encoding/jsonschema: schema version support

This adds some logic for understanding JSON schema versions
which will be used to trigger version-specific behavior
in subsequent CLs.

Signed-off-by: Roger Peppe <[email protected]>
Change-Id: I91c15cbe54454d4f22a88e5ad532bfa2d03ad6f1
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1199315
Reviewed-by: Daniel Martí <[email protected]>
TryBot-Result: CUEcueckoo <[email protected]>
Unity-Result: CUE porcuepine <[email protected]>

encoding/jsonschema/constraints.go

@@ -118,7 +118,20 @@ var constraints = []*constraint{
 	p0("$schema", func(n cue.Value, s *state) {
 		// Identifies this as a JSON schema and specifies its version.
 		// TODO: extract version.
-		s.jsonschema, _ = s.strValue(n)
+
+		s.schemaVersion = versionDraft07 // Reasonable default version.
+		str, ok := s.strValue(n)
+		if !ok {
+			// If there's no $schema value, use the default.
+			return
+		}
+		sv, err := parseSchemaVersion(str)
+		if err != nil {
+			s.errf(n, "invalid $schema URL %q: %v", str, err)
+			return
+		}
+		s.schemaVersionPresent = true
+		s.schemaVersion = sv
 	}),
 
 	p0("$id", func(n cue.Value, s *state) {

encoding/jsonschema/decode.go

@@ -117,8 +117,9 @@ func (d *decoder) schema(ref []ast.Label, v cue.Value) (a []ast.Decl) {
 	expr, state := root.schemaState(v, allTypes, nil, false)
 
 	tags := []string{}
-	if state.jsonschema != "" {
-		tags = append(tags, fmt.Sprintf("schema=%q", state.jsonschema))
+	if state.schemaVersionPresent {
+		// TODO use cue/literal.String
+		tags = append(tags, fmt.Sprintf("schema=%q", state.schemaVersion))
 	}
 
 	if name == nil {
@@ -334,9 +335,12 @@ type state struct {
 	deprecated   bool
 	exclusiveMin bool // For OpenAPI and legacy support.
 	exclusiveMax bool // For OpenAPI and legacy support.
-	jsonschema   string
-	id           *url.URL // base URI for $ref
-	idPos        token.Pos
+
+	schemaVersion        schemaVersion
+	schemaVersionPresent bool
+
+	id    *url.URL // base URI for $ref
+	idPos token.Pos
 
 	definitions []ast.Decl
 

encoding/jsonschema/decode_test.go

@@ -109,7 +109,6 @@ func TestDecode(t *testing.T) {
 
 func TestMapURL(t *testing.T) {
 	v := cuecontext.New().CompileString(`
-$schema: "xxx"
 type: "object"
 properties: x: $ref: "https://something.test/foo#/definitions/blah"
 `)
@@ -129,15 +128,13 @@ properties: x: $ref: "https://something.test/foo#/definitions/blah"
 	qt.Assert(t, qt.Equals(string(b), `
 import "other.test/something:blah"
 
-@jsonschema(schema="xxx")
 x?: blah.#blah
 ...
 `[1:]))
 }
 
 func TestMapURLErrors(t *testing.T) {
 	v := cuecontext.New().CompileString(`
-$schema: "xxx"
 type: "object"
 properties: {
 	x: $ref: "https://something.test/foo#/definitions/x"
@@ -151,9 +148,9 @@ properties: {
 	})
 	qt.Assert(t, qt.Equals(errors.Details(err, nil), `
 cannot determine import path from URL "https://something.test/foo": some error:
-    foo.cue:5:5
+    foo.cue:4:5
 cannot determine import path from URL "https://something.test/foo": some error:
-    foo.cue:6:5
+    foo.cue:5:5
 `[1:]))
 }
 

encoding/jsonschema/testdata/emptyobj.txtar

@@ -3,7 +3,7 @@
 // Issue #734
 -- github-workflow.json --
 {
-  "$schema": "http://json-schema.org/draft-07/schema",
+  "$schema": "http://json-schema.org/draft-07/schema#",
   "definitions": {
     "obj1": {
       "oneOf": [
@@ -23,7 +23,7 @@
   }
 }
 -- out/decode/cue --
-@jsonschema(schema="http://json-schema.org/draft-07/schema")
+@jsonschema(schema="http://json-schema.org/draft-07/schema#")
 _
 
 #obj1: null | {

encoding/jsonschema/testdata/unsupported.txtar

@@ -1,6 +1,6 @@
 -- unsupported.json --
 {
-  "$schema": "http://json-schema.org/draft-07/schema",
+  "$schema": "http://json-schema.org/draft-07/schema#",
   "definitions": {
     "ref": {
       "properties": {
@@ -35,7 +35,7 @@
 
 
 -- out/decode/cue --
-@jsonschema(schema="http://json-schema.org/draft-07/schema")
+@jsonschema(schema="http://json-schema.org/draft-07/schema#")
 _
 
 #ref: null | {

encoding/jsonschema/version.go

@@ -0,0 +1,32 @@
+package jsonschema
+
+import (
+	"fmt"
+)
+
+//go:generate go run golang.org/x/tools/cmd/stringer -type=schemaVersion -linecomment
+
+type schemaVersion int
+
+const (
+	versionUnknown schemaVersion = iota // unknown
+	versionDraft04                      // http://json-schema.org/draft-04/schema#
+	versionDraft05                      //	http://json-schema.org/draft-05/schema#
+	versionDraft06                      //	http://json-schema.org/draft-06/schema#
+	versionDraft07                      //	http://json-schema.org/draft-07/schema#
+	version2019_09                      // https://json-schema.org/draft/2019-09/schema
+	version2020_12                      // https://json-schema.org/draft/2020-12/schema
+
+	numVersions // unknown
+)
+
+func parseSchemaVersion(sv string) (schemaVersion, error) {
+	// If this linear search is ever a performance issue, we could
+	// build a map, but it doesn't seem worthwhile for now.
+	for i := schemaVersion(1); i < numVersions; i++ {
+		if sv == i.String() {
+			return i, nil
+		}
+	}
+	return 0, fmt.Errorf("$schema URI not recognized")
+}