Fix precision is not calculated from the rounded uncertainty (#2427)

* Calculate the precision from the rounded uncertainty

* Added doctest

* Make the doc-test more real-life

* Changelog

CHANGES.rst

@@ -4,6 +4,7 @@ Changelog
 2.5.0 (unreleased)
 ------------------
 
+- #2427 Fix precision is not calculated from the rounded uncertainty
 - #2426 Fix ±0 is displayed for results within a range without uncertainty set
 - #2424 Fix sample in "registered" after creation when user cannot receive
 - #2422 Fix Maximum number of Iterations Exceeded when no catalogs set for AT type

src/bika/lims/content/abstractanalysis.py

@@ -953,7 +953,7 @@ def getPrecision(self, result=None):
           in accordance with the manual uncertainty set.
 
         - If Calculate Precision from Uncertainty is set in Analysis Service,
-          calculates the precision in accordance with the uncertainty infered
+          calculates the precision in accordance with the uncertainty inferred
           from uncertainties ranges.
 
         - If neither Manual Uncertainty nor Calculate Precision from
@@ -980,7 +980,23 @@ def getPrecision(self, result=None):
                 strres = str(result)
                 numdecimals = strres[::-1].find('.')
                 return numdecimals
+
+            uncertainty = api.to_float(uncertainty)
+            # Get the 'raw' significant digits from uncertainty
+            sig_digits = get_significant_digits(uncertainty)
+            # Round the uncertainty to its significant digit.
+            # Needed because the precision for the result has to be based on
+            # the *rounded* uncertainty. Note the following for a given
+            # uncertainty value:
+            #   >>> round(0.09404, 2)
+            #   0.09
+            #   >>> round(0.09504, 2)
+            #   0.1
+            # The precision when the uncertainty is 0.09504 is not 2, but 1
+            uncertainty = abs(round(uncertainty, sig_digits))
+            # Return the significant digit to apply
             return get_significant_digits(uncertainty)
+
         return self.getField('Precision').get(self)
 
     @security.public

src/senaite/core/tests/doctests/Uncertainties.rst

@@ -246,6 +246,25 @@ Check the precision of the range 10-20 (0.4):
     >>> fe.getFormattedResult()
     '10.3'
 
+Check the precision is calculated based on the rounded uncertainty:
+
+    >>> uncertainties_2 = [
+    ...    {'intercept_min': '1.0', 'intercept_max': '100000', 'errorvalue': '9.9%'},
+    ...    {'intercept_min': '0.5', 'intercept_max': '0.9', 'errorvalue': '0'}
+    ... ]
+    >>> fe.setUncertainties(uncertainties_2)
+    >>> fe.setResult("9.6")
+    >>> fe.getResult()
+    '9.6'
+
+    >>> fe.getUncertainty()
+    '0.9504'
+
+    >>> fe.getPrecision()
+    0
+
+    >>> fe.getFormattedResult()
+    '10'
 
 Test uncertainty for results above/below detection limits
 .........................................................