Conflicts with existing generated files

[treiher]

Using the same target directory for code generation for different specifications (or variants of a specification without clean up between two consecutive runs) can lead to conflicts, which just get visible during compilation. We should consider showing a warning or even abort when there are already files in the target directory.

[jklmnn]

I just noticed the changes introduced with #1197 make make generate fail as it tries to generate multiple different packages into the same directory but then fails because common files like rflx-rflx_arithmetic.ads already exist:

make generate                     
tools/generate_spark_test_code.py
Parsing tests/data/specs/ethernet.rflx
Parsing tests/data/specs/in_ethernet.rflx
Parsing tests/data/specs/ipv4.rflx
Parsing tests/data/specs/in_ipv4.rflx
Parsing tests/data/specs/udp.rflx
Parsing tests/data/specs/icmp.rflx
Parsing tests/data/specs/ipv4.rflx
Parsing tests/data/specs/udp.rflx
Processing ICMP
Processing UDP
Processing IPv4
Processing Ethernet
Processing In_IPv4
Processing In_Ethernet
Generating ICMP::Tag
...
Creating tests/spark/generated/rflx-rflx_arithmetic.adb
Creating tests/spark/generated/rflx-rflx_generic_types-generic_operations.adb
Creating tests/spark/generated/rflx-rflx_message_sequence.adb
Creating tests/spark/generated/rflx-rflx_scalar_sequence.adb
Creating tests/spark/generated/rflx.ads
Generating TLV::Tag
Generating TLV::Length
Generating Derivation::Message
Creating tests/spark/generated/rflx-tlv.ads
Creating tests/spark/generated/rflx-derivation.ads
Creating tests/spark/generated/rflx-derivation-message.ads
Creating tests/spark/generated/rflx-derivation-message.adb
Creating tests/spark/generated/rflx-rflx_arithmetic.ads
Traceback (most recent call last):
  File "/.../RecordFlux/tools/generate_spark_test_code.py", line 75, in <module>
    sys.exit(main())
  File "/.../RecordFlux/tools/generate_spark_test_code.py", line 43, in main
    Generator(
  File "/.../RecordFlux/rflx/generator/generator.py", line 143, in generate
    self._write_files(units, directory, library_files, top_level_package)
  File "/.../RecordFlux/rflx/generator/generator.py", line 154, in _write_files
    self._write_library_files(directory)
  File "/.../RecordFlux/rflx/generator/generator.py", line 166, in _write_library_files
    create_file(
  File "/.../RecordFlux/rflx/generator/generator.py", line 1471, in create_file
    fail(f"file {filename} already exists", subsystem=Subsystem.GENERATOR)
  File "/.../RecordFlux/rflx/error.py", line 189, in fail
    _fail(RecordFluxError(), message, subsystem, severity, location)
  File "/.../RecordFlux/rflx/error.py", line 209, in _fail
    error.propagate()
  File "/.../RecordFlux/rflx/error.py", line 162, in propagate
    raise self
rflx.error.RecordFluxError: generator: error: file tests/spark/generated/rflx-rflx_arithmetic.ads already exists
make: *** [Makefile:162: generate] Error 1

[treiher]

Also, some tests are failing on main (and thus all rebased PRs) now:

=========================== short test summary info ============================
FAILED tests/integration/specification_model_generator_test.py::test_definite_message_with_builtin_type
FAILED tests/integration/specification_model_generator_test.py::test_definite_parameterized_message
FAILED tests/integration/specification_model_generator_test.py::test_parameterized_message
============= 3 failed, 23 passed, 8 skipped in 229.52s (0:03:49) ==============

This wasn't detected by the CI, because the verification tests were skipped.