#485 CFDataFile.putData destroys CFData instance on first write

[Rick Tanner]

This issue was discovered when using Claude to create a test system for Python based subsystems (message boards, citylife, banking, et al.)

Summary: CFDataFile.putData destroys CFData instance on first write, causing KeyError: '#' on any subsequent write through the same object

Component: crossfire-maps
File: python/CFDataFile.py
Function: CFDataFile.putData()
Severity: Major (data write silently corrupts in-memory state; second write crashes)

---

TL;DR Description:

CFDataFile.putData() mutates the dictionary it is given rather than working from a read-only view of it. This corrupts the calling CFData instance after the first write, making it impossible to perform a second write through the same object without a crash.

CFDataFile.putData() is always called with CFData.datadb as its argument:

self.datafile.putData(self.datadb)

Python passes dicts by reference, so inside putData the parameter dic and the instance variable self.datadb refer to the same object. The function reads the column header from the '#' key and then deletes it to avoid writing it as a data row:

header = dic['#']
del dic['#']           # <-- modifies self.datadb in-place
index = list(dic.keys())
index.sort()

After this runs, self.datadb no longer contains the '#' key. The write to disk completes correctly, but the in-memory object is permanently damaged. Any subsequent call to put_record(), remove_record(), or any other method that calls putData() will reach:

header = dic['#']      # KeyError: '#'

and crash.