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Refactoring with Codemods to Automate API Adjustments


As a library developer, chances are you’ll create a preferred utility that tons of of
1000’s of builders depend on each day, reminiscent of lodash or React. Over time,
utilization patterns may emerge that transcend your preliminary design. When this
occurs, chances are you’ll want to increase an API by including parameters or modifying
operate signatures to repair edge circumstances. The problem lies in rolling out
these breaking modifications with out disrupting your customers’ workflows.

That is the place codemods are available in—a strong device for automating
large-scale code transformations, permitting builders to introduce breaking
API modifications, refactor legacy codebases, and keep code hygiene with
minimal guide effort.

On this article, we’ll discover what codemods are and the instruments you’ll be able to
use to create them, reminiscent of jscodeshift, hypermod.io, and codemod.com. We’ll stroll by means of real-world examples,
from cleansing up function toggles to refactoring element hierarchies.
You’ll additionally learn to break down advanced transformations into smaller,
testable items—a apply often called codemod composition—to make sure
flexibility and maintainability.

By the top, you’ll see how codemods can grow to be a significant a part of your
toolkit for managing large-scale codebases, serving to you retain your code clear
and maintainable whereas dealing with even probably the most difficult refactoring
duties.

Breaking Adjustments in APIs

Returning to the state of affairs of the library developer, after the preliminary
launch, new utilization patterns emerge, prompting the necessity to lengthen an
API—maybe by including a parameter or modifying a operate signature to
make it simpler to make use of.

For easy modifications, a fundamental find-and-replace within the IDE may work. In
extra advanced circumstances, you may resort to utilizing instruments like sed
or awk. Nonetheless, when your library is extensively adopted, the
scope of such modifications turns into more durable to handle. You’ll be able to’t be certain how
extensively the modification will affect your customers, and the very last thing
you need is to interrupt current performance that doesn’t want
updating.

A standard method is to announce the breaking change, launch a brand new
model, and ask customers emigrate at their very own tempo. However this workflow,
whereas acquainted, typically would not scale properly, particularly for main shifts.
Take into account React’s transition from class elements to operate elements
with hooks—a paradigm shift that took years for big codebases to completely
undertake. By the point groups managed emigrate, extra breaking modifications had been
typically already on the horizon.

For library builders, this case creates a burden. Sustaining
a number of older variations to assist customers who haven’t migrated is each
pricey and time-consuming. For customers, frequent modifications danger eroding belief.
They could hesitate to improve or begin exploring extra secure alternate options,
which perpetuating the cycle.

However what if you happen to might assist customers handle these modifications robotically?
What if you happen to might launch a device alongside your replace that refactors
their code for them—renaming features, updating parameter order, and
eradicating unused code with out requiring guide intervention?

That’s the place codemods are available in. A number of libraries, together with React
and Subsequent.js, have already embraced codemods to easy the trail for model
bumps. For instance, React gives codemods to deal with the migration from
older API patterns, just like the previous Context API, to newer ones.

So, what precisely is the codemod we’re speaking about right here?

What’s a Codemod?

A codemod (code modification) is an automatic script used to rework
code to observe new APIs, syntax, or coding requirements. Codemods use
Summary Syntax Tree (AST) manipulation to use constant, large-scale
modifications throughout codebases. Initially developed at Fb, codemods helped
engineers handle refactoring duties for big tasks like React. As
Fb scaled, sustaining the codebase and updating APIs grew to become
more and more troublesome, prompting the event of codemods.

Manually updating 1000’s of information throughout completely different repositories was
inefficient and error-prone, so the idea of codemods—automated scripts
that rework code—was launched to sort out this drawback.

The method sometimes entails three most important steps:

  1. Parsing the code into an AST, the place every a part of the code is
    represented as a tree construction.
  2. Modifying the tree by making use of a metamorphosis, reminiscent of renaming a
    operate or altering parameters.
  3. Rewriting the modified tree again into the supply code.

By utilizing this method, codemods make sure that modifications are utilized
persistently throughout each file in a codebase, decreasing the prospect of human
error. Codemods may also deal with advanced refactoring eventualities, reminiscent of
modifications to deeply nested constructions or eradicating deprecated API utilization.

