Abort if existing PR targets newer version

src/Update.hs

@@ -44,10 +44,12 @@ import qualified Rewrite
 import qualified Skiplist
 import qualified Time
 import Utils
-  ( Options (..),
+  ( Boundary (..),
+    Options (..),
     URL,
     UpdateEnv (..),
     Version,
+    VersionMatcher (..),
     branchName,
     logDir,
     parseUpdates,
@@ -256,9 +258,11 @@ checkExistingUpdate log updateEnv existingCommitMsg attrPath = do
       lift $ log
         [interpolate|An auto update branch exists with message `$msg`. New version is $nV.|]
 
-      if U.titleTargetsSameVersion updateEnv msg
-      then throwError "An auto update branch exists targeting the same version"
-      else lift $ log "The auto update branch does not match the new version."
+      case U.titleVersion msg of
+        Just branchV | Version.matchVersion (RangeMatcher (Including nV) Unbounded) branchV ->
+          throwError "An auto update branch exists with an equal or greater version"
+        _ ->
+          lift $ log "The auto update branch does not match or exceed the new version."
 
   -- Note that this check looks for PRs with the same old and new
   -- version numbers, so it won't stop us from updating an existing PR

src/Utils.hs

@@ -23,7 +23,7 @@ module Utils
     runLog,
     srcOrMain,
     stripQuotes,
-    titleTargetsSameVersion,
+    titleVersion,
     whenBatch,
     regDirMode,
     outpathCacheDir,
@@ -135,10 +135,10 @@ prTitle updateEnv attrPath =
       nV = newVersion updateEnv
    in T.strip [interpolate| $attrPath: $oV -> $nV |]
 
-titleTargetsSameVersion :: UpdateEnv -> Text -> Bool
-titleTargetsSameVersion updateEnv = T.isSuffixOf [interpolate| -> $nV |]
+titleVersion :: Text -> Maybe Version
+titleVersion title = if T.null prefix then Nothing else Just suffix
   where
-    nV = newVersion updateEnv
+    (prefix, suffix) = T.breakOnEnd " -> " title
 
 regDirMode :: FileMode
 regDirMode =

test/UtilsSpec.hs

@@ -10,10 +10,20 @@ main = hspec spec
 
 spec :: Spec
 spec = do
+  let options = Utils.Options False False "" "" False False False False
+  let updateEnv = Utils.UpdateEnv "foobar" "1.0" "1.1" (Just "https://update-site.com") options
   describe "PR title" do
     -- This breaks IRC when it tries to link to newly opened pull requests
     it "should not include a trailing newline" do
-      let options = Utils.Options False False "" "" False False False False
-      let updateEnv = Utils.UpdateEnv "foobar" "1.0" "1.1" (Just "https://update-site.com") options
       let title = Utils.prTitle updateEnv "python37Packages.foobar"
       title `shouldBe` "python37Packages.foobar: 1.0 -> 1.1"
+
+  describe "titleVersion" do
+    it "should parse prTitle output" do
+      let title = Utils.prTitle updateEnv "python37Packages.foobar"
+      let version = Utils.titleVersion title
+      version `shouldBe` Just "1.1"
+
+    it "should fail on unexpected commit messages" do
+      let version = Utils.titleVersion "not a prTitle-style commit message"
+      version `shouldBe` Nothing