Auto-transfer infos

See the docstring for Component.create_connector for details on how it works.

I think this is a nice usability enhancement. The TimeTrigger component nicely shows how it can simplify the code for transferring metadata. Although it is still relatively complicated how the rules are constructed there, as the component is flexible regarding in which direction to transfer/where to take from. But all the complicated stuff in _connect is automated.

Fixes #73 (closed)

src/finam/tools/connect_helper.py

@@ -3,10 +3,15 @@ import logging
 
 from finam.interfaces import ComponentStatus, Loggable
 
+from ..data.tools import Info
 from ..errors import FinamNoDataError
 from ..tools.log_helper import ErrorLogger
 
 
+class MissingInfoError(Exception):
+    """Internal error type for handling missing infos for transfer rules"""
+
+
 class InfoSource:
     def __init__(self, name, *fields):
         self.name = name
@@ -71,9 +76,6 @@ class ConnectHelper(Loggable):
         self._outputs = outputs
         self._cache = cache
 
-        self._in_info_rules = in_info_rules or {}
-        self._out_info_rules = in_info_rules or {}
-
         with ErrorLogger(self.logger):
             for name in pull_data or []:
                 if name not in self._inputs:
@@ -93,12 +95,34 @@ class ConnectHelper(Loggable):
             name: False for name, out in self.outputs.items() if out.needs_push
         }
 
+        self._in_info_rules = in_info_rules or {}
+        self._out_info_rules = out_info_rules or {}
         self._check_info_rules()
 
         self._in_info_cache = {}
         self._out_info_cache = {}
         self._out_data_cache = {}
 
+    def _apply_rules(self, rules):
+        info = Info(time=None, grid=None)
+        for rule in rules:
+            if isinstance(rule, FromInput):
+                in_info = self.in_infos[rule.name]
+                if in_info is None:
+                    raise MissingInfoError()
+                for field in rule.fields:
+                    info.__setattr__(field, in_info.__getattr__(field))
+            elif isinstance(rule, FromOutput):
+                out_info = self.out_infos[rule.name]
+                if out_info is None:
+                    raise MissingInfoError()
+                for field in rule.fields:
+                    info.__setattr__(field, out_info.__getattr__(field))
+            elif isinstance(rule, FromValue):
+                info.__setattr__(field, rule.value)
+
+        return info
+
     def _check_info_rules(self):
         for name, rules in self._in_info_rules.items():
             if name not in self._inputs:
@@ -216,6 +240,22 @@ class ConnectHelper(Loggable):
         push_infos = {k: v for k, v in push_infos.items() if self.out_infos[k] is None}
         push_data = {k: v for k, v in push_data.items() if not self.data_pushed[k]}
 
+        for name, rules in self._in_info_rules.items():
+            if self.in_infos[name] is None and name not in self._in_info_cache:
+                try:
+                    info = self._apply_rules(rules)
+                    exchange_infos[name] = info
+                except MissingInfoError:
+                    pass
+
+        for name, rules in self._out_info_rules.items():
+            if self.out_infos[name] is None and name not in self._out_info_cache:
+                try:
+                    info = self._apply_rules(rules)
+                    push_infos[name] = info
+                except MissingInfoError:
+                    pass
+
         if self._cache:
             self._in_info_cache.update(exchange_infos)
             self._out_info_cache.update(push_infos)