If we visualize the method, it could look one thing like this:

Refactoring with Codemods to Automate API Adjustments

Determine 1: The three steps of a typical codemod course of

The thought of a program that may “perceive” your code after which carry out
computerized transformations isn’t new. That’s how your IDE works whenever you
run refactorings like Extract Perform, Rename Variable, or Inline Perform.
Primarily, your IDE parses the supply code into ASTs and applies
predefined transformations to the tree, saving the consequence again into your
information.

For contemporary IDEs, many issues occur beneath the hood to make sure modifications
are utilized appropriately and effectively, reminiscent of figuring out the scope of
the change and resolving conflicts like variable title collisions. Some
refactorings even immediate you to enter parameters, reminiscent of when utilizing
Change Perform Declaration, the place you’ll be able to regulate the
order of parameters or default values earlier than finalizing the change.

Use jscodeshift in JavaScript Codebases

Let’s have a look at a concrete instance to know how we might run a
codemod in a JavaScript challenge. The JavaScript neighborhood has a number of
instruments that make this work possible, together with parsers that convert supply
code into an AST, in addition to transpilers that may rework the tree into
different codecs (that is how TypeScript works). Moreover, there are
instruments that assist apply codemods to total repositories robotically.

Some of the standard instruments for writing codemods is jscodeshift, a toolkit maintained by Fb.
It simplifies the creation of codemods by offering a strong API to
manipulate ASTs. With jscodeshift, builders can seek for particular
patterns within the code and apply transformations at scale.

You should utilize jscodeshift to establish and substitute deprecated API calls
with up to date variations throughout a whole challenge.

Let’s break down a typical workflow for composing a codemod
manually.

Clear a Stale Function Toggle

Let’s begin with a easy but sensible instance to show the
energy of codemods. Think about you’re utilizing a function
toggle
in your
codebase to regulate the discharge of unfinished or experimental options.
As soon as the function is dwell in manufacturing and dealing as anticipated, the subsequent
logical step is to wash up the toggle and any associated logic.

As an illustration, think about the next code:

const knowledge = featureToggle('feature-new-product-list') ? { title: 'Product' } : undefined;

As soon as the function is totally launched and not wants a toggle, this
may be simplified to:

const knowledge = { title: 'Product' };

The duty entails discovering all cases of featureToggle within the
codebase, checking whether or not the toggle refers to
feature-new-product-list, and eradicating the conditional logic surrounding
it. On the similar time, different function toggles (like
feature-search-result-refinement, which can nonetheless be in growth)
ought to stay untouched. The codemod must perceive the construction
of the code to use modifications selectively.

Understanding the AST

Earlier than we dive into writing the codemod, let’s break down how this
particular code snippet seems in an AST. You should utilize instruments like AST
Explorer
to visualise how supply code and AST
are mapped. It’s useful to know the node varieties you are interacting
with earlier than making use of any modifications.

The picture beneath reveals the syntax tree by way of ECMAScript syntax. It
incorporates nodes like Identifier (for variables), StringLiteral (for the
toggle title), and extra summary nodes like CallExpression and
ConditionalExpression.

Determine 2: The Summary Syntax Tree illustration of the function toggle verify

On this AST illustration, the variable knowledge is assigned utilizing a
ConditionalExpression. The take a look at a part of the expression calls
featureToggle('feature-new-product-list'). If the take a look at returns true,
the consequent department assigns { title: 'Product' } to knowledge. If
false, the alternate department assigns undefined.

For a process with clear enter and output, I choose writing exams first,
then implementing the codemod. I begin by defining a damaging case to
guarantee we don’t by chance change issues we need to depart untouched,
adopted by an actual case that performs the precise conversion. I start with
a easy state of affairs, implement it, then add a variation (like checking if
featureToggle is named inside an if assertion), implement that case, and
guarantee all exams move.

This method aligns properly with Check-Pushed Growth (TDD), even
if you happen to don’t apply TDD often. Understanding precisely what the
transformation’s inputs and outputs are earlier than coding improves security and
effectivity, particularly when tweaking codemods.

With jscodeshift, you’ll be able to write exams to confirm how the codemod
behaves:

const rework = require("../remove-feature-new-product-list");

defineInlineTest(
  rework,
  {},
  `
  const knowledge = featureToggle('feature-new-product-list') ? { title: 'Product' } : undefined;
  `,
  `
  const knowledge = { title: 'Product' };
  `,
  "delete the toggle feature-new-product-list in conditional operator"
);

The defineInlineTest operate from jscodeshift lets you outline
the enter, anticipated output, and a string describing the take a look at’s intent.
Now, working the take a look at with a standard jest command will fail as a result of the
codemod isn’t written but.

