yoda_condition

NoteAdded in 0.7.0

What it does

Checks for literals on the left of ==, !=, <, <=, >, and >=, or supplied as object in expect_equal(), expect_identical(), and expect_setequal().

Why is this bad?

Putting the expected value before the actual result, as in 1 == x, is called a “Yoda condition”. Writing the actual result first makes comparisons easier to read.

This rule has an unsafe automatic fix because swapping values can change results, for instance due to S3 method dispatch.

Example

1 == x
10 < length(x)
expect_equal(2, x + y)

Use instead:

x == 1
length(x) > 10
expect_equal(x + y, 2)

References

• https://en.wikipedia.org/wiki/Yoda_conditions