encoding/jsonschema: unnecessary ellipses in open struct

[rogpeppe]

What version of CUE are you using (cue version)?

$ cue version
46fb300df650bbaefdbe70d646a1a5b45f968c1f

Does this issue reproduce with the latest stable release?

Yes (at least since v0.9.2)

What did you do?

exec cue def schema.json
cmp stdout want-stdout
-- schema.json --
{
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
        "a": {
            "oneOf": [
                {
                    "type": "object",
                    "properties": {
                        "a": {
                            "type": "boolean"
                        }
                    },
                    "required": [
                        "a"
                    ]
                },
                {
                    "type": "object",
                    "properties": {
                        "b": {
                            "type": "boolean"
                        }
                    },
                    "required": [
                        "b"
                    ]
                }
            ]
        }
    }
}
-- want-stdout --
@jsonschema(schema="https://json-schema.org/draft/2020-12/schema")
a?: matchN(1, [{
	a!: bool
}, {
	b!: bool
}])

What did you expect to see?

Passing test.

What did you see instead?

> exec cue def schema.json
[stdout]
@jsonschema(schema="https://json-schema.org/draft/2020-12/schema")
a?: {
	a: bool
	...
} | {
	b: bool
	...
}
...
> cmp stdout want-stdout
diff stdout want-stdout
--- stdout
+++ want-stdout
@@ -1,9 +1,6 @@
 @jsonschema(schema="https://json-schema.org/draft/2020-12/schema")
-a?: {
-	a: bool
-	...
-} | {
-	b: bool
-	...
-}
-...
+a?: matchN(1, [{
+	a!: bool
+}, {
+	b!: bool
+}])

FAIL: /tmp/y.txtar:2: stdout and want-stdout differ

The ellipses (...) are unecessary because the structs (and the top level package) are open anyway.