More fixes for configs

Previously something like:

RETRIES = config_expr("settings").retry

class MyFlow(FlowSpec):
  @retries(times=RETRIES)
  @step
  def start(self):
    ...

  @retries(times=RETRIES)
  @step
  def end(self):
    ...

would fail. Also, something like:

FOO = config_expr("settings").foo.bar
BAR = FOO.BAZ
BLAH = FOO.BAZ2

would also fail.

This fixes these issues by copying DelayEvaluator everytime and also
making the `__call__` function reentrant.

Author: romain-intel

metaflow/user_configs/config_parameters.py

@@ -377,7 +377,7 @@ def __call__(self, ctx=None, deploy_time=False):
         # Evaluate the expression setting the config values as local variables
         try:
             return eval(
-                self._config_expr,
+                to_eval_expr,
                 self._globals or globals(),
                 {
                     k: ConfigValue(v)
@@ -387,7 +387,7 @@ def __call__(self, ctx=None, deploy_time=False):
         except NameError as e:
             raise MetaflowException(
                 "Config expression '%s' could not be evaluated: %s"
-                % (self._config_expr, str(e))
+                % (to_eval_expr, str(e))
             ) from e