When comparing to booleans, we perform magic castings and get unexpected results.
TL;DR: Don't compare against true. Either you are true, or false or you shouldn't compare
Problems
Hidden castings
The least surprise principle violation.
Fail Fast principle violation
Solutions
Use booleans
Don't mix booleans with boolean castable objects
Context
Many languages cast values to boolean crossing domains.
Sample Code
Wrong
#!/bin/bash
if [ false ]; then
echo "True"
else
echo "False"
fi
# this evaluates to true since
# "false" is a non-empty string
if [ false ] = true; then
echo "True"
else
echo "False"
fi
# this also evaluates to true
Right
#!/bin/bash
if false ; then
echo "True"
else
echo "False"
fi
# this evaluates to false
Detection
[X] Automatic
Linters can check for explicit comparisons and warnings.
Tags
- Castings
Conclusion
It is a common industry practice to use many non booleans as booleans.
We should be very strict when using booleans.
Relations
Code Smell 69 - Big Bang (JavaScript Ridiculous Castings)
Maxi Contieri ・ May 4 '21
More Info
Credits
Photo by Michael Held on Unsplash
If it doesn’t work, it doesn’t matter how fast it doesn’t work.
Mich Ravera
Software Engineering Great Quotes
Maxi Contieri ・ Dec 28 '20
This article is part of the CodeSmell Series.
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