From a67cfec99a43c3a437aeab3257552c035ebab5bf Mon Sep 17 00:00:00 2001
From: Scott Worley <scottworley@scottworley.com>
Date: Sat, 13 Jun 2020 09:46:44 -0700
Subject: [PATCH 1/1] Polymorphic pin()

---
 pinch.py | 39 +++++++++++++++++++++------------------
 1 file changed, 21 insertions(+), 18 deletions(-)

diff --git a/pinch.py b/pinch.py
index b76c8da..a90ec3b 100644
--- a/pinch.py
+++ b/pinch.py
@@ -101,7 +101,9 @@ class AliasSearchPath(SearchPath):
         assert not hasattr(self, 'git_repo')
 
 
-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
@@ -111,21 +113,6 @@ class TarrableSearchPath(SearchPath):
     old_git_revision: str
     table: Dict[str, ChannelTableEntry]
 
-    def pin(self, v: Verification, conf: configparser.SectionProxy) -> None:
-        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
-
     def fetch(self, v: Verification, section: str,
               conf: configparser.SectionProxy) -> str:
         if 'git_repo' not in conf or 'release_name' not in conf:
@@ -143,11 +130,27 @@ class TarrableSearchPath(SearchPath):
 
 
 class GitSearchPath(TarrableSearchPath):
-    pass
+    def pin(self, v: Verification, conf: configparser.SectionProxy) -> None:
+        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
 
 
 class ChannelSearchPath(TarrableSearchPath):
-    pass
+    def pin(self, v: Verification, conf: configparser.SectionProxy) -> None:
+        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
 
 
 def compare(a: str, b: str) -> Tuple[List[str], List[str], List[str]]:
-- 
2.44.1