juanfont/headscale · warning

marshaling expected online map: %w

Error message

marshaling expected online map: %w

What it means

json.MarshalIndent failed while serializing the expected online map built by integrationutil.BuildExpectedOnlineMap. Marshal only fails on unserializable Go values (channels, functions, cycles in the older encoder, +Inf/NaN floats, unsupported map key types). The expected map is built from parsed MapResponse data, so in practice this error is nearly unreachable — it would indicate a schema regression where an unsupported type leaked into the expected structure.

Source

Thrown at cmd/mapresponses/main.go:59

	command.RunOrFail(env, os.Args[1:])
}

// runIntegrationTest executes the integration test workflow.
func runOnline(env *command.Env) error {
	if mapConfig.Directory == "" {
		return errDirectoryRequired
	}

	resps, err := mapper.ReadMapResponsesFromDirectory(mapConfig.Directory)
	if err != nil {
		return fmt.Errorf("reading map responses from directory: %w", err)
	}

	expected := integrationutil.BuildExpectedOnlineMap(resps)

	out, err := json.MarshalIndent(expected, "", "  ")
	if err != nil {
		return fmt.Errorf("marshaling expected online map: %w", err)
	}

	os.Stderr.Write(out)
	os.Stderr.Write([]byte("\n"))

	return nil
}

View on GitHub (pinned to 565fd254d0)

Solutions

1. Treat it as a code defect: inspect what BuildExpectedOnlineMap produced (add a temporary debug print of the struct types)
2. Verify any newly added fields on the expected-map types are JSON-marshalable (no func/chan, json tags present)
3. If NaN floats can occur in captures, sanitize them to nil before building the expected map

out, err := json.MarshalIndent(expected, "", "  ")
if err != nil {
    // practically unreachable for plain structs; if hit, log the type that broke marshaling
    log.Printf("marshal failed: %v", err)
    return err
}

When it happens

Trigger: BuildExpectedOnlineMap output containing a func/chan field, a map with a non-string/comparable-but-unsupported key, or NaN/Inf float values produced by degenerate capture data.

Common situations: Practically never in normal operation; only after introducing new field types into the expected-map structs without json tags or with unsupported underlying types.

Related errors

• reading map responses from directory: %w
• failed to convert node interface
• type not supported
• invalid group member type
• group value must be an array of users

AI-assisted analysis of juanfont/headscale@565fd254d0 (2026-08-15). Data as JSON: /api/errors/0180e98ba2956186. Report an issue: GitHub.