Fixed lint issues and missing documentation

internal/config/config_test.go

@@ -34,10 +34,18 @@ func TestKeysRoundTrip(t *testing.T) {
 	}
 }
 
-// Every section has the full method set, and its Flatten keys (which use the
-// section's JSCK* constant) line up with its cfg tag in the parent.
+// sectionType is the Section interface type.
+var sectionType = reflect.TypeOf((*Section)(nil)).Elem()
+
+// Every section, including embedded ones, implements Section, and its
+// Flatten keys (which use the section's JSCK* constant) line up with its cfg
+// tag in the parent. Sections are found by walking JobSearchConfig, so a new
+// section is checked without being listed anywhere.
 func TestSections(t *testing.T) {
 	var conf JobSearchConfig
+	if !reflect.PointerTo(reflect.TypeOf(conf)).Implements(sectionType) {
+		t.Error("*JobSearchConfig does not implement Section")
+	}
 	all := conf.Flatten()
 	checkSections(t, all, "", reflect.ValueOf(&conf).Elem())
 }
@@ -49,11 +57,10 @@ func checkSections(t *testing.T, all map[string]any, prefix string, section refl
 		}
 		fv := section.FieldByIndex(f.index)
 		name := fv.Type().Name()
-		for _, m := range []string{"Map", "Flatten", "TypeOf", "ValueOf", "SetValue"} {
-			if !fv.Addr().MethodByName(m).IsValid() {
-				t.Errorf("%s is missing method %s", name, m)
-			}
+		if !fv.Addr().Type().Implements(sectionType) {
+			t.Errorf("*%s does not implement Section", name)
 		}
+		checkEmbedded(t, fv.Type())
 		if flatten := fv.MethodByName("Flatten"); flatten.IsValid() {
 			keys := flatten.Call(nil)[0].Interface().(map[string]any)
 			for k := range keys {
@@ -66,3 +73,19 @@ func checkSections(t *testing.T, all map[string]any, prefix string, section refl
 		checkSections(t, all, joinKey(prefix, f.key), fv)
 	}
 }
+
+// checkEmbedded checks that structs embedded in a section, such as
+// JobSearchConfigSource, implement Section too.
+func checkEmbedded(t *testing.T, section reflect.Type) {
+	for i := 0; i < section.NumField(); i++ {
+		sf := section.Field(i)
+		if !sf.Anonymous || sf.Type.Kind() != reflect.Struct {
+			continue
+		}
+		if !reflect.PointerTo(sf.Type).Implements(sectionType) {
+			t.Errorf("*%s (embedded in %s) does not implement Section",
+				sf.Type.Name(), section.Name())
+		}
+		checkEmbedded(t, sf.Type)
+	}
+}