The corresponding damaging case would make sure the code stays unchanged
for different function toggles:

defineInlineTest(
  rework,
  {},
  `
  const knowledge = featureToggle('feature-search-result-refinement') ? { title: 'Product' } : undefined;
  `,
  `
  const knowledge = featureToggle('feature-search-result-refinement') ? { title: 'Product' } : undefined;
  `,
  "don't change different function toggles"
);

Writing the Codemod

Let’s begin by defining a easy rework operate. Create a file
known as rework.js with the next code construction:

module.exports = operate(fileInfo, api, choices) {
  const j = api.jscodeshift;
  const root = j(fileInfo.supply);

  // manipulate the tree nodes right here

  return root.toSource();
};

This operate reads the file right into a tree and makes use of jscodeshift’s API to
question, modify, and replace the nodes. Lastly, it converts the AST again to
supply code with .toSource().

Now we will begin implementing the rework steps:

  1. Discover all cases of featureToggle.
  2. Confirm that the argument handed is 'feature-new-product-list'.
  3. Change your entire conditional expression with the consequent half,
    successfully eradicating the toggle.

Right here’s how we obtain this utilizing jscodeshift:

module.exports = operate (fileInfo, api, choices) {
  const j = api.jscodeshift;
  const root = j(fileInfo.supply);

  // Discover ConditionalExpression the place the take a look at is featureToggle('feature-new-product-list')
  root
    .discover(j.ConditionalExpression, {
      take a look at: {
        callee: { title: "featureToggle" },
        arguments: [{ value: "feature-new-product-list" }],
      },
    })
    .forEach((path) => {
      // Change the ConditionalExpression with the 'consequent'
      j(path).replaceWith(path.node.consequent);
    });

  return root.toSource();
};

The codemod above:

  • Finds ConditionalExpression nodes the place the take a look at calls
    featureToggle('feature-new-product-list').
  • Replaces your entire conditional expression with the resultant (i.e., {
    title: 'Product' }
    ), eradicating the toggle logic and leaving simplified code
    behind.

This instance demonstrates how straightforward it’s to create a helpful
transformation and apply it to a big codebase, considerably decreasing
guide effort.

You’ll want to jot down extra take a look at circumstances to deal with variations like
if-else statements, logical expressions (e.g.,
!featureToggle('feature-new-product-list')), and so forth to make the
codemod strong in real-world eventualities.

As soon as the codemod is prepared, you’ll be able to check it out on a goal codebase,
such because the one you are engaged on. jscodeshift gives a command-line
device that you need to use to use the codemod and report the outcomes.

$ jscodeshift -t transform-name src/

After validating the outcomes, verify that each one useful exams nonetheless
move and that nothing breaks—even if you happen to’re introducing a breaking change.
As soon as happy, you’ll be able to commit the modifications and lift a pull request as
a part of your regular workflow.

Codemods Enhance Code High quality and Maintainability

Codemods aren’t simply helpful for managing breaking API modifications—they will
considerably enhance code high quality and maintainability. As codebases
evolve, they typically accumulate technical debt, together with outdated function
toggles, deprecated strategies, or tightly coupled elements. Manually
refactoring these areas may be time-consuming and error-prone.

By automating refactoring duties, codemods assist hold your codebase clear
and freed from legacy patterns. Frequently making use of codemods lets you
implement new coding requirements, take away unused code, and modernize your
codebase with out having to manually modify each file.

Refactoring an Avatar Element

Now, let’s have a look at a extra advanced instance. Suppose you’re working with
a design system that features an Avatar element tightly coupled with a
Tooltip. Every time a person passes a title prop into the Avatar, it
robotically wraps the avatar with a tooltip.

Determine 3: A avatar element with a tooltip

Right here’s the present Avatar implementation:

import { Tooltip } from "@design-system/tooltip";

const Avatar = ({ title, picture }: AvatarProps) => {
  if (title) {
    return (
      
        
      
    );
  }

  return ;
};

The purpose is to decouple the Tooltip from the Avatar element,
giving builders extra flexibility. Builders ought to have the ability to determine
whether or not to wrap the Avatar in a Tooltip. Within the refactored model,
Avatar will merely render the picture, and customers can apply a Tooltip
manually if wanted.

Right here’s the refactored model of Avatar:

const Avatar = ({ picture }: AvatarProps) => {
  return ;
};

Now, customers can manually wrap the Avatar with a Tooltip as
wanted:

import { Tooltip } from "@design-system/tooltip";
import { Avatar } from "@design-system/avatar";

const UserProfile = () => {
  return (
    
      
    
  );
};

The problem arises when there are tons of of Avatar usages unfold
throughout the codebase. Manually refactoring every occasion could be extremely
inefficient, so we will use a codemod to automate this course of.

Utilizing instruments like AST Explorer, we will
examine the element and see which nodes characterize the Avatar utilization
we’re concentrating on. An Avatar element with each title and picture props
is parsed into an summary syntax tree as proven beneath:

Determine 4: AST of the Avatar element utilization

Writing the Codemod

Let’s break down the transformation into smaller duties:

  • Discover Avatar utilization within the element tree.
  • Test if the title prop is current.
    • If not, do nothing.
    • If current:
      • Create a Tooltip node.
      • Add the title to the Tooltip.
      • Take away the title from Avatar.
      • Add Avatar as a toddler of the Tooltip.
      • Change the unique Avatar node with the brand new Tooltip.

To start, we’ll discover all cases of Avatar (I’ll omit a few of the
exams, however you must write comparability exams first).

defineInlineTest(
    { default: rework, parser: "tsx" },
    {},
    `
    
    `,
    `
    
      
    
    `,
    "wrap avatar with tooltip when title is supplied"
  );

Much like the featureToggle instance, we will use root.discover with
search standards to find all Avatar nodes:

root
  .discover(j.JSXElement, {
    openingElement: { title: { title: "Avatar" } },
  })
  .forEach((path) => {
    // now we will deal with every Avatar occasion
  });

Subsequent, we verify if the title prop is current:

root
  .discover(j.JSXElement, {
    openingElement: { title: { title: "Avatar" } },
  })
  .forEach((path) => {
    const avatarNode = path.node;

    const nameAttr = avatarNode.openingElement.attributes.discover(
      (attr) => attr.title.title === "title"
    );

    if (nameAttr) {
      const tooltipElement = createTooltipElement(
        nameAttr.worth.worth,
        avatarNode
      );
      j(path).replaceWith(tooltipElement);
    }
  });

For the createTooltipElement operate, we use the
jscodeshift API to create a brand new JSX node, with the title
prop utilized to the Tooltip and the Avatar
element as a toddler. Lastly, we name replaceWith to
substitute the present path.

Right here’s a preview of the way it seems in
Hypermod, the place the codemod is written on
the left. The highest half on the correct is the unique code, and the underside
half is the reworked consequence:

Determine 5: Run checks inside hypermod earlier than apply it to your codebase

This codemod searches for all cases of Avatar. If a
title prop is discovered, it removes the title prop
from Avatar, wraps the Avatar inside a
Tooltip, and passes the title prop to the
Tooltip.

By now, I hope it’s clear that codemods are extremely helpful and
that the workflow is intuitive, particularly for large-scale modifications the place
guide updates could be an enormous burden. Nonetheless, that is not the entire
image. Within the subsequent part, I’ll make clear a few of the challenges
and the way we will deal with these less-than-ideal points.

Fixing Frequent Pitfalls of Codemods

As a seasoned developer, the “joyful path” is barely a small half
of the total image. There are quite a few eventualities to contemplate when writing
a metamorphosis script to deal with code robotically.

Builders write code in quite a lot of kinds. For instance, somebody
may import the Avatar element however give it a special title as a result of
they may have one other Avatar element from a special package deal:

import { Avatar as AKAvatar } from "@design-system/avatar";

const UserInfo = () => (
  <AKAvatar title="Juntao Qiu" picture="/juntao.qiu.avatar.png" />
);

A easy textual content seek for Avatar received’t work on this case. You’ll want
to detect the alias and apply the transformation utilizing the right
title.

