Match the asset's version the way the tag is parsed

AppUpdater.swift

@@ -755,13 +755,18 @@ struct Release: Decodable, Comparable {
         }
     }
 
+    /// The DMG named `<repo>-<version>.dmg` for this release. The version in
+    /// the name is parsed the way the tag is, so `MyApp-2.1.dmg` matches a
+    /// `v2.1` tag even though the tag prints as `2.1.0`.
     func viableAsset(forRepo repo: String) -> Asset? {
-        assets.first { asset in
-            let prefix = "\(repo.lowercased())-\(tagName)"
+        let prefix = "\(repo.lowercased())-"
+        return assets.first { asset in
             let name = (asset.name as NSString).deletingPathExtension
                 .lowercased()
-
-            return name == prefix && asset.contentType == .dmg
+            guard asset.contentType == .dmg, name.hasPrefix(prefix) else {
+                return false
+            }
+            return Version(tolerant: name.dropFirst(prefix.count)) == tagName
         }
     }
 

README.md

@@ -43,7 +43,8 @@ $ ditto "$SWIFT_BIN/AppUpdater_AppUpdater.bundle" \
 ## Release layout
 
 AppUpdater only accepts DMG assets. Name each asset
-`<repository>-<semantic-version>.dmg`, for example `MyApp-2.1.0.dmg`.
+`<repository>-<version>.dmg`, for example `MyApp-2.1.0.dmg`. The version is
+read the way the tag is, so a `v2.1` release may name its asset `MyApp-2.1.dmg`.
 
 The mounted DMG must contain one top-level app. Its filename must match the
 installed app, including case. A release for `MyApp.app` therefore contains:

Tests/AppUpdaterTests/AppUpdaterTests.swift

@@ -356,6 +356,46 @@ final class AppUpdaterTests: XCTestCase {
         }
     }
 
+    @MainActor
+    func testCheckMatchesAssetNamedWithShortVersion() async throws {
+        let releases = try [
+            release("v2.1", prerelease: false, assetName: "AppUpdater-2.1.dmg"),
+        ]
+        let updater = AppUpdater(
+            owner: "mxcl",
+            repo: "AppUpdater",
+            currentVersion: { Version(2, 0, 0) },
+            fetchReleases: { releases },
+            prepareAsset: { asset in preparedUpdate(assetName: asset.name) }
+        )
+
+        let update = try await updater.check()
+
+        XCTAssertEqual(update?.version, "2.1.0")
+        XCTAssertEqual(update?.assetName, "AppUpdater-2.1.dmg")
+    }
+
+    @MainActor
+    func testCheckDoesNotMatchAssetForAnotherVersion() async throws {
+        let releases = try [
+            release("v2.1", prerelease: false, assetName: "AppUpdater-2.1.1.dmg"),
+        ]
+        let updater = AppUpdater(
+            owner: "mxcl",
+            repo: "AppUpdater",
+            currentVersion: { Version(2, 0, 0) },
+            fetchReleases: { releases },
+            prepareAsset: { _ in
+                XCTFail("update should not run")
+                return preparedUpdate()
+            }
+        )
+
+        let update = try await updater.check()
+
+        XCTAssertNil(update)
+    }
+
     @MainActor
     func testCheckDoesNotUpdateWithoutMatchingAsset() async throws {
         let releases = try [
@@ -1447,7 +1487,9 @@ final class AppUpdaterTests: XCTestCase {
         }
         """.data(using: .utf8)!
 
-        return try JSONDecoder().decode(Release.self, from: json)
+        let decoder = JSONDecoder()
+        decoder.userInfo[.decodingMethod] = DecodingMethod.tolerant
+        return try decoder.decode(Release.self, from: json)
     }
 
     private func temporaryDirectory() throws -> URL {