3.6. Checking for a Compatible Semver Version

To check if a change from a semver version a to a semver version b is compatible according to semver rule, use the method is_compatible().

The expression a.is_compatible(b) is True if one of the following statements is true:

• both versions are equal, or

• both majors are equal and higher than 0. The same applies for both minor parts. Both pre-releases are equal, or

• both majors are equal and higher than 0. The minor of b’s minor version is higher then a’s. Both pre-releases are equal.

In all other cases, the result is false.

Keep in mind, the method does not check patches!

• Two different majors:

  >>> a = Version(1, 1, 1)
  >>> b = Version(2, 0, 0)
  >>> a.is_compatible(b)
  False
  >>> b.is_compatible(a)
  False
  

• Two different minors:

  >>> a = Version(1, 1, 0)
  >>> b = Version(1, 0, 0)
  >>> a.is_compatible(b)
  False
  >>> b.is_compatible(a)
  True
  

• The same two majors and minors:

  >>> a = Version(1, 1, 1)
  >>> b = Version(1, 1, 0)
  >>> a.is_compatible(b)
  True
  >>> b.is_compatible(a)
  True
  

• Release and pre-release:

  >>> a = Version(1, 1, 1)
  >>> b = Version(1, 0, 0,'rc1')
  >>> a.is_compatible(b)
  False
  >>> b.is_compatible(a)
  False
  

• Different pre-releases:

  >>> a = Version(1, 0, 0, 'rc1')
  >>> b = Version(1, 0, 0, 'rc2')
  >>> a.is_compatible(b)
  False
  >>> b.is_compatible(a)
  False
  

• Identical pre-releases:

  >>> a = Version(1, 0, 0,'rc1')
  >>> b = Version(1, 0, 0,'rc1')
  >>> a.is_compatible(b)
  True
  

• All major zero versions are incompatible with anything but itself:

  >>> Version(0, 1, 0).is_compatible(Version(0, 1, 1))
  False
  
  # Only identical versions are compatible for major zero versions:
  >>> Version(0, 1, 0).is_compatible(Version(0, 1, 0))
  True