Keep config mutability at top level

[pinch] / pinch.py

diff --git a/pinch.py b/pinch.py
index 662b425286b87a8c1ac25ac7ee318e26ca2ee466..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
@@ -86,45 +88,61 @@ 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()
 
 
-class TarrableSearchPath(SearchPath):
+# (This lint-disable is for pylint bug https://github.com/PyCQA/pylint/issues/179
+# which is fixed in pylint 2.5.)
+class TarrableSearchPath(SearchPath, ABC):  # pylint: disable=abstract-method
     channel_html: bytes
     channel_url: str
     forwarded_url: str
     git_ref: str
     git_repo: str
-    git_revision: str
     old_git_revision: str
     table: Dict[str, ChannelTableEntry]
 
-    def pin(self, v: Verification, conf: configparser.SectionProxy) -> None:
+
+class GitSearchPath(TarrableSearchPath):
+    def pin(self, v: Verification) -> GitPin:
         if hasattr(self, 'git_revision'):
             self.old_git_revision = self.git_revision
             del self.git_revision
 
-        if 'channel_url' in conf:
-            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
-        else:
-            git_fetch(v, self)
-            conf['release_name'] = git_revision_name(v, self)
-        conf['git_revision'] = self.git_revision
+        git_fetch(v, self)
+        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:
@@ -133,15 +151,37 @@ class TarrableSearchPath(SearchPath):
                 'Cannot update unpinned channel "%s" (Run "pin" before "update")' %
                 section)
 
-        if 'channel_url' in conf:
-            return fetch_with_nix_prefetch_url(
-                v, conf['tarball_url'], Digest16(
-                    conf['tarball_sha256']))
-
         ensure_git_rev_available(v, self)
         return git_get_tarball(v, self)
 
 
+class ChannelSearchPath(TarrableSearchPath):
+    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)
+        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
+    def fetch(self, v: Verification, section: str,
+              conf: configparser.SectionProxy) -> str:
+        if 'git_repo' not in conf or 'release_name' not in conf:
+            raise Exception(
+                'Cannot update unpinned channel "%s" (Run "pin" before "update")' %
+                section)
+
+        return fetch_with_nix_prefetch_url(
+            v, conf['tarball_url'], Digest16(
+                conf['tarball_sha256']))
+
+
 def compare(a: str, b: str) -> Tuple[List[str], List[str], List[str]]:
 
     def throw(error: OSError) -> None:
@@ -547,7 +587,9 @@ def git_revision_name(v: Verification, channel: TarrableSearchPath) -> str:
 def read_search_path(conf: configparser.SectionProxy) -> SearchPath:
     if 'alias_of' in conf:
         return AliasSearchPath(**dict(conf.items()))
-    return TarrableSearchPath(**dict(conf.items()))
+    if 'channel_url' in conf:
+        return ChannelSearchPath(**dict(conf.items()))
+    return GitSearchPath(**dict(conf.items()))
 
 
 def read_config(filename: str) -> configparser.ConfigParser:
@@ -577,7 +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)