encoding/jsonschema: use latest schema version by default

An upcoming change exposes the fact that we use non-draft-07 features in
schemas that don't declare their version. Using the latest schema
version by default seems like it's probably the right thing to do.

Also actually _use_ the `DefaultVersion` constant that we purported to
use already.

We should probably change all our schemas to use an explicit `$schema`
keyword so they don't need changing if we support a new version, but
that won't happen for a good while, so we're good for now.

Signed-off-by: Roger Peppe <[email protected]>
Change-Id: Ibb25421fdf3d26194920b221611570630019af45
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1202559
Reviewed-by: Daniel Martí <[email protected]>
Unity-Result: CUE porcuepine <[email protected]>
TryBot-Result: CUEcueckoo <[email protected]>

encoding/jsonschema/decode_test.go

@@ -75,6 +75,10 @@ func TestDecode(t *testing.T) {
 		}
 
 		if versStr, ok := t.Value("version"); ok {
+			// TODO most schemas have neither an explicit $schema or a #version
+			// tag, so when we update the default version, they could break.
+			// We should probably change most of the tests to use an explicit $schema
+			// field apart from when we're explicitly testing the default version logic.
 			if versStr == "openapi" {
 				// OpenAPI doesn't have a JSON Schema URI so it gets a special case.
 				cfg.DefaultVersion = jsonschema.VersionOpenAPI

encoding/jsonschema/jsonschema.go

@@ -49,7 +49,7 @@ func Extract(data cue.InstanceOrValue, cfg *Config) (f *ast.File, err error) {
 		cfg.MapURL = DefaultMapURL
 	}
 	if cfg.DefaultVersion == VersionUnknown {
-		cfg.DefaultVersion = VersionDraft7
+		cfg.DefaultVersion = DefaultVersion
 	}
 	if cfg.Strict {
 		cfg.StrictKeywords = true
@@ -69,7 +69,7 @@ func Extract(data cue.InstanceOrValue, cfg *Config) (f *ast.File, err error) {
 
 // DefaultVersion defines the default schema version used when
 // there is no $schema field and no explicit [Config.DefaultVersion].
-const DefaultVersion = VersionDraft7
+const DefaultVersion = VersionDraft2020_12
 
 // A Config configures a JSON Schema encoding or decoding.
 type Config struct {

encoding/jsonschema/testdata/txtar/list.txtar

@@ -1,4 +1,5 @@
 -- schema.yaml --
+$schema: http://json-schema.org/draft-07/schema#
 type: object
 
 properties:
@@ -43,6 +44,7 @@ additionalProperties: false
 -- out/decode/extract --
 import "list"
 
+@jsonschema(schema="http://json-schema.org/draft-07/schema#")
 foo?: [...string]
 tuple?: [string, int, 2]
 has?: list.MatchN(>=1, 3)
@@ -51,8 +53,8 @@ size?: list.UniqueItems() & list.MaxItems(9) & [_, _, _, ...]
 additional?: [int, int, ...string]
 -- out/decode/testerr/err-foo-not-string --
 foo.0: conflicting values true and string (mismatched types bool and string):
-    generated.cue:3:8
-    generated.cue:3:11
+    generated.cue:4:8
+    generated.cue:4:11
     test/err-foo-not-string.json:2:10
 -- test/empty.json --
 {}