setLevelForNamespace now instantiates the namespace if necessary

- Hide initLoggingNamespace. getLoggerForNamespace should be used
  instead.
- setLevelForNamespace now calls getLoggerForNamespace to ensure the
  namespace exists when a caller tries to set the logging level.
  Previously it was possible to call setLevelForNamespace before the
  namespace was initialized, meaning that the setting had no effect.
  This is especially problematic for cases where a library is using
  namespaced logging with the filter set to a high level by default.
  The code using that library may want to enable debug logs, and is
  likely to call setLevelForNamespace in initialization code that runs
  prior to the library code which instantiates the namespace.

namespaced_logging.nimble

@@ -1,6 +1,6 @@
 # Package
 
-version       = "0.2.0"
+version       = "0.3.0"
 author        = "Jonathan Bernard"
 description   = "Wrapper around std/logging to provide namespaced logging."
 license       = "MIT"

src/namespaced_logging.nim

@@ -1,6 +1,6 @@
-import logging, sequtils, strutils, tables
+import std/[logging, options, sequtils, strutils, tables]
 
-export logging.Level
+export logging
 
 type
   LoggingNamespace* = ref object
@@ -15,7 +15,7 @@ template knownNamespaces(): TableRef[string, LoggingNamespace] =
     knownNamespacesInst = newTable[string, LoggingNamespace]()
   knownNamespacesInst
 
-proc initLoggingNamespace*(name: string, level = lvlInfo, msgPrefix: string): LoggingNamespace =
+proc initLoggingNamespace(name: string, level = lvlInfo, msgPrefix: string): LoggingNamespace =
   result = LoggingNamespace(
     name: name,
     level: level,
@@ -23,19 +23,30 @@ proc initLoggingNamespace*(name: string, level = lvlInfo, msgPrefix: string): Lo
 
   knownNamespaces[name] = result
 
-proc initLoggingNamespace*(name: string, level = lvlInfo): LoggingNamespace =
+proc getLoggerForNamespace*(
-  return initLoggingNamespace(name, level, name & ": ")
+    namespace: string,
+    level = lvlInfo,
+    msgPrefix: Option[string] = none[string]()
+  ): LoggingNamespace =
+  ## Get a LogginNamesapce for the given namespace. The first time this is
+  ## called for a given name space a new logger will be created. In that case,
+  ## the optional `level` and `msgPrefix` will be used to configure the logger.
+  ## In all other cases, these paratmers are ignored and the existing namespace
+  ## instance is returned
 
-proc getLoggerForNamespace*(namespace: string, level = lvlInfo): LoggingNamespace =
   if knownNamespaces.hasKey(namespace): return knownNamespaces[namespace]
-  else: return initLoggingNamespace(namespace, level)
+  else:
+    if msgPrefix.isSome:
+      return initLoggingNamespace(namespace, level, msgPrefix.get)
+    else:
+      return initLoggingNamespace(namespace, level, namespace)
 
 proc setLevelForNamespace*(namespace: string, lvl: Level, recursive = false) =
   if recursive:
     for k, v in knownNamespaces.pairs:
       if k.startsWith(namespace):
         v.level = lvl
-  elif knownNamespaces.hasKey(namespace): knownNamespaces[namespace].level = lvl
+  else: getLoggerForNamespace(namespace).level = lvl
 
 proc name*(ns: LoggingNamespace): string = ns.name
 proc log*(ns: LoggingNamespace, level: Level, args: varargs[string, `$`]) =