Improve the error message for duplicate writes to help the user fix t…

…heir problem (#176 fixes #140)
diffplug · Jan 30, 2024 · 4f249ec · 4f249ec
2 parents 50d8286 + aa2a31d
commit 4f249ec
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diff --git a/jvm/CHANGELOG.md b/jvm/CHANGELOG.md
@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 ### Fixed
+- `@ParameterizedTest` no longer has. ([#140](https://github.com/diffplug/selfie/issues/140))
 - If a test class contained package-private methods and a single test method was run without the others, selfie would erroneously garbage collect disk snapshots for the other methods, now fixed. ([#175](https://github.com/diffplug/selfie/pull/175) fixes [#174](https://github.com/diffplug/selfie/issues/174))
 
 ## [1.1.1] - 2024-01-25

diff --git a/jvm/selfie-lib/src/commonMain/kotlin/com/diffplug/selfie/guts/WriteTracker.kt b/jvm/selfie-lib/src/commonMain/kotlin/com/diffplug/selfie/guts/WriteTracker.kt
@@ -50,21 +50,36 @@ class CallStack(val location: CallLocation, val restOfStack: List<CallLocation>)
 internal class FirstWrite<T>(val snapshot: T, val callStack: CallStack)
 
 /** For tracking the writes of disk snapshots literals. */
-open class WriteTracker<K : Comparable<K>, V> {
+sealed class WriteTracker<K : Comparable<K>, V> {
   internal val writes = mutableMapOf<K, FirstWrite<V>>()
   protected fun recordInternal(key: K, snapshot: V, call: CallStack, layout: SnapshotFileLayout) {
     val existing = writes[key]
     if (existing == null) {
       writes[key] = FirstWrite(snapshot, call)
     } else {
+      val howToFix =
+          when (this) {
+            is DiskWriteTracker ->
+                "You can fix this with `.toMatchDisk(String sub)` and pass a unique value for sub."
+            is InlineWriteTracker ->
+                """
+          You can fix this by doing an `if` before the assertion to separate the cases, e.g.
+            if (isWindows) {
+              expectSelfie(underTest).toBe("C:\\")
+            } else {
+              expectSelfie(underTest).toBe("bash$")
+            }
+        """
+                    .trimIndent()
+          }
       if (existing.snapshot != snapshot) {
         throw layout.fs.assertFailed(
-            "Snapshot was set to multiple values!\n  first time: ${existing.callStack.location.ideLink(layout)}\n   this time: ${call.location.ideLink(layout)}",
+            "Snapshot was set to multiple values!\n  first time: ${existing.callStack.location.ideLink(layout)}\n   this time: ${call.location.ideLink(layout)}\n$howToFix",
             existing.snapshot,
             snapshot)
       } else if (!layout.allowMultipleEquivalentWritesToOneLocation) {
         throw layout.fs.assertFailed(
-            "Snapshot was set to the same value multiple times.",
+            "Snapshot was set to the same value multiple times.\n$howToFix",
             existing.callStack.ideLink(layout),
             call.ideLink(layout))
       }