i18n Python scripts: improve fg-copy-weather-scenarios-to-default-locale

- Use the new flightgear.meta.strutils.simplify() function.
- Automatically add a comment to the generated file to indicate that it
  was automatically generated and shouldn't be manually modified, etc.
- Improve error handling: abort with a clear error message if any of the
  'id', 'name' and 'desc' children of a 'scenario' element is
  problematic (empty or missing, for instance).
- Rename make_xml_leaf() to makeXmlLeaf() + other minor renaming.

python3-flightgear/fg-copy-weather-scenarios-to-default-locale

@@ -20,10 +20,12 @@
 import argparse
 import locale
 import os
-import sys
 import re
+import sys
+import textwrap
 import lxml.etree as ET
 
+import flightgear.meta.strutils as strutils
 from catalog import sgprops
 
 PROGNAME = os.path.basename(sys.argv[0])
@@ -50,34 +52,67 @@ Copy weather scenario descriptions to the default translation XML""",
 
     return parser.parse_args(namespace=params)
 
-# create an xml node with text content
-def make_xml_leaf(name, text):
+
+def insertInitialComment(root_elt, rel_input_path):
+    """Insert an XML comment before element 'root_elt'."""
+    s = textwrap.dedent("""\
+      This file was automatically generated from {input_file} using the
+      {progname} script from FGMeta. Modifications should be done either in
+      {input_file} or in that script.""".format(
+          progname=PROGNAME,
+          input_file=os.path.join("$FG_ROOT", rel_input_path)))
+    filled_paragraph = textwrap.fill(s, width=79)
+    comment_pseudo_element = ET.Comment(
+        " !!! Don't modify this file manually. !!!\n" + filled_paragraph + " ")
+    root_elt.addprevious(comment_pseudo_element)
+
+
+def stringifyChildValue(node, child):
+    # The 'or ""' is needed because an empty node is returned as None!
+    return strutils.simplify(node.getValue(child, "") or "")
+
+
+def makeXmlLeaf(name, text):
+    """Create an XML element with text contents."""
     leaf = ET.Element(name)
     leaf.text = '' if text is None else str(text)
     return leaf
 
-simplify_cre = re.compile(r"\s+")
-def simplifyString(input):
-    return simplify_cre.sub(" ", input.strip())
 
 def copyWeatherScenarios(fgdata):
-    environment_node = sgprops.readProps(os.path.join(fgdata, "Environment", "environment.xml"))
+    rel_input_path = os.path.join("Environment", "environment.xml")
+    environment_node = sgprops.readProps(os.path.join(fgdata, rel_input_path))
     scenarios = environment_node.getChild('weather-scenarios')
-    
-    result = ET.Element("PropertyList")
 
-    for s in scenarios.getChildren("scenario"):
-        scenarioId = s.getValue("id", None)
-        name = simplifyString(s.getValue("name", None))
-        desc = simplifyString(s.getValue("description", None))
+    root = ET.Element("PropertyList")
+    insertInitialComment(root, rel_input_path)
 
-        result.append(make_xml_leaf(scenarioId + "-name", name))
-        result.append(make_xml_leaf(scenarioId + "-desc", desc))
+    for scen_idx, scen_node in enumerate(scenarios.getChildren("scenario")):
+        scenarioId = scen_node.getValue("id", None)
+        if (not scenarioId) or scenarioId != strutils.simplify(scenarioId):
+            sys.exit(
+                "{prg}: 'scenario' element number {i} has a missing, empty "
+                "or suspiciously-formatted 'id' child; aborting.".format(
+                    prg=PROGNAME, i=scen_idx+1))
 
-    default_trans_file = os.path.join(fgdata, "Translations", "default", "weather-scenarios.xml")
+        name = stringifyChildValue(scen_node, "name")
+        desc = stringifyChildValue(scen_node, "description")
 
-    doc = ET.ElementTree(result)
-    doc.write(default_trans_file, encoding='utf-8', xml_declaration=True, pretty_print=True)
+        if not (name and desc):
+            sys.exit(
+                "{prg}: scenario '{scen}' has an empty or missing name or "
+                "description after string simplification; aborting.".format(
+                    prg=PROGNAME, scen=scenarioId))
+
+        root.append(makeXmlLeaf(scenarioId + "-name", name))
+        root.append(makeXmlLeaf(scenarioId + "-desc", desc))
+
+    default_trans_file = os.path.join(fgdata, "Translations", "default",
+                                      "weather-scenarios.xml")
+
+    doc = ET.ElementTree(root)
+    doc.write(default_trans_file, encoding='utf-8',
+              xml_declaration=True, pretty_print=True)
 
 
 def main():