Fix sym.dump to export the value_table into the {ENUMS} field of the (#481)

.sym file.
Refactor to remove the use of global variables "enum_dict" and "enums"

Add a test which checks that enums in the original .sym file and enums
which appear as values on a signal are exported to the .sym file.

Author: Seneda

Diff for: src/canmatrix/formats/sym.py

@@ -38,8 +38,6 @@
 import canmatrix.utils
 
 logger = logging.getLogger(__name__)
-enum_dict = {}  # type: typing.Dict[str, str]
-enums = "{ENUMS}\n"
 
 
 def default_float_factory(value):  # type: (typing.Any) -> decimal.Decimal
@@ -101,8 +99,6 @@ def format_float(f):  # type: (typing.Any) -> str
 
 
 def create_signal(db, signal):  # type: (canmatrix.CanMatrix, canmatrix.Signal) -> str
-    global enums
-    global enum_dict
     output = ""
     if sys.version_info > (3, 0):
         quote_name = not signal.name.isidentifier()
@@ -159,12 +155,7 @@ def create_signal(db, signal):  # type: (canmatrix.CanMatrix, canmatrix.Signal)
             val_tab_name = signal.name
 
         output += "/e:%s " % val_tab_name
-        if val_tab_name not in enum_dict:
-            enum_dict[val_tab_name] = "enum " + val_tab_name + "(" + ', '.join(
-                '%s="%s"' %
-                (key, val) for (
-                    key, val) in sorted(
-                    signal.values.items())) + ")"
+
 
     default = signal.initial_value  # type: ignore
     min_ok = signal.min is None or default >= signal.min
@@ -182,17 +173,31 @@ def create_signal(db, signal):  # type: (canmatrix.CanMatrix, canmatrix.Signal)
     output += "\n"
     return output
 
+def create_enum_from_signal_values(signal):
+    enum_dict = {}
+    if len(signal.values) > 0:
+        val_tab_name = signal.enumeration
+        if val_tab_name is None:
+            val_tab_name = signal.name
+
+        if val_tab_name not in enum_dict:
+            enum_dict[val_tab_name] = "enum " + val_tab_name + "(" + ', '.join(
+                '%s="%s"' %
+                (key, val) for (
+                    key, val) in sorted(
+                    signal.values.items())) + ")"
+    return enum_dict
 
 def dump(db, f, **options):  # type: (canmatrix.CanMatrix, typing.IO, **typing.Any) -> None
     """
     export canmatrix-object as .sym file (compatible to PEAK-Systems)
     """
-    global enum_dict
-    global enums
     sym_encoding = options.get('symExportEncoding', 'iso-8859-1')
     ignore_encoding_errors = options.get("ignoreExportEncodingErrors", "")
 
     enum_dict = {}
+    for enum_name, enum_values in db.value_tables.items():
+        enum_dict[enum_name] = "enum {}({})".format(enum_name, ', '.join('{}="{}"'.format(*items) for items in sorted(enum_values.items())))
     enums = "{ENUMS}\n"
 
     header = """\
@@ -308,6 +313,7 @@ def send_receive(for_frame):
                     output += "CycleTime=" + str(frame.effective_cycle_time) + "\n"
                 for signal in frame.signals:
                     output += create_signal(db, signal)
+                    enum_dict.update(create_enum_from_signal_values(signal))
                 output += "\n"
     enums += '\n'.join(sorted(enum_dict.values()))
     # write output file

Diff for: src/canmatrix/tests/test_sym.py

@@ -212,13 +212,49 @@ def test_enums_read(enum_str, enum_dict, enum_label):
 {{ENUMS}}
 {}
 '''.format(enum_str).encode('utf-8'),
-        )
+    )
 
         matrix = canmatrix.formats.sym.load(f)
         assert matrix.load_errors == [], "Failed to load canmatrix, when testing enum case : '{}'".format(enum_label)
         assert matrix.value_tables == enum_dict, "Enum not parsed correctly : '{}'".format(enum_label)
-        f_out = io.BytesIO()
-        canmatrix.formats.sym.dump(matrix, f_out)
+
+
+def test_enums_export():
+    f = io.BytesIO('''\
+FormatVersion=5.0 // Do not edit this line!
+Title="An Example Title"
+
+{ENUMS}
+enum Animal(0="Dog",1="Cat",2="Fox")
+
+{SENDRECEIVE}
+
+[Frame1]
+ID=000h
+DLC=8
+Var=Signal1 unsigned 0,16
+'''.encode('utf-8'),
+    )
+
+    matrix = canmatrix.formats.sym.load(f)
+    assert matrix.load_errors == [], "Failed to load canmatrix"
+
+    # Add an enum to Signal1
+    matrix.frame_by_name("Frame1").signal_by_name("Signal1").enumeration = "Plants"
+    matrix.frame_by_name("Frame1").signal_by_name("Signal1").values = {0: "Grass", 1: "Flower", 2: "Tree"}
+
+    # Export and reimport
+    f_out = io.BytesIO()
+    canmatrix.formats.sym.dump(matrix, f_out)
+    f_in = io.BytesIO(f_out.getvalue())
+    new_matrix = canmatrix.formats.sym.load(f_in)
+
+    # Check that Enums from Enums table exported and reimported correctly
+    assert new_matrix.value_tables["Animal"] == {0: "Dog", 1: "Cat", 2: "Fox"}
+
+    # Check that Enums from a Signal.Values property exported and reimported correctly
+    assert new_matrix.value_tables["Plants"] == {0: "Grass", 1: "Flower", 2: "Tree"}
+
 
 
 def test_types_read():