t/moe/config.py

   1 #!/usr/bin/env python
   2
   3 import re
   4 import sys
   5
   6 key_pattern = re.compile("^[A-Za-z0-9_-]+$")
   7 ref_pattern = re.compile("^[A-Za-z0-9_-]+")
   8
   9 class MoeConfigInvalid(Exception):
  10     pass
  11
  12 class MoeConfigEvalErr(Exception):
  13     pass
  14
  15 class MoeConfig:
  16     """Moe configuration file. Should be immutable once a part of a stack."""
  17
  18     def __init__(self, file=None, name=None):
  19         self.vars = {}
  20         if file is not None:
  21             self.load(file)
  22         elif name is not None:
  23             self.name = name
  24             try:
  25                 file = open(name, "r")
  26             except IOError, err:
  27                 raise MoeConfigInvalid, "Cannot open configuration file %s: %s" % (name, err.strerror)
  28             else:
  29                 self.load(file)
  30
  31     def set(self, k, v):
  32         self.vars[k] = [("s", v)]
  33
  34     def parse_line(self, x):
  35         x = x.rstrip("\n").lstrip(" \t")
  36         if x=="" or x.startswith("#"):
  37             pass
  38         else:
  39             sep = x.find("=")
  40             if sep >= 0:
  41                 k = x[:sep]
  42                 v = x[sep+1:]
  43                 if k.endswith("+"):
  44                     k = k[:-1]
  45                     if not self.vars.has_key(k):
  46                         self.vars[k] = [("a","")];
  47                 else:
  48                     self.vars[k] = []
  49                 if not key_pattern.match(k):
  50                     raise MoeConfigInvalid, "Malformed name of configuration variable"
  51                 if v.startswith("'"):
  52                     v=v[1:]
  53                     if not v.endswith("'"):
  54                         raise MoeConfigInvalid, "Misquoted string"
  55                     self.vars[k].append(("s", v[:-1]))
  56                 elif v.startswith('"'):
  57                     v=v[1:]
  58                     if not v.endswith('"'):
  59                         raise MoeConfigInvalid, "Misquoted string"
  60                     self.parse_interpolated(self.vars[k], v[:-1])
  61                 else:
  62                     self.parse_interpolated(self.vars[k], v)
  63             else:
  64                 raise MoeConfigInvalid, "Parse error"
  65
  66     def load(self, file):
  67         lino = 0
  68         for x in file.readlines():
  69             lino += 1
  70             try:
  71                 self.parse_line(x)
  72             except MoeConfigInvalid, x:
  73                 msg = x.message + " at line " + str(lino)
  74                 if hasattr(self, "name"):
  75                     msg += " of " + self.name
  76                 raise MoeConfigInvalid, msg
  77
  78     def parse_interpolated(self, list, s):
  79         while s<>"":
  80             if s.startswith("$"):
  81                 s = s[1:]
  82                 if s.startswith("{"):
  83                     p = s.find("}")
  84                     if not p:
  85                         raise MoeConfigInvalid, "Unbalanced braces"
  86                     k, s = s[1:p], s[p+1:]
  87                     if not key_pattern.match(k):
  88                         raise MoeConfigInvalid, "Invalid variable name"
  89                 else:
  90                     m = ref_pattern.match(s)
  91                     if m:
  92                         k, s = s[:m.end()], s[m.end():]
  93                     else:
  94                         raise MoeConfigInvalid, "Invalid variable reference"
  95                 list.append(("i", k))
  96             else:
  97                 p = s.find("$")
  98                 if p < 0:
  99                     p = len(s)
 100                 list.append(("s", s[:p]))
 101                 s = s[p:]
 102
 103     def dump(self, file=sys.stdout):
 104         for k,v in self.vars.items():
 105             file.write(k)
 106             if len(v) > 0 and v[0][0] == "a":
 107                 file.write("+")
 108                 v = v[1:]
 109             file.write("=")
 110             for t,w in v:
 111                 if t == "s":
 112                     file.write("'" + w + "'")
 113                 elif t == "i":
 114                     file.write('"$' + w + '"')
 115             file.write("\n")
 116
 117 class MoeConfigStack:
 118     """Stack of configuration files."""
 119
 120     def __init__(self, base=None):
 121         ## FIXME: Do we need to duplicate the config files themselves?
 122         if base:
 123             self.stk = base.stk[:]
 124         else:
 125             self.stk = []
 126         self.in_progress = {}
 127         self.reset_cache()
 128
 129     def reset_cache(self):
 130         self.cache = {}
 131
 132     def push(self, cfg):
 133         self.stk.append(cfg)
 134         self.reset_cache()
 135
 136     def __getitem__(self, k):
 137         if self.cache.has_key(k):
 138             return self.cache[k]
 139         if self.in_progress.has_key(k):
 140             raise MoeConfigEvalErr, "Definition of $%s is recursive" % k;
 141         self.in_progress[k] = 1;
 142         v = self.do_get(k, len(self.stk)-1)
 143         del self.in_progress[k]
 144         ## FIXME: This is disabled, because the immutability invariant is broken!
 145         # self.cache[k] = v
 146         return v
 147
 148     def do_get(self, k, pos):
 149         while pos >= 0:
 150             cfg = self.stk[pos]
 151             if cfg.vars.has_key(k):
 152                 new = cfg.vars[k]
 153                 if new[0][0] == "a":
 154                     v = self.do_get(k, pos-1)
 155                 else:
 156                     v = ""
 157                 for op,arg in new:
 158                     if op == "s":
 159                         v = v + arg
 160                     elif op == "i":
 161                         v = v + self[arg]
 162                 return v
 163             pos -= 1
 164         return ""
 165
 166     def keys(self):
 167         seen = {}
 168         for cfg in self.stk:
 169             for k in cfg.vars.keys():
 170                 seen[k] = None
 171         return seen.keys()
 172
 173     def dump(self, file=sys.stdout):
 174         for k in sorted(self.keys()):
 175             v = self[k]
 176             file.write("%s=%s\n" % (k,v))
 177
 178     def dump_defs(self, file=sys.stdout):
 179         file.write("Configuration stack:\n")
 180         level = 0
 181         for cfg in self.stk:
 182             level += 1
 183             file.write("(level %d)\n" % level)
 184             cfg.dump(file)
 185         file.write("(end)\n")
 186
 187     def apply_overrides(self, prefix):
 188         newstk = []
 189         for cfg in self.stk:
 190             over = MoeConfig()
 191             changed = False
 192             for k in cfg.vars.keys():
 193                 if k.startswith(prefix):
 194                     over.vars[k[len(prefix):]] = cfg.vars[k]
 195                     changed = True
 196             if changed:
 197                 clean = MoeConfig()
 198                 for k in cfg.vars.keys():
 199                     if not k.startswith(prefix):
 200                         clean.vars[k] = cfg.vars[k]
 201                 newstk.append(clean)
 202                 newstk.append(over)
 203             else:
 204                 newstk.append(cfg)
 205         self.stk = newstk
 206         self.reset_cache()