we might be inside an allOf or oneOf with other valid constraints.
 		return bottom()
 	}
-	s.addIfThenElse()
 
 	conjuncts := []ast.Expr{}
 	disjuncts := []ast.Expr{}
@@ -651,24 +650,6 @@ outer:
 	return e
 }
 
-func (s *state) addIfThenElse() {
-	if s.ifConstraint == nil || (s.thenConstraint == nil && s.elseConstraint == nil) {
-		return
-	}
-	if s.thenConstraint == nil {
-		s.thenConstraint = top()
-	}
-	if s.elseConstraint == nil {
-		s.elseConstraint = top()
-	}
-	s.all.add(s.pos, ast.NewCall(
-		ast.NewIdent("matchIf"),
-		s.ifConstraint,
-		s.thenConstraint,
-		s.elseConstraint,
-	))
-}
-
 func (s *state) comment() *ast.CommentGroup {
 	// Create documentation.
 	doc := strings.TrimSpace(s.title)
@@ -782,6 +763,7 @@ func (s0 *state) schemaState(n cue.Value, types cue.Kind, idRef []label) (ast.Ex
 			c.fn(key, value, s)
 		})
 	}
+	constraintIfThenElse(s)
 
 	return s.finalize(), s
 }

encoding/jsonschema/testdata/external/tests/draft2020-12/dynamicRef.json

@@ -748,8 +748,8 @@
 			}
 		},
 		"skip": {
-			"v2": "extract error: keyword \"$dynamicAnchor\" not yet implemented (and 3 more errors)",
-			"v3": "extract error: keyword \"$dynamicAnchor\" not yet implemented (and 3 more errors)"
+			"v2": "extract error: keyword \"$dynamicRef\" not yet implemented (and 3 more errors)",
+			"v3": "extract error: keyword \"$dynamicRef\" not yet implemented (and 3 more errors)"
 		},
 		"tests": [
 			{

encoding/jsonschema/testdata/external/tests/draft2020-12/unevaluatedItems.json

@@ -1422,8 +1422,8 @@
 			"unevaluatedItems": false
 		},
 		"skip": {
-			"v2": "extract error: keyword \"prefixItems\" not yet implemented (and 1 more errors)",
-			"v3": "extract error: keyword \"prefixItems\" not yet implemented (and 1 more errors)"
+			"v2": "extract error: keyword \"unevaluatedItems\" not yet implemented",
+			"v3": "extract error: keyword \"unevaluatedItems\" not yet implemented"
 		},
 		"tests": [
 			{

encoding/jsonschema/testdata/txtar/ifthenelse.txtar

@@ -25,10 +25,10 @@
 }
 -- out/decode/extract --
 @jsonschema(schema="https://json-schema.org/draft/2019-09/schema")
-matchIf(null | bool | number | string | [...] | {
+matchIf({
 	a!: number
 	...
-}, null | bool | number | string | [...] | {
+}, {
 	b!: number
 	...
 }, _) & {