Use type rather than field presence

[pinch] / pinch.py

diff --git a/pinch.py b/pinch.py
index 7049b69134f7ac114c58d815662c221817972c37..bfc6ac635dfd0866e8cae54d56ac4a9c1daae44f 100644 (file)
--- a/pinch.py
+++ b/pinch.py
@@ -1,3 +1,4 @@
+from abc import ABC, abstractmethod
 import argparse
 import configparser
 import filecmp
@@ -85,12 +86,22 @@ class ChannelTableEntry(types.SimpleNamespace):
     url: str
 
 
-class SearchPath(types.SimpleNamespace):
+class SearchPath(types.SimpleNamespace, ABC):
     release_name: str
 
+    @abstractmethod
+    def pin(self, v: Verification, conf: configparser.SectionProxy) -> None:
+        pass
 
-class Channel(SearchPath):
+
+class AliasSearchPath(SearchPath):
     alias_of: str
+
+    def pin(self, v: Verification, conf: configparser.SectionProxy) -> None:
+        assert not hasattr(self, 'git_repo')
+
+
+class Channel(SearchPath):
     channel_html: bytes
     channel_url: str
     forwarded_url: str
@@ -101,10 +112,6 @@ class Channel(SearchPath):
     table: Dict[str, ChannelTableEntry]
 
     def pin(self, v: Verification, conf: configparser.SectionProxy) -> None:
-        if hasattr(self, 'alias_of'):
-            assert not hasattr(self, 'git_repo')
-            return
-
         if hasattr(self, 'git_revision'):
             self.old_git_revision = self.git_revision
             del self.git_revision
@@ -528,6 +535,8 @@ def git_revision_name(v: Verification, channel: Channel) -> str:
 
 
 def read_search_path(conf: configparser.SectionProxy) -> SearchPath:
+    if 'alias_of' in conf:
+        return AliasSearchPath(**dict(conf.items()))
     return Channel(**dict(conf.items()))
 
 
@@ -537,6 +546,18 @@ def read_config(filename: str) -> configparser.ConfigParser:
     return config
 
 
+def read_config_files(
+        filenames: Iterable[str]) -> Dict[str, configparser.SectionProxy]:
+    merged_config: Dict[str, configparser.SectionProxy] = {}
+    for file in filenames:
+        config = read_config(file)
+        for section in config.sections():
+            if section in merged_config:
+                raise Exception('Duplicate channel "%s"' % section)
+            merged_config[section] = config[section]
+    return merged_config
+
+
 def pin(args: argparse.Namespace) -> None:
     v = Verification()
     config = read_config(args.channels_file)
@@ -554,28 +575,21 @@ def pin(args: argparse.Namespace) -> None:
 
 def update(args: argparse.Namespace) -> None:
     v = Verification()
-    config = configparser.ConfigParser()
     exprs: Dict[str, str] = {}
-    configs = [read_config(filename) for filename in args.channels_file]
-    for config in configs:
-        for section in config.sections():
-            if 'alias_of' in config[section]:
-                assert 'git_repo' not in config[section]
-                continue
-            sp = read_search_path(config[section])
-            tarball = sp.fetch(v, section, config[section])
-            if section in exprs:
-                raise Exception('Duplicate channel "%s"' % section)
-            exprs[section] = (
-                'f: f { name = "%s"; channelName = "%%s"; src = builtins.storePath "%s"; }' %
-                (config[section]['release_name'], tarball))
-
-    for config in configs:
-        for section in config.sections():
-            if 'alias_of' in config[section]:
-                if section in exprs:
-                    raise Exception('Duplicate channel "%s"' % section)
-                exprs[section] = exprs[str(config[section]['alias_of'])]
+    config = read_config_files(args.channels_file)
+    for section in config:
+        sp = read_search_path(config[section])
+        if isinstance(sp, AliasSearchPath):
+            assert 'git_repo' not in config[section]
+            continue
+        tarball = sp.fetch(v, section, config[section])
+        exprs[section] = (
+            'f: f { name = "%s"; channelName = "%%s"; src = builtins.storePath "%s"; }' %
+            (config[section]['release_name'], tarball))
+
+    for section in config:
+        if 'alias_of' in config[section]:
+            exprs[section] = exprs[str(config[section]['alias_of'])]
 
     command = [
         'nix-env',