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SCons / AutomaticHelpFromAliases

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From Gary Oberbunner's technique, I came up with the following wrapper functions. They can be used to build the help text automatically from all of your Alias() commands:

from SCons.Script.SConscript import SConsEnvironment

#-- ------------------
#-- jDataClass holds data for the helper functions
class jDataClass:
    mHelpText = {}
    mHelpTextHead = []
    mHelpTextTail = []
SConsEnvironment.jData = jDataClass()
#-- ------------------
#-- wraps Alias to put the alias name in the help text
def jAlias(self, aliasname, tgt, helptext=None):
   thealias = self.Alias(aliasname, tgt)
   lcaliasname = aliasname.lower()
   if helptext is None:
       if not self.jData.mHelpText.has_key(lcaliasname):
          self.jData.mHelpText[lcaliasname] = '???'
       self.jData.mHelpText[lcaliasname] = helptext
   return thealias
SConsEnvironment.jAlias = jAlias
#-- ------------------
#-- adds a line of text to the help heading
def jHelpHead(self, msg):
SConsEnvironment.jHelpHead = jHelpHead
#-- ------------------
#-- adds a line of text to the help footing
def jHelpFoot(self, msg):
SConsEnvironment.jHelpFoot = jHelpFoot
#-- ------------------
#-- generates the help
def jGenHelp(self):
   tmp = []
   keys = self.jData.mHelpText.keys()
   maxlen = 0
   for a in keys:
      if len(a) > maxlen: maxlen = len(a)
   for a in keys:
      s = ' %-*s : %s' % (maxlen, a, self.jData.mHelpText[a])
SConsEnvironment.jGenHelp = jGenHelp
#-- ------------------
#-- adds upper/lower case of alias names for a target
def jSetAliases(self, projname, tgt):
   self.jAlias(projname, tgt)
   self.jAlias(projname.lower(), tgt, "compile " + projname)
SConsEnvironment.jSetAliases = jSetAliases = Dev()

env = Environment()
env.jHelpHead("First line of Help...")
env.jHelpFoot("Last line of Help...")

#use jAlias like Alias() except that you can add an optional bit of help text to it
env.jAlias('prepare_downloads', prepalias, "prepare 'downloads' html page")

.... other stuff here ...

#--- this statement must be the last in the file

when you do scons -h you get the help for all of your aliases automatically:

scons: Reading SConscript files ...
**** Compiling in debug mode...
scons: done reading SConscript files.
First line of Help...
   prepare_downloads : prepare 'downloads' html page
Last line of Help...
Use scons -H for help about command-line options.


This is really useful, and I'd vote for such functionality being added to the core Alias function. However, what happens if kAlias is called twice for the same target, i.e. adding targets to an alias, but the second call doesn't have any help text. Doesn't it overwrite the existing help text?