Keep config mutability at top level

diff --git a/pinch.py b/pinch.py
index 58f7a3290cc507760303858cd90ba351f118d0e0..f5fbb481bea3cb0df30bf45f12c40d58dda55f83 100644 (file)
--- a/pinch.py
+++ b/pinch.py
@@ -22,8 +22,10 @@ from typing import (
     Dict,
     Iterable,
     List,
+    NamedTuple,
     NewType,
     Tuple,
+    Union,
 )
 
 # Use xdg module when it's less painful to have as a dependency
@@ -86,19 +88,38 @@ class ChannelTableEntry(types.SimpleNamespace):
     url: str
 
 
-class SearchPath(types.SimpleNamespace, ABC):
+class AliasPin(NamedTuple):
+    pass
+
+
+class GitPin(NamedTuple):
+    git_revision: str
     release_name: str
 
+
+class ChannelPin(NamedTuple):
+    git_revision: str
+    release_name: str
+    tarball_url: str
+    tarball_sha256: str
+
+
+Pin = Union[AliasPin, GitPin, ChannelPin]
+
+
+class SearchPath(types.SimpleNamespace, ABC):
+
     @abstractmethod
-    def pin(self, v: Verification, conf: configparser.SectionProxy) -> None:
+    def pin(self, v: Verification) -> Pin:
         pass
 
 
 class AliasSearchPath(SearchPath):
     alias_of: str
 
-    def pin(self, v: Verification, conf: configparser.SectionProxy) -> None:
+    def pin(self, v: Verification) -> AliasPin:
         assert not hasattr(self, 'git_repo')
+        return AliasPin()
 
 
 # (This lint-disable is for pylint bug https://github.com/PyCQA/pylint/issues/179
@@ -109,20 +130,19 @@ class TarrableSearchPath(SearchPath, ABC):  # pylint: disable=abstract-method
     forwarded_url: str
     git_ref: str
     git_repo: str
-    git_revision: str
     old_git_revision: str
     table: Dict[str, ChannelTableEntry]
 
 
 class GitSearchPath(TarrableSearchPath):
-    def pin(self, v: Verification, conf: configparser.SectionProxy) -> None:
+    def pin(self, v: Verification) -> GitPin:
         if hasattr(self, 'git_revision'):
             self.old_git_revision = self.git_revision
             del self.git_revision
 
         git_fetch(v, self)
-        conf['release_name'] = git_revision_name(v, self)
-        conf['git_revision'] = self.git_revision
+        return GitPin(release_name=git_revision_name(v, self),
+                      git_revision=self.git_revision)
 
     def fetch(self, v: Verification, section: str,
               conf: configparser.SectionProxy) -> str:
@@ -136,16 +156,17 @@ class GitSearchPath(TarrableSearchPath):
 
 
 class ChannelSearchPath(TarrableSearchPath):
-    def pin(self, v: Verification, conf: configparser.SectionProxy) -> None:
+    def pin(self, v: Verification) -> ChannelPin:
         if hasattr(self, 'git_revision'):
             self.old_git_revision = self.git_revision
             del self.git_revision
 
         pin_channel(v, self)
-        conf['release_name'] = self.release_name
-        conf['tarball_url'] = self.table['nixexprs.tar.xz'].absolute_url
-        conf['tarball_sha256'] = self.table['nixexprs.tar.xz'].digest
-        conf['git_revision'] = self.git_revision
+        return ChannelPin(
+            release_name=self.release_name,
+            tarball_url=self.table['nixexprs.tar.xz'].absolute_url,
+            tarball_sha256=self.table['nixexprs.tar.xz'].digest,
+            git_revision=self.git_revision)
 
     # Lint TODO: Put tarball_url and tarball_sha256 in ChannelSearchPath
     # pylint: disable=no-self-use
@@ -598,7 +619,7 @@ def pin(args: argparse.Namespace) -> None:
 
         sp = read_search_path(config[section])
 
-        sp.pin(v, config[section])
+        config[section].update(sp.pin(v)._asdict())
 
     with open(args.channels_file, 'w') as configfile:
         config.write(configfile)