1. A computer-implemented method for displaying source code annotations, the method comprising: receiving input at a code editor executing at the computer, the code editor operable in an edit mode to allow text editing of the input, the input comprising source code, the source code comprising instructions for mapping of values from one or more fields of a data source to one or more fields of a data destination; displaying the source code as received and edited in the code editor; automatically executing the source code by: compiling the source code into object code; sending the object code to an interface engine for execution thereby causing the interface engine to receive one or more structured messages from the data source containing values for performing the mapping, and to extract and collect from the structured messages, for each instruction of the source code from which the object code was derived, values of the one or more fields of the data source referenced by that instruction; receiving the collected field values from the interface engine; and for each displayed instruction of the source code, displaying an annotation comprising the value of any field referenced by that instruction as collected for that instruction, without exiting the edit mode.
1. A computer-implemented method for displaying source code annotations, the method comprising: receiving input at a code editor executing at the computer, the code editor operable in an edit mode to allow text editing of the input, the input comprising source code, the source code comprising instructions for mapping of values from one or more fields of a data source to one or more fields of a data destination; displaying the source code as received and edited in the code editor; automatically executing the source code by: compiling the source code into object code; sending the object code to an interface engine for execution thereby causing the interface engine to receive one or more structured messages from the data source containing values for performing the mapping, and to extract and collect from the structured messages, for each instruction of the source code from which the object code was derived, values of the one or more fields of the data source referenced by that instruction; receiving the collected field values from the interface engine; and for each displayed instruction of the source code, displaying an annotation comprising the value of any field referenced by that instruction as collected for that instruction, without exiting the edit mode. 3. The method of claim 1 , wherein the displaying an annotation comprises displaying the annotation beside the corresponding instruction in the code editor.