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jsonschema: marshal to bools #247

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Merged
merged 2 commits into from
Aug 6, 2025
Merged

jsonschema: marshal to bools #247

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597bbb7
jsonschema: marshal to bools
jba Aug 6, 2025
5994846
fix test #244
jba Aug 6, 2025
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15 changes: 14 additions & 1 deletion jsonschema/schema.go
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Original file line number Diff line number Diff line change
Expand Up @@ -204,6 +204,7 @@ func (s *Schema) MarshalJSON() ([]byte, error) {
if err := s.basicChecks(); err != nil {
return nil, err
}

// Marshal either Type or Types as "type".
var typ any
switch {
Expand All @@ -219,7 +220,19 @@ func (s *Schema) MarshalJSON() ([]byte, error) {
Type: typ,
schemaWithoutMethods: (*schemaWithoutMethods)(s),
}
return marshalStructWithMap(&ms, "Extra")
bs, err := marshalStructWithMap(&ms, "Extra")
if err != nil {
return nil, err
}
// Marshal {} as true and {"not": {}} as false.
// It is wasteful to do this here instead of earlier, but much easier.
switch {
case bytes.Equal(bs, []byte(`{}`)):
bs = []byte("true")
case bytes.Equal(bs, []byte(`{"not":true}`)):
bs = []byte("false")
}
return bs, nil
}

func (s *Schema) UnmarshalJSON(data []byte) error {
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6 changes: 3 additions & 3 deletions jsonschema/schema_test.go
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Expand Up @@ -54,9 +54,9 @@ func TestJSONRoundTrip(t *testing.T) {
for _, tt := range []struct {
in, want string
}{
{`true`, `{}`}, // boolean schemas become object schemas
{`false`, `{"not":{}}`},
{`{"type":"", "enum":null}`, `{}`}, // empty fields are omitted
{`true`, `true`},
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@findleyr findleyr Aug 6, 2025

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Do we want to make both of these changes, or just 'false'?
I've not seen many examples of a schema being 'true', but have seen examples of a schema being 'false'.

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@jba jba Aug 6, 2025

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It seems odd to do one without the other.

{`false`, `false`},
{`{"type":"", "enum":null}`, `true`}, // empty fields are omitted
{`{"minimum":1}`, `{"minimum":1}`},
{`{"minimum":1.0}`, `{"minimum":1}`}, // floating-point integers lose their fractional part
{`{"minLength":1.0}`, `{"minLength":1}`}, // some floats are unmarshaled into ints, but you can't tell
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4 changes: 1 addition & 3 deletions mcp/testdata/conformance/server/tools.txtar
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Expand Up @@ -59,9 +59,7 @@ greet
"type": "string"
}
},
"additionalProperties": {
"not": {}
}
"additionalProperties": false
},
"name": "greet"
}
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