I'm beginning to realise why I didn't do the `toString` overriding way
back when. Thankfully, now that all of our tests are in the same place,
this is actually not a terrible ordeal.
Since some sanitisers don't handle backslashes correctly, I updated the data-flow configuration to incorporate a flow state tracking whether or not backslashes have been eliminated or converted to forward slashes.
Adds support for extraction filters as defined in
https://peps.python.org/pep-0706/
and implemented in Python 3.12.
By my reading, setting the filter to `'data'` or `'tar'` is probably
safe, whereas `'fully_trusted'` or the default (which is the same as
`None`) is not.
For now, I have just added this modelling to the tarslip query. We could
also share it with the modelling of `shutil.unpack_archive` (which has also
gained a `filter` argument), but it was unclear to me where we should put
this modelling in that case. Perhaps the best solution would be to merge
the experimental `py/tarslip-extended` query into the existing query (in
which case the current location is perhaps not too bad).
This commit removes SSA nodes from the data flow graph. Specifically, for a definition and use such as
```python
x = expr
y = x + 2
```
we used to have flow from `expr` to an SSA variable representing x and from that SSA variable to the use of `x` in the definition of `y`. Now we instead have flow from `expr` to the control flow node for `x` at line 1 and from there to the control flow node for `x` at line 2.
Specific changes:
- `EssaNode` from the data flow layer no longer exists.
- Several glue steps between `EssaNode`s and `CfgNode`s have been deleted.
- Entry nodes are now admitted as `CfgNodes` in the data flow layer (they were filtered out before).
- Entry nodes now have a new `toString` taking into account that the module name may be ambigous.
- Some tests have been rewritten to accomodate the changes, but only `python/ql/test/experimental/dataflow/basic/maximalFlowsConfig.qll` should have semantic changes.
- Comments have been updated
- Test output has been updated, but apart from `python/ql/test/experimental/dataflow/basic/maximalFlows.expected` only `python/ql/test/experimental/dataflow/typetracking-summaries/summaries.py` should have a semantic change. This is a bonus fix, probably meaning that something was never connected up correctly.
