pkg/encoding: add {yaml.json}.Validate

This allows creating types of embedded
YAML and JSON text that most conform
to the given CUE constraints.

Change-Id: I74e07f2f110251bd9c48feafd82b0a969a8ee2c1
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/2876
Reviewed-by: Marcel van Lohuizen <[email protected]>

Author: mpvl

cue/build.go

@@ -37,7 +37,16 @@ type Runtime struct {
 
 func init() {
 	internal.GetRuntime = func(instance interface{}) interface{} {
-		return &Runtime{idx: instance.(*Instance).index}
+		switch x := instance.(type) {
+		case Value:
+			return &Runtime{idx: x.idx}
+
+		case *Instance:
+			return &Runtime{idx: x.index}
+
+		default:
+			panic("argument must be Value or *Instance")
+		}
 	}
 
 	internal.CheckAndForkRuntime = func(runtime, value interface{}) interface{} {

cue/builtin_test.go

@@ -76,6 +76,18 @@ func TestBuiltins(t *testing.T) {
 	}, {
 		test("encoding/hex", `hex.Decode("foo")`),
 		`_|_(error in call to encoding/hex.Decode: encoding/hex: invalid byte: U+006F 'o')`,
+	}, {
+		test("encoding/json", `json.Validate("{\"a\":10}", {b:string})`),
+		`true`,
+	}, {
+		test("encoding/json", `json.Validate("{\"a\":10}", {a:<3})`),
+		`_|_(error in call to encoding/json.Validate: invalid value 10 (out of bound <3))`,
+	}, {
+		test("encoding/yaml", `yaml.Validate("a: 2\n---\na: 4", {a:<3})`),
+		`_|_(error in call to encoding/yaml.Validate: invalid value 4 (out of bound <3))`,
+	}, {
+		test("encoding/yaml", `yaml.Validate("a: 2\n---\na: 4", {a:<5})`),
+		`true`,
 	}, {
 		test("strconv", `strconv.FormatUint(64, 16)`),
 		`"40"`,

cue/builtins.go

@@ -0,0 +1,28 @@
+// Copyright 2019 CUE Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package yaml converts JSON to and from CUE.
+package json
+
+import (
+	"cuelang.org/go/cue"
+	"cuelang.org/go/pkg/encoding/json"
+)
+
+// Validate validates JSON and confirms it matches the constraints
+// specified by v.
+func Validate(b []byte, v cue.Value) error {
+	_, err := json.Validate(b, v)
+	return err
+}

encoding/json/json.go

@@ -23,6 +23,7 @@ import (
 	"cuelang.org/go/cue"
 	"cuelang.org/go/cue/ast"
 	"cuelang.org/go/internal/third_party/yaml"
+	pkgyaml "cuelang.org/go/pkg/encoding/yaml"
 	goyaml "github.com/ghodss/yaml"
 )
 
@@ -98,3 +99,10 @@ func EncodeStream(iter cue.Iterator) ([]byte, error) {
 	}
 	return buf.Bytes(), nil
 }
+
+// Validate validates the YAML and confirms it matches the constraints
+// specified by v. For YAML streams, all values must match v.
+func Validate(b []byte, v cue.Value) error {
+	_, err := pkgyaml.Validate(b, v)
+	return err
+}

encoding/yaml/yaml.go

@@ -22,6 +22,7 @@ import (
 	"cuelang.org/go/cue"
 	"cuelang.org/go/cue/ast"
 	"cuelang.org/go/cue/parser"
+	"cuelang.org/go/internal"
 )
 
 // Compact generates the JSON-encoded src with insignificant space characters
@@ -101,3 +102,22 @@ func Unmarshal(b []byte) (ast.Expr, error) {
 	}
 	return expr, nil
 }
+
+// Validate validates JSON and confirms it matches the constraints
+// specified by v.
+func Validate(b []byte, v cue.Value) (bool, error) {
+	if !json.Valid(b) {
+		return false, fmt.Errorf("json: invalid JSON")
+	}
+	r := internal.GetRuntime(v).(*cue.Runtime)
+	inst, err := r.Compile("json.Validate", b)
+	if err != nil {
+		return false, err
+	}
+
+	v = v.Unify(inst.Value())
+	if v.Err() != nil {
+		return false, v.Err()
+	}
+	return true, nil
+}

pkg/encoding/json/manual.go

@@ -16,9 +16,11 @@ package yaml
 
 import (
 	"bytes"
+	"io"
 
 	"cuelang.org/go/cue"
 	"cuelang.org/go/cue/ast"
+	"cuelang.org/go/internal"
 	"cuelang.org/go/internal/third_party/yaml"
 	goyaml "github.com/ghodss/yaml"
 )
@@ -54,3 +56,31 @@ func MarshalStream(v cue.Value) (string, error) {
 func Unmarshal(data []byte) (ast.Expr, error) {
 	return yaml.Unmarshal("", data)
 }
+
+// Validate validates YAML and confirms it matches the constraints
+// specified by v. If the YAML source is a stream, every object must match v.
+func Validate(b []byte, v cue.Value) (bool, error) {
+	d, err := yaml.NewDecoder("yaml.Validate", b)
+	if err != nil {
+		return false, err
+	}
+	r := internal.GetRuntime(v).(*cue.Runtime)
+	for {
+		expr, err := d.Decode()
+		if err != nil {
+			if err == io.EOF {
+				return true, nil
+			}
+			return false, err
+		}
+
+		inst, err := r.CompileExpr(expr)
+		if err != nil {
+			return false, err
+		}
+
+		if x := v.Unify(inst.Value()); x.Err() != nil {
+			return false, x.Err()
+		}
+	}
+}