[GROOVY-4882] Concatenating an empty list to a GString throws a MethodSelectionException

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 1.7.5
• Fix Version/s: 1.8.2
• Assignee: Paul King
• Reporter: M. Justin
• Created: 14/Jun/11 17:33
• Updated: 31/Jan/12 23:04
• Resolved: 31/Jan/12 23:04

Description

A MethodSelectionException is thrown when appending an empty list to a GString that contains a ${} expression. Note that no exception is thrown if the GString does not contain a ${} expression or if the list is nonempty. The exception thrown is:

Caught: org.codehaus.groovy.runtime.metaclass.MethodSelectionException: Could not find which method plus() to invoke from this list:
  public groovy.lang.GString groovy.lang.GString#plus(groovy.lang.GString)
  public groovy.lang.GString groovy.lang.GString#plus(java.lang.String)

No other concatenation I've tried has this behavior. So the following line throws the exception:

"GString concat ${'a'}" + []

None of the following throw anything:

"GString concat ${'a'}" + ['abc']  // Concatenating a nonempty list
"GString concat " + []             // Concatenating an empty list, but not using ${} in the GString

// Concatenating various other object types
['abc', '', null, [:], 0, 1, false, new Object[0]].each { "GString concat ${'a'}" + it }

I would expect the behavior of appending an empty list to be consistent with appending any other list (or object type).