polymorphic fetch()

[pinch] / pinch.py

diff --git a/pinch.py b/pinch.py
index 662b425286b87a8c1ac25ac7ee318e26ca2ee466..58f7a3290cc507760303858cd90ba351f118d0e0 100644 (file)
--- 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
@@ -111,19 +113,15 @@ class TarrableSearchPath(SearchPath):
     old_git_revision: str
     table: Dict[str, ChannelTableEntry]
 
+
+class GitSearchPath(TarrableSearchPath):
     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)
+        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,
@@ -133,15 +131,36 @@ 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, 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
+
+    # 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 +566,9 @@ 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: