Full project refactoring, extract method refactoring

Nov 11, 2020

Extract Method Refactoring

Sourcery can now propose refactorings to extract blocks of code into new functions. This currently proposes in two circumstances:

• When finding duplicate and near duplicate blocks of code within a single function
• When finding a large block of code in the function that would be better off in it’s own function

This feature will be available in the upcoming Pro subscription.

Full project scan for refactorings

Select the project or a folder within a project in the IDE plugins, and then have Sourcery scan every file within it. All refactoring suggestions will be displayed as they are found in the Problems window.

This makes it easy to refactor a large portion of the codebase quickly without manually having to visit every file to see the Sourcery suggestions.

This feature will be available in the upcoming Pro subscription.

Improve project and module code metrics in Quality Report

Previously when aggregating metrics we simply calculated metrics for each function and then averaged them. This did not account for the differing size of functions - a 100 line function has more impact on quality than a 10 line one.

We now weight each metric (apart from method length) by the number of lines in each method when averaging them. This gives a better view of the actual file and project-level quality.

New Refactorings

Hoist code from else after guard clause: remove-else-after-guard

Hoist code from an else after a guard clause. This will happen where the main body of an if contains only a raise or return statement, and there are multiple statements in the else.

def f(a=None):
    if a is None:
        return 42
    else:
        # some long statement
        var = (i**2 for i in range(a))
        return sum(var)

is converted into:

def f(a=None):
    if a is None:
        return 42

    # some long statement
    var = (i**2 for i in range(a))
    return sum(var)

Inline variable that is immediately returned after if

Where a value is set on each branch of an if and then immediately returned, instead return it directly from each branch.

def f():
    if condition:
        val = 42
    else:
        val = 0
    return val

is converted into:

def f():
    if condition:
        return 42
    else:
        return 0

Add Command Line Interface —backup option

Use with sourcery refactor --in-place to backup changed files with given suffix:

sourcery refactor --in-place --backup .bak main.py

If any refactorings are found in main.py a copy will be made at main.py.bak before it is updated in place.

Bug Fixes and other adjustments

• Only propose for-index-replacement for lists, as it’s possible __len__ and __getitem__ are implemented but __iter__ is not.
• Minor changes to the swap-if-else refactoring. This will now also be triggered where it can enable the above remove-else-after-guard refactoring. The description has also changed to reflect this.
• Fix issue where block comments above a changed line stopped refactorings being suggested
• We now don’t convert an if/else to an if expression where the test contains a boolean operation. This prevents creation of hard-to-read if expression lines.
• Quality warnings in PyCharm Problems pane no longer show as raw HTML
• IDE Code metrics now have link to our documentation. We have added a title to the code metrics in the IDE with a link to our documentation. This will let you easily see how the metrics are calculated and how to improve your code.
• Fix formatting issue in Vim where a blank line was deleted after the refactored function