introduce PsycSyntaxError and error messages

parse.nim

@@ -27,6 +27,8 @@ type
     cursor: int
     remainingPartLen: int
 
+  PsycSyntaxError = object of Exception
+
   Validator = proc(c: char): bool
 
 proc validateTrue(c: char): bool = true
@@ -41,10 +43,13 @@ proc getUntil(input: string, delimiters: openArray[char], packet: var PsycPacket
       result.complete = true
       if i > packet.cursor:
         result.value = input[packet.cursor .. i - 1]
+      else:
+        result.value = ""
       packet.cursor = i
       break
     if not validate(input[i]):
-      raise new(ValueError)
+      raise newException(PsycSyntaxError,
+                         "invalid character '" & input[i] & "' in " & $packet.state)
 
 proc parseKeyword(input: string,
                   packet: var PsycPacket): tuple[complete: bool, value: string] =
@@ -53,8 +58,8 @@ proc parseKeyword(input: string,
   result = input.getUntil([' ', '\t', '\n'], packet, validate)
   if result.complete:
     packet.cursor.inc()
-    if result.value.isNil() or result.value.len() == 0 or result.value[0] != '_':
-      raise new(ValueError) # name does not start with '_'
+    if result.value.len() == 0 or result.value[0] != '_':
+      raise newException(PsycSyntaxError, $packet.state & " does not start with '_'")
 
 proc parseModifierValueLength(input: string,
                               packet: var PsycPacket): tuple[complete: bool,
@@ -64,10 +69,13 @@ proc parseModifierValueLength(input: string,
     return (false, -1)
   packet.cursor.inc()
   if value.len() == 0:
-    raise new(ValueError) # no value length
-  result = (true, value.parseInt()) # may throw ValueError if invalid number
+    raise newException(PsycSyntaxError, "missing length after " & $packet.state)
+  try:
+    result = (true, value.parseInt()) # may throw ValueError if invalid number
+  except ValueError:
+    raise newException(PsycSyntaxError, "invalid length after " & $packet.state)
   if result.value < 0:
-    raise new(ValueError) # negative value length
+    raise newException(PsycSyntaxError, "invalid length after " & $packet.state)
 
 proc parseModifierName(input: string,
                        packet: var PsycPacket): tuple[complete: bool,
@@ -84,7 +92,8 @@ proc parseModifierName(input: string,
   packet.cursor.inc()
   if result.op == '?':
     if input[packet.cursor] != '\n':
-      raise new(ValueError) # '?' must be on a line by itself
+      raise newException(PsycSyntaxError,
+                         $packet.state & " has invalid operator '?'")
     result.complete = true
     return 
   (result.complete, result.name) = parseKeyword(input, packet)
@@ -96,7 +105,7 @@ proc parseModifierName(input: string,
     (result.complete, packet.remainingPartLen) = parseModifierValueLength(input,
                                                                           packet)
   elif input[packet.cursor - 1] != '\t':
-    raise new(ValueError) # invalid separator
+    raise newException(PsycSyntaxError, $packet.state & " has invalid separator")
  
 proc parseMethod(input: string, packet: var PsycPacket): tuple[complete: bool,
                                                                value: string] =
@@ -126,7 +135,8 @@ proc parseModifierValue(input: string,
   if result.complete:
     result.value = input[packet.cursor .. packet.cursor + packet.remainingPartLen - 1]
     if input[packet.cursor + packet.remainingPartLen] != '\n':
-      raise new(ValueError) # missing '\n' after binary-arg
+      raise newException(PsycSyntaxError,
+                         $packet.state & " is missing '\n' after binary-arg")
     packet.cursor += result.value.len() + 1
     packet.remainingPartLen = -1
   else:
@@ -144,9 +154,12 @@ proc parseContentLength(input: string,
     if value.len() == 0:
       result.value = -1
     else:
-      result.value = value.parseInt() # parseInt may throw ValueError if invalid number
+      try:
+        result.value = value.parseInt() # parseInt may throw ValueError if invalid number
+      except ValueError:
+        raise newException(PsycSyntaxError, "invalid length after " & $packet.state)
       if result.value < 0:
-        raise new(ValueError) # negative content length
+        raise newException(PsycSyntaxError, "invalid length after " & $packet.state)
 
 proc parseData(input: string,
                packet: var PsycPacket): tuple[complete: bool, value: string] =