half broken

internal/config/unknownkeys_test.go

@@ -0,0 +1,116 @@
+package config
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+// loadYAML writes body to a temp file and loads it, failing the test if Load
+// errors. Every test here wants "Load accepted this", so the helper asserts it
+// once instead of repeating the check.
+func loadYAML(t *testing.T, body string) *Config {
+	t.Helper()
+	path := filepath.Join(t.TempDir(), "config.yaml")
+	if err := os.WriteFile(path, []byte(body), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	cfg, err := Load(path)
+	if err != nil {
+		t.Fatalf("Load rejected the config: %v", err)
+	}
+	return cfg
+}
+
+// TestLoadIgnoresUnknownKeys pins a decision STATUS.md lists as open: Load
+// unmarshals leniently, so a key the struct does not know is silently dropped
+// instead of rejected. yaml.KnownFields(true) would catch it, and was
+// deliberately NOT adopted: it is a behaviour change for anyone carrying extra
+// keys in their config.
+//
+// The reason this is pinned rather than left alone is that leniency has already
+// cost this project twice (two test fixtures were caught by a stray key, not by
+// what they were testing). If the decision ever flips, the failure below is the
+// reminder to update STATUS.md, AGENTS.md and the README together.
+func TestLoadIgnoresUnknownKeys(t *testing.T) {
+	t.Run("a misspelled top-level block is dropped", func(t *testing.T) {
+		// The real trap from the field: the struct tag is "blocklist", so
+		// writing "block:" produces a plausible-looking server that has
+		// quietly kept every blocklist default. The correctly spelled
+		// block below disables the blocklist so the config validates at all
+		// — which is itself the sharper half of the pin: if the typo were
+		// honoured, block: {enabled: true} with no sources would fail
+		// Validate and the server would refuse to start.
+		cfg := loadYAML(t, `
+blocklist:
+  enabled: false
+block:
+  enabled: true
+  response_ip: 10.0.0.1
+  response_ttl: 5s
+`)
+		if cfg.Block.Enabled {
+			t.Fatal("the misspelled block: block was applied; Load is no longer lenient " +
+				"and this pin is stale")
+		}
+		if cfg.Block.ResponseIP != Default().Block.ResponseIP {
+			t.Fatalf("blocklist.response_ip = %q, want the default %q",
+				cfg.Block.ResponseIP, Default().Block.ResponseIP)
+		}
+	})
+
+	t.Run("the same block spelled correctly is applied", func(t *testing.T) {
+		// The control for the case above: the lenient path is the
+		// difference between these two keys, not Load ignoring the file.
+		cfg := loadYAML(t, `
+blocklist:
+  enabled: false
+  response_ip: 10.0.0.1
+  response_ttl: 5s
+`)
+		if cfg.Block.Enabled {
+			t.Fatal("blocklist.enabled: false was not applied")
+		}
+		if cfg.Block.ResponseIP != "10.0.0.1" {
+			t.Fatalf("blocklist.response_ip = %q, want 10.0.0.1", cfg.Block.ResponseIP)
+		}
+	})
+
+	t.Run("a misspelled nested key is dropped", func(t *testing.T) {
+		cfg := loadYAML(t, `
+blocklist:
+  enabled: false
+api:
+  basepath: /console
+`)
+		if cfg.API.BasePath != Default().API.BasePath {
+			t.Fatalf("api.base_path = %q, want the default %q — leniency changed",
+				cfg.API.BasePath, Default().API.BasePath)
+		}
+	})
+
+	t.Run("an unknown top-level key is dropped", func(t *testing.T) {
+		cfg := loadYAML(t, `
+blocklist:
+  enabled: false
+telemetry:
+  endpoint: https://example.invalid
+`)
+		if cfg.API.Enabled != Default().API.Enabled {
+			t.Fatalf("an unknown key changed the config: api.enabled = %v", cfg.API.Enabled)
+		}
+	})
+
+	t.Run("a known key with a bad TYPE is still fatal", func(t *testing.T) {
+		// The asymmetry is the point: a typo is invisible, a wrong value type
+		// is a startup failure. Leniency covers unknown keys only.
+		path := filepath.Join(t.TempDir(), "config.yaml")
+		if err := os.WriteFile(path, []byte("blocklist:\n  enabled: false\nserver:\n  max_concurrent: many\n"), 0o600); err != nil {
+			t.Fatal(err)
+		}
+		if _, err := Load(path); err == nil {
+			t.Fatal("Load accepted a string where a number belongs; the strictness " +
+				"contrast this pin documents is gone")
+		}
+	})
+}