[REEF-950] Make Tang allow empty string as a default value for String NameParameter

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.14
• Component/s: Tang
• Assignee: Dongjoon Hyun
• Reporter: Dongjoon Hyun
• Created: 16/Nov/15 14:03
• Updated: 17/Nov/15 07:56
• Resolved: 17/Nov/15 07:56

Description

Tang does not allow empty string, "", as a default value. Precisely speaking, we can declare it like the following, but it raises InjectionException if we use that as an `OptionalParameter`.

Sample.java

@NamedParameter(default_value = "")
class EmptyStringAsDefaultParam implements Name<String> {
}

It is because `NamedParameter` interface uses "" as a default value and `JavaNodeFactory` calls `isEmpty` to check the existence of default values.

NamedParameter.java

String default_value() default "";

JavaNodeFactory.java

if (!namedParameter.default_value().isEmpty()) {
...
}

Instead of Empty String, Tang had better use some kind of MAGIC String to distinguish whether the existence of default values.

Issue Links

• links to: Link to PR