From 9363c380bdc7983b4d57f53bdcd0d8a0debed756 Mon Sep 17 00:00:00 2001
From: Travis Prescott <trpresco@microsoft.com>
Date: Tue, 4 Jun 2024 11:36:49 -0700
Subject: [PATCH] Add test case.

---
 packages/versioning/src/versioning.ts       | 32 +++++++++++++++++----
 packages/versioning/test/versioning.test.ts | 31 +++++++++++++++++++-
 2 files changed, 57 insertions(+), 6 deletions(-)

diff --git a/packages/versioning/src/versioning.ts b/packages/versioning/src/versioning.ts
index 78755ff279..892d85586f 100644
--- a/packages/versioning/src/versioning.ts
+++ b/packages/versioning/src/versioning.ts
@@ -212,7 +212,7 @@ function getParentAddedVersion(
       return versions.find((x) => x.name === key);
     }
   }
-  return undefined;
+  return versions[0];
 }
 
 function getParentAddedVersionInTimeline(
@@ -232,7 +232,16 @@ function getParentAddedVersionInTimeline(
       return moment.versions().next().value;
     }
   }
-  return undefined;
+  return timeline.first().versions().next().value;
+}
+
+/**
+ * Returns true if the first version modifier was @added, false if @removed.
+ */
+function resolveAddedFirst(added: Version[], removed: Version[]): boolean {
+  if (added.length === 0) return false;
+  if (removed.length === 0) return true;
+  return added[0].index < removed[0].index;
 }
 
 export function getAvailabilityMap(
@@ -261,9 +270,15 @@ export function getAvailabilityMap(
   )
     return undefined;
 
+  const wasAddedFirst = resolveAddedFirst(added, removed);
+
   // implicitly, all versioned things are assumed to have been added at
   // v1 if not specified, or inherited from their parent.
-  if (!added.length && !parentAdded) {
+  if (!wasAddedFirst && !parentAdded) {
+    // if the first version modifier was @removed, and the parent is implicitly available,
+    // then assume the type was available.
+    added = [allVersions[0], ...added];
+  } else if (!added.length && !parentAdded) {
     // no version information on the item or its parent implicitly means it has always been available
     added.push(allVersions[0]);
   } else if (!added.length && parentAdded) {
@@ -317,11 +332,18 @@ export function getAvailabilityMapInTimeline(
   )
     return undefined;
 
+  const wasAddedFirst = resolveAddedFirst(added, removed);
+
   // implicitly, all versioned things are assumed to have been added at
   // v1 if not specified, or inherited from their parent.
-  if (!added.length && !parentAdded) {
+  const firstVersion = timeline.first().versions().next().value;
+  if (!wasAddedFirst && !parentAdded) {
+    // if the first version modifier was @removed, and the parent is implicitly available,
+    // then assume the type was available.
+    added = [firstVersion, ...added];
+  } else if (!added.length && !parentAdded) {
     // no version information on the item or its parent implicitly means it has always been available
-    added.push(timeline.first().versions().next().value);
+    added.push(firstVersion);
   } else if (!added.length && parentAdded) {
     // if no version info on type but is on parent, inherit that parent's "added" version
     added.push(parentAdded);
diff --git a/packages/versioning/test/versioning.test.ts b/packages/versioning/test/versioning.test.ts
index 17cefbe3eb..e2635e891f 100644
--- a/packages/versioning/test/versioning.test.ts
+++ b/packages/versioning/test/versioning.test.ts
@@ -281,7 +281,7 @@ describe("versioning: logic", () => {
       );
     });
 
-    it("can be removed respecting model versioning", async () => {
+    it("can be removed respecting model versioning with explicit versions", async () => {
       const {
         source,
         projections: [v2, v3, v4],
@@ -311,6 +311,35 @@ describe("versioning: logic", () => {
       );
     });
 
+    it("can be removed respecting model versioning with implicit versions", async () => {
+      const {
+        source,
+        projections: [v1, v2, v3],
+      } = await versionedModel(
+        ["v1", "v2", "v3"],
+        `model Test {
+          a: int32;
+          @removed(Versions.v2)
+          @added(Versions.v3)
+          b: int32;
+        }
+        `
+      );
+
+      assertHasProperties(v1, ["a", "b"]);
+      assertHasProperties(v2, ["a"]);
+      assertHasProperties(v3, ["a", "b"]);
+
+      assertModelProjectsTo(
+        [
+          [v1, "v1"],
+          [v2, "v2"],
+          [v3, "v3"],
+        ],
+        source
+      );
+    });
+
     it("can be renamed", async () => {
       const {
         source,