From b78c35cc2b1ffddcb610f26ed774a5176d467a62 Mon Sep 17 00:00:00 2001
From: David Glick <david@glicksoftware.com>
Date: Sat, 9 Jul 2022 20:55:33 -0700
Subject: [PATCH] Make sure get_or_generate stores scales with the same uid

---
 news/60.bugfix                    |  5 +++++
 plone/scale/storage.py            |  7 ++++---
 plone/scale/tests/test_storage.py | 13 +++++++++++++
 3 files changed, 22 insertions(+), 3 deletions(-)
 create mode 100644 news/60.bugfix

diff --git a/news/60.bugfix b/news/60.bugfix
new file mode 100644
index 0000000..c8324e9
--- /dev/null
+++ b/news/60.bugfix
@@ -0,0 +1,5 @@
+* Fix to ensure that when a scale that was registered using `pre_scale` is
+  later actually generated by `get_or_generate`, it is stored with the same
+  uid as the placeholder info that was stored by `pre_scale`. This avoids
+  an issue where the same scale was generated repeatedly.
+  [davisagli]
diff --git a/plone/scale/storage.py b/plone/scale/storage.py
index 60bf8a3..fd3fca0 100644
--- a/plone/scale/storage.py
+++ b/plone/scale/storage.py
@@ -267,7 +267,7 @@ def pre_scale(self, **parameters):
         logger.debug(f"Pre scale returns new {info}")
         return info
 
-    def generate_scale(self, **parameters):
+    def generate_scale(self, uid=None, **parameters):
         logger.debug("Generating scale...")
         scaling_factory = IImageScaleFactory(self.context, None)
         if scaling_factory is None:
@@ -282,7 +282,8 @@ def generate_scale(self, **parameters):
         self._cleanup(fieldname=fieldname)
         data, format_, dimensions = result
         width, height = dimensions
-        uid = self.hash_key(**parameters)
+        if uid is None:
+            uid = self.hash_key(**parameters)
         key = self.hash(**parameters)
         info = dict(
             uid=uid,
@@ -331,7 +332,7 @@ def get_or_generate(self, name):
         # This scale has not been generated yet.
         # Get the parameters used when pre-registering this scale.
         parameters = self.unhash(info["key"])
-        return self.generate_scale(**parameters)
+        return self.generate_scale(uid=name, **parameters)
 
     def _cleanup(self, fieldname=None):
         storage = self.storage
diff --git a/plone/scale/tests/test_storage.py b/plone/scale/tests/test_storage.py
index 9ac541e..4456878 100644
--- a/plone/scale/tests/test_storage.py
+++ b/plone/scale/tests/test_storage.py
@@ -152,6 +152,19 @@ def test_get_or_generate(self):
         self.assertEqual(real["height"], 23)
         self.assertEqual(real["mimetype"], "image/png")
 
+    def test_get_or_generate__stable_uid(self):
+        # When get_or_generate actually generates the scale,
+        # it should store it with the same uid that was used
+        # to find the placeholder info, even if the field
+        # has been modified or a modified time is not available
+        self._provide_dummy_scale_adapter()
+        storage = self.storage
+        scale = storage.pre_scale(width=50, height=80)
+        uid = scale["uid"]
+        storage.modified = lambda: 100
+        real = storage.get_or_generate(uid)
+        self.assertEqual(real["uid"], uid)
+
     def testScaleForExistingScale(self):
         self._provide_dummy_scale_adapter()
         storage = self.storage