17. A computer-implemented method for autocompletion of variable references in source code, the method comprising: receiving input at a code editor executing at the computer, the input comprising source code and a search phrase, 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; triggering an autocompletion event for the search phrase; upon triggering the autocompletion event, executing the source code by compiling the source code into object code and sending the object code to an interface engine, to execute the object code at least until a breakpoint is reached causing the interface engine to receive one or more structured messages from the data source containing values for the mapping and to extract and collect, from the structured messages, values of each of the one or more fields of the data source; receiving the collected field values from the interface engine; generating a list of autocompletion suggestions for the search phrase, the list comprising variable identifiers whose corresponding collected field value contains the search phrase; presenting the list of autocompletion suggestions to a user in the code editor and enabling user selection of an autocompletion suggestion; and replacing the search phrase in the source code with a selected one of the autocompletion suggestions.
17. A computer-implemented method for autocompletion of variable references in source code, the method comprising: receiving input at a code editor executing at the computer, the input comprising source code and a search phrase, 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; triggering an autocompletion event for the search phrase; upon triggering the autocompletion event, executing the source code by compiling the source code into object code and sending the object code to an interface engine, to execute the object code at least until a breakpoint is reached causing the interface engine to receive one or more structured messages from the data source containing values for the mapping and to extract and collect, from the structured messages, values of each of the one or more fields of the data source; receiving the collected field values from the interface engine; generating a list of autocompletion suggestions for the search phrase, the list comprising variable identifiers whose corresponding collected field value contains the search phrase; presenting the list of autocompletion suggestions to a user in the code editor and enabling user selection of an autocompletion suggestion; and replacing the search phrase in the source code with a selected one of the autocompletion suggestions. 22. The method of claim 17 , wherein the data source is comprises an electronic data interchange document, the electronic data interface document being a DICOM header, an X12 document, an EDIFACT document, a JSON message, or a SWIFT transaction.