fix(config): address jsonschema/v6 Go Fan review — Draft hint, errors.New, UnmarshalJSON precision

[Copilot]

Three quick-win improvements surfaced by the Go Fan module review of santhosh-tekuri/jsonschema/v6.

Changes

• Fix misleading Draft 7 error hint (validation_server.go): The compile-failure hint incorrectly said "Draft 7" when the compiler defaults to Draft 2020-12. Updated to "valid JSON Schema document (Draft 2020-12 or earlier)".

• Replace fmt.Errorf("%s", ...) with errors.New (validation_schema.go): No format verbs, no wrapping — errors.New(sb.String()) is the correct idiom.

• Use jsonschema.UnmarshalJSON in validateServerAgainstSchema (validation_server.go): Aligns the custom-schema validation path with the embedded-schema path, avoiding potential number-precision loss from encoding/json.Unmarshal on large integers or high-precision floats. serverMap is initialized before the type assertion to guarantee it is never nil.

// Before
if err := json.Unmarshal(serverJSON, &serverMap); err != nil { ... }

// After
serverObj, parseErr := jsonschema.UnmarshalJSON(bytes.NewReader(serverJSON))
if parseErr != nil { ... }
if obj, ok := serverObj.(map[string]interface{}); ok {
    serverMap = obj
} else {
    logValidation.Printf("unexpected: server config parsed to non-object type, using empty map for validation: name=%s", name)
}

The test for the unknown ErrorKind default path in TestFormatErrorContext already existed (kind.Not{} case), so no new test was needed.

[Copilot]

Pull request overview

Updates JSON Schema validation messaging and error construction while attempting precision-safe custom-schema parsing.

Changes:

• Corrects the supported JSON Schema draft hint.
• Uses errors.New for static error construction.
• Switches server validation parsing to jsonschema.UnmarshalJSON.

Show a summary per file

File	Description
internal/config/validation_server.go	Updates schema guidance and parsing behavior.
internal/config/validation_schema.go	Simplifies formatted error construction.

Review details

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• Files reviewed: 2/2 changed files
• Comments generated: 1
• Review effort level: Medium

[lpcox]

@copilot address review feedback

[Copilot]

@copilot address review feedback

Fixed in the latest commit. The root cause was in StdinServerConfig.UnmarshalJSON (config_stdin.go): it was using encoding/json.Unmarshal to build the allFields map, which decodes all numbers as float64 — losing precision for integers beyond 2^53. The merged AdditionalProperties then clobbered the precise values from jsonschema.UnmarshalJSON in the validation path.

Change: replaced the json.Unmarshal(data, &allFields) call with jsonschema.UnmarshalJSON(bytes.NewReader(data)), which uses decoder.UseNumber() internally. Numbers in AdditionalProperties are now stored as json.Number (exact string representation) instead of float64.

Regression test added in validate_server_against_schema_test.go (TestValidateServerAgainstSchema_LargeIntegerPrecision): it round-trips 9007199254740993 through UnmarshalJSON and validates it against a "const": 9007199254740993 schema — this test would have failed before the fix. The pre-existing coverage test in config_stdin_unmarshal_coverage_test.go was updated to assert json.Number("42") instead of float64(42).