Draft: fix several issues with importAirfoilDAT.py

The importAirfoilDAT.py code could not handle several *.dat files posted in a forum topic.

src/Mod/Draft/importAirfoilDAT.py

@@ -9,7 +9,6 @@
 \brief Airfoil (.dat) file importer
 
 This module provides support for importing airfoil .dat files.
-Note (2019): this module has been unmaintained for a long time.
 '''
 # Check code with
 # flake8 --ignore=E226,E266,E401,W503
@@ -103,8 +102,9 @@ def open(filename):
     """
     docname = os.path.splitext(os.path.basename(filename))[0]
     doc = FreeCAD.newDocument(docname)
-    doc.Label = decodeName(docname[:-4])
-    process(doc, filename)
+    doc.Label = decodeName(docname)
+    process(filename)
+    doc.recompute()
 
 
 def insert(filename, docname):
@@ -131,13 +131,16 @@ def insert(filename, docname):
         doc = FreeCAD.getDocument(docname)
     except NameError:
         doc = FreeCAD.newDocument(docname)
-    importgroup = doc.addObject("App::DocumentObjectGroup", groupname)
-    importgroup.Label = decodeName(groupname)
-    process(doc, filename)
+    obj = process(filename)
+    if obj is not None:
+        importgroup = doc.addObject("App::DocumentObjectGroup", groupname)
+        importgroup.Label = decodeName(groupname)
+        importgroup.Group = [obj]
+    doc.recompute()
 
 
-def process(doc, filename):
-    """Process the filename and provide the document with the information.
+def process(filename):
+    """Process the filename and create a Draft Wire from the data.
 
     The common airfoil dat format has many flavors.
     This code should work with almost every dialect.
@@ -146,18 +149,15 @@ def process(doc, filename):
     ----------
     filename : str
         The path to the filename to be opened.
-    docname : str
-        The name of the active App::Document if one exists, or
-        of the new one created.
 
     Returns
     -------
-    App::Document
-        The active FreeCAD document, or the document created if none exists,
-        with the parsed information.
+    Part::Part2DObject or None.
+        The created Draft Wire object or None if the file contains less
+        than 3 points.
     """
     # Regex to identify data rows and throw away unused metadata
-    xval = r'(?P<xval>(\-|\d*)\.*\d*([Ee]\-?\d+)?)'
+    xval = r'(?P<xval>\-?\s*\d*\.*\d*([Ee]\-?\d+)?)'
     yval = r'(?P<yval>\-?\s*\d*\.*\d*([Ee]\-?\d+)?)'
     _regex = r'^\s*' + xval + r'\,?\s*' + yval + r'\s*$'
 
@@ -170,21 +170,28 @@ def process(doc, filename):
     # upside = True
     # last_x = None
 
-    # Collect the data for the upper and the lower side separately if possible
+    # Collect the data
     for lin in afile:
         curdat = regex.match(lin)
-        if curdat is not None:
+        if (curdat is not None
+                and curdat.group("xval")
+                and curdat.group("yval")):
             x = float(curdat.group("xval"))
             y = float(curdat.group("yval"))
 
-            # the normal processing
-            coords.append(Vector(x, y, 0))
+            # Some files specify the number of upper and lower points on the 2nd line:
+            # "       67.       72."
+            # See: http://airfoiltools.com/airfoil
+            # This line must be skipped:
+            if x < 2 and y < 2:
+                # the normal processing
+                coords.append(Vector(x, y, 0))
 
     afile.close()
 
     if len(coords) < 3:
         FCC.PrintError(translate("ImportAirfoilDAT", "Did not find enough coordinates") + "\n")
-        return
+        return None
 
     # sometimes coords are divided in upper an lower side
     # so that x-coordinate begin new from leading or trailing edge
@@ -227,4 +234,4 @@ def process(doc, filename):
         obj = FreeCAD.ActiveDocument.addObject('Part::Feature', airfoilname)
         obj.Shape = face
 
-    doc.recompute()
+    return obj