Fix TypeError in _nonNegativeDelta when val is None and maxValue is set

[npazosmendez]

_nonNegativeDelta compared val against maxValue/minValue before checking whether val is None, causing a TypeError when a series contains None values and maxValue (or minValue) is provided.

Fix: move the None in (prev, val) early-return before the comparisons. This also makes semantic sense — on the first reading or a None value there is no delta to compute, regardless of bounds.

The added test case reproduces the issue, and fails without the fix:

  ======================================================================
     ERROR: test_perSecond_nones (tests.test_functions.FunctionsTest.test_perSecond_nones)
     ----------------------------------------------------------------------
     Traceback (most recent call last):
       File "/home/nicolas/code/graphite-web/webapp/tests/test_functions.py", line 1802, in test_perSecond_nones
         result = functions.perSecond({}, seriesList, maxValue=1000)
       File "/home/nicolas/code/graphite-web/webapp/graphite/render/functions.py", line 2230, in perSecond
         delta, prev = _nonNegativeDelta(val, prev, maxValue, minValue)
                       ~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
       File "/home/nicolas/code/graphite-web/webapp/graphite/render/functions.py", line 2431, in _nonNegativeDelta
         if maxValue is not None and val > maxValue:
                                     ^^^^^^^^^^^^^^
     TypeError: '>' not supported between instances of 'NoneType' and 'int'

     ----------------------------------------------------------------------
     Ran 1 test in 0.003s

[deniszh]

Not sure about this... it's definitely changing function behaviour - see broken tests.

[npazosmendez]

@deniszh sorry I had missed those failures locally. I did spot the behavior change but it seemed harmless to me. I guess it's not. Reworked, behavior should be preserved now. All tests pass locally

[Copilot]

Pull request overview

Fixes a runtime TypeError in Graphite’s rate/delta helpers when processing series containing None values while maxValue/minValue bounds are provided, ensuring perSecond() (and callers of _nonNegativeDelta) safely handle sparse data.

Changes:

• Add an early return in _nonNegativeDelta for val is None to avoid invalid comparisons against maxValue/minValue.
• Simplify the “first reading” check to prev is None (since val is None is now handled upfront).
• Add a regression assertion in test_perSecond_nones to cover perSecond(..., maxValue=...) with None values.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
webapp/graphite/render/functions.py	Prevents TypeError by guarding None values before bound comparisons in _nonNegativeDelta.
webapp/tests/test_functions.py	Adds a regression check ensuring perSecond with maxValue handles None datapoints without crashing.

---

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[Copilot]

The new maxValue regression assertion only compares the values via list(...), but doesn’t assert the full TimeSeries equality (name/start/end/step/tags). For consistency with nearby perSecond tests (e.g., test_perSecond_float / test_perSecond_max) and to ensure metadata doesn’t regress, add self.assertEqual(expected, result) (or an equivalent full-object assertion) for this new call as well.

Suggested change

	self.assertEqual(list(expected[0]), list(result[0]))
	self.assertEqual(list(expected[0]), list(result[0]))
	self.assertEqual(expected, result)

[codecov-commenter]

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.90%. Comparing base (5df4cd4) to head (f86f943).
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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2912      +/-   ##
==========================================
+ Coverage   76.80%   76.90%   +0.09%     
==========================================
  Files          88       88              
  Lines        9700     9703       +3     
  Branches     1805     1806       +1     
==========================================
+ Hits         7450     7462      +12     
+ Misses       1983     1971      -12     
- Partials      267      270       +3     

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