From 3d10ae393d01d9653aed77fbe0d46b0a472f1457 Mon Sep 17 00:00:00 2001
From: Aayush Thapa <aaythapa@amazon.com>
Date: Thu, 21 Mar 2024 15:57:08 -0700
Subject: [PATCH 1/3] add case for future arn generation

---
 samtranslator/translator/arn_generator.py | 26 +++++++++++++----------
 1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/samtranslator/translator/arn_generator.py b/samtranslator/translator/arn_generator.py
index a9f6e0325..d882206c9 100644
--- a/samtranslator/translator/arn_generator.py
+++ b/samtranslator/translator/arn_generator.py
@@ -18,17 +18,21 @@ def _region_to_partition(region: str) -> str:
     # setting default partition to aws, this will be overwritten by checking the region below
     region_string = region.lower()
     if region_string.startswith("cn-"):
-        return "aws-cn"
-    if region_string.startswith("us-iso-"):
-        return "aws-iso"
-    if region_string.startswith("us-isob"):
-        return "aws-iso-b"
-    if region_string.startswith("us-gov"):
-        return "aws-us-gov"
-    if region_string.startswith("eu-isoe"):
-        return "aws-iso-e"
-
-    return "aws"
+        partition = "aws-cn"
+    elif region_string.startswith("us-iso-"):
+        partition = "aws-iso"
+    elif region_string.startswith("us-isob"):
+        partition = "aws-iso-b"
+    elif region_string.startswith("us-gov"):
+        partition = "aws-us-gov"
+    elif region_string.startswith("eu-isoe"):
+        partition = "aws-iso-e"
+    elif "iso" in region_string:
+        partition = "{AWS::Partition}"
+    else:
+        partition = "aws"
+
+    return partition
 
 
 class ArnGenerator:

From 30bd5ed9594de93db679e64e80dfec6df5ca59ad Mon Sep 17 00:00:00 2001
From: Aayush Thapa <aaythapa@amazon.com>
Date: Tue, 26 Mar 2024 10:36:39 -0700
Subject: [PATCH 2/3] add tests + replace ifs

---
 samtranslator/translator/arn_generator.py | 31 +++++++++++------------
 tests/translator/test_arn_generator.py    | 10 +++++++-
 2 files changed, 24 insertions(+), 17 deletions(-)

diff --git a/samtranslator/translator/arn_generator.py b/samtranslator/translator/arn_generator.py
index d882206c9..733bae0eb 100644
--- a/samtranslator/translator/arn_generator.py
+++ b/samtranslator/translator/arn_generator.py
@@ -17,22 +17,21 @@ def _get_region_from_session() -> str:
 def _region_to_partition(region: str) -> str:
     # setting default partition to aws, this will be overwritten by checking the region below
     region_string = region.lower()
-    if region_string.startswith("cn-"):
-        partition = "aws-cn"
-    elif region_string.startswith("us-iso-"):
-        partition = "aws-iso"
-    elif region_string.startswith("us-isob"):
-        partition = "aws-iso-b"
-    elif region_string.startswith("us-gov"):
-        partition = "aws-us-gov"
-    elif region_string.startswith("eu-isoe"):
-        partition = "aws-iso-e"
-    elif "iso" in region_string:
-        partition = "{AWS::Partition}"
-    else:
-        partition = "aws"
-
-    return partition
+    region_to_partition_map = {
+        "cn-": "aws-cn",
+        "us-iso-": "aws-iso",
+        "us-isob": "aws-iso-b",
+        "us-gov": "aws-us-gov",
+        "eu-isoe": "aws-iso-e",
+    }
+    for key, value in region_to_partition_map.items():
+        if region_string.startswith(key):
+            return value
+
+    if "iso" in region_string:
+        return "${AWS::Partition}"
+
+    return "aws"
 
 
 class ArnGenerator:
diff --git a/tests/translator/test_arn_generator.py b/tests/translator/test_arn_generator.py
index ae2c1bf7f..d7187ccea 100644
--- a/tests/translator/test_arn_generator.py
+++ b/tests/translator/test_arn_generator.py
@@ -10,7 +10,15 @@ def setUp(self):
         ArnGenerator.BOTO_SESSION_REGION_NAME = None
 
     @parameterized.expand(
-        [("us-east-1", "aws"), ("cn-east-1", "aws-cn"), ("us-gov-west-1", "aws-us-gov"), ("US-EAST-1", "aws")]
+        [
+            ("us-east-1", "aws"),
+            ("cn-east-1", "aws-cn"),
+            ("us-gov-west-1", "aws-us-gov"),
+            ("us-isob-east-1", "aws-iso-b"),
+            ("eu-isoe-west-1", "aws-iso-e"),
+            ("US-EAST-1", "aws"),
+            ("us-isof-east-1", "${AWS::Partition}"),
+        ]
     )
     def test_get_partition_name(self, region, expected):
         actual = ArnGenerator.get_partition_name(region)

From e562e1892aff9d314d33d16033ce0ef5cc949d0b Mon Sep 17 00:00:00 2001
From: Aayush Thapa <aaythapa@amazon.com>
Date: Tue, 26 Mar 2024 10:47:21 -0700
Subject: [PATCH 3/3] add comment

---
 samtranslator/translator/arn_generator.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/samtranslator/translator/arn_generator.py b/samtranslator/translator/arn_generator.py
index 733bae0eb..852c66c74 100644
--- a/samtranslator/translator/arn_generator.py
+++ b/samtranslator/translator/arn_generator.py
@@ -28,6 +28,7 @@ def _region_to_partition(region: str) -> str:
         if region_string.startswith(key):
             return value
 
+    # Using the ${AWS::Partition} placeholder so that we don't have to add new regions to the static list above
     if "iso" in region_string:
         return "${AWS::Partition}"