Define in-use-but-undefined ScriptDBSyntaxError

Subclassed SyntaxError to provide some useful info when this happens. It
was happening with unittest.nse because it wasn't part of any category.
Previously, this would crash Zenmap because ScriptDBSyntaxError was
undefined. Now it crashes because there's really a syntax error (fixed
in previous revision)

zenmap/zenmapCore/ScriptMetadata.py

@@ -132,6 +132,11 @@ from zenmapCore.Paths import Path
 from zenmapCore.UmitLogging import log
 
 
+class ScriptDBSyntaxError(SyntaxError):
+    """Exception raised when encountering a syntax error in the script.db"""
+    pass
+
+
 class ScriptDB (object):
     """Class responsible for parsing the script.db file, fetching script
     names and categories."""
@@ -144,21 +149,38 @@ class ScriptDB (object):
         self.unget_buf = ""
 
         self.f = open(script_db_path, "r")
+        self.lineno = 1
+        self.line = ""
         try:
             self.entries_list = self.parse()
         finally:
             self.f.close()
 
+    def syntax_error(self, message):
+        e = ScriptDBSyntaxError(message)
+        e.filename = self.f.name
+        e.lineno = self.lineno
+        e.offset = len(self.line)
+        e.text = self.line
+        return e
+
     def getchar(self):
+        c = None
         if self.unget_buf:
             c = self.unget_buf[-1]
             self.unget_buf = self.unget_buf[:-1]
-            return c
         else:
-            return self.f.read(1)
+            c = self.f.read(1)
+        if c == "\n":
+            self.lineno += 1
+            self.line = ""
+        else:
+            self.line += c
+        return c
 
     def unget(self, data):
         if data:
+            self.line = self.line[:-len(data)]
             self.unget_buf += data
 
     def parse(self):
@@ -199,7 +221,7 @@ class ScriptDB (object):
                     repl = None
                     c = self.getchar()
                     if not c:
-                        raise ScriptDBSyntaxError()
+                        raise self.syntax_error("Unexpected EOF")
                     if c.isdigit():
                         d1 = c
                         d2 = self.getchar()
@@ -207,7 +229,8 @@ class ScriptDB (object):
                         if d1 and d2 and d3:
                             n = int(d1 + d2 + d3)
                             if n > 255:
-                                raise ScriptDBSyntaxError()
+                                raise self.syntax_error(
+                                        "Character code >255")
                             repl = chr(n)
                         else:
                             self.unget(d3)
@@ -215,7 +238,7 @@ class ScriptDB (object):
                     if not repl:
                         repl = self.LUA_STRING_ESCAPES.get(c)
                     if not repl:
-                        raise ScriptDBSyntaxError()
+                        raise self.syntax_error("Unhandled string escape")
                     c = repl
                 string.append(c)
                 c = self.getchar()
@@ -223,13 +246,15 @@ class ScriptDB (object):
         elif c in "{},=":
             return ("delim", c)
         else:
-            raise ScriptDBSyntaxError()
+            raise self.syntax_error("Unknown token")
 
     def expect(self, tokens):
         for token in tokens:
             t = self.token()
             if t != token:
-                raise ScriptDBSyntaxError()
+                raise self.syntax_error(
+                        "Unexpected token '%s', expected '%s'" % (
+                            t[1], token[1]))
 
     def parse_entry(self):
         entry = {}
@@ -239,7 +264,7 @@ class ScriptDB (object):
         self.expect((("delim", "{"), ("ident", "filename"), ("delim", "=")))
         token = self.token()
         if not token or token[0] != "string":
-            raise ScriptDBSyntaxError()
+            raise self.syntax_error("Unexpected non-string token or EOF")
         entry["filename"] = token[1]
         self.expect((("delim", ","), ("ident", "categories"),
             ("delim", "="), ("delim", "{")))
@@ -256,12 +281,14 @@ class ScriptDB (object):
                 break
             token = self.token()
         if token != ("delim", "}"):
-            raise ScriptDBSyntaxError()
+            raise self.syntax_error(
+                    "Unexpected token '%s', expected '}'" % (token[1]))
         token = self.token()
         if token == ("delim", ","):
             token = self.token()
         if token != ("delim", "}"):
-            raise ScriptDBSyntaxError()
+            raise self.syntax_error(
+                    "Unexpected token '%s', expected '}'" % (token[1]))
         return entry
 
     def get_entries_list(self):
@@ -472,7 +499,8 @@ def get_script_entries(scripts_dir, nselib_dir):
     return entries
 
 if __name__ == '__main__':
-    for entry in get_script_entries():
+    import sys
+    for entry in get_script_entries(sys.argv[1], sys.argv[2]):
         print "*" * 75
         print "Filename:", entry.filename
         print "Categories:", entry.categories