Fix the invocation of function with gstring

modules/nextflow/src/main/groovy/nextflow/script/FunctionDef.groovy

@@ -16,7 +16,6 @@
 
 package nextflow.script
 
-import java.lang.reflect.Method
 
 import groovy.transform.CompileStatic
 /**
@@ -58,10 +57,22 @@ class FunctionDef extends ComponentDef implements ChainableDef {
         final meta = target.metaClass.getMetaMethod(name, arr)
         if( meta == null )
             throw new MissingMethodException(name, target.getClass(), arr)
-        Method callMethod = target.getClass().getMethod(name, meta.getNativeParameterTypes())
+        final types = meta.getNativeParameterTypes()
+        final callMethod = target.getClass().getMethod(name, types)
         if( callMethod == null )
             throw new MissingMethodException(name, target.getClass(), arr)
-        return callMethod.invoke(target, arr)
+        return callMethod.invoke(target, coerce0(arr,types))
+    }
+
+    static protected Object[] coerce0(Object[] arr, Class[] types) {
+        assert arr.length==types.length
+        // when the argument is a GString and type declared is a String
+        // force the evaluation of the string to invoke the target function
+        for( int i=0; i<arr.length; i++ ){
+            if( arr[i] instanceof GString && types[i]==String.class )
+                arr[i] = ((GString)arr[i]).toString()
+        }
+        return arr
     }
 
     @Override

modules/nextflow/src/test/groovy/nextflow/script/ScriptIncludesTest.groovy

@@ -1163,6 +1163,31 @@ class ScriptIncludesTest extends Dsl2Spec {
         def e = thrown(IllegalStateException)
         e.message == "Include statement is not allowed within a workflow definition"
 
+    }
+
+    def 'should should allow invoking function passing gstring' () {
+        given:
+        def folder = Files.createTempDirectory('test')
+        def MODULE = folder.resolve('module.nf')
+
+        MODULE.text = '''
+        def alpha(String str) {
+            return str.reverse()
+        }   
+        '''
 
+        when:
+        def SCRIPT = """
+        include { alpha } from "$MODULE"
+
+        def x = "world"
+        def y = "Hello \$x"
+
+        return alpha(y)
+        """
+        def runner = new MockScriptRunner()
+        def result = runner.setScript(SCRIPT).execute()
+        then:
+        result == 'dlrow olleH'
     }
 }