One other instance arises when coping with Tooltip imports. If the file
already imports Tooltip however makes use of an alias, the codemod should detect that
alias and apply the modifications accordingly. You’ll be able to’t assume that the
element named Tooltip is all the time the one you’re on the lookout for.

Within the function toggle instance, somebody may use
if(featureToggle('feature-new-product-list')), or assign the results of
the toggle operate to a variable earlier than utilizing it:

const shouldEnableNewFeature = featureToggle('feature-new-product-list');

if (shouldEnableNewFeature) {
  //...
}

They could even use the toggle with different circumstances or apply logical
negation, making the logic extra advanced:

const shouldEnableNewFeature = featureToggle('feature-new-product-list');

if (!shouldEnableNewFeature && someOtherLogic) {
  //...
}

These variations make it troublesome to foresee each edge case,
growing the chance of unintentionally breaking one thing. Relying solely
on the circumstances you’ll be able to anticipate isn’t sufficient. You want thorough testing
to keep away from breaking unintended components of the code.

Leveraging Supply Graphs and Check-Pushed Codemods

To deal with these complexities, codemods needs to be used alongside different
strategies. As an illustration, just a few years in the past, I participated in a design
system elements rewrite challenge at Atlassian. We addressed this situation by
first looking the supply graph, which contained nearly all of inner
element utilization. This allowed us to know how elements had been used,
whether or not they had been imported beneath completely different names, or whether or not sure
public props had been incessantly used. After this search part, we wrote our
take a look at circumstances upfront, making certain we lined nearly all of use circumstances, and
then developed the codemod.

In conditions the place we could not confidently automate the improve, we
inserted feedback or “TODOs” on the name websites. This allowed the
builders working the script to deal with particular circumstances manually. Often,
there have been solely a handful of such cases, so this method nonetheless proved
useful for upgrading variations.

Using Current Code Standardization Instruments

As you’ll be able to see, there are many edge circumstances to deal with, particularly in
codebases past your management—reminiscent of exterior dependencies. This
complexity implies that utilizing codemods requires cautious supervision and a
evaluation of the outcomes.

Nonetheless, in case your codebase has standardization instruments in place, reminiscent of a
linter that enforces a specific coding type, you’ll be able to leverage these
instruments to scale back edge circumstances. By implementing a constant construction, instruments
like linters assist slender down the variations in code, making the
transformation simpler and minimizing surprising points.

As an illustration, you possibly can use linting guidelines to limit sure patterns,
reminiscent of avoiding nested conditional (ternary) operators or implementing named
exports over default exports. These guidelines assist streamline the codebase,
making codemods extra predictable and efficient.

Moreover, breaking down advanced transformations into smaller, extra
manageable ones lets you sort out particular person points extra exactly. As
we’ll quickly see, composing smaller codemods could make dealing with advanced
modifications extra possible.

Codemod Composition

Let’s revisit the function toggle elimination instance mentioned earlier. Within the code snippet
we’ve got a toggle known as feature-convert-new must be eliminated:

import { featureToggle } from "./utils/featureToggle";

const convertOld = (enter: string) => {
  return enter.toLowerCase();
};

const convertNew = (enter: string) => {
  return enter.toUpperCase();
};

const consequence = featureToggle("feature-convert-new")
  ? convertNew("Whats up, world")
  : convertOld("Whats up, world");

console.log(consequence);

The codemod for take away a given toggle works fantastic, and after working the codemod,
we wish the supply to appear to be this:

const convertNew = (enter: string) => {
  return enter.toUpperCase();
};

const consequence = convertNew("Whats up, world");

console.log(consequence);

Nonetheless, past eradicating the function toggle logic, there are further duties to
deal with:

  • Take away the unused convertOld operate.
  • Clear up the unused featureToggle import.

In fact, you possibly can write one huge codemod to deal with every little thing in a
single move and take a look at it collectively. Nonetheless, a extra maintainable method is
to deal with codemod logic like product code: break the duty into smaller,
unbiased items—similar to how you’ll usually refactor manufacturing
code.

Breaking It Down

We are able to break the large transformation down into smaller codemods and
compose them. The benefit of this method is that every transformation
may be examined individually, protecting completely different circumstances with out interference.
Furthermore, it lets you reuse and compose them for various
functions.

As an illustration, you may break it down like this:

  • A metamorphosis to take away a particular function toggle.
  • One other transformation to wash up unused imports.
  • A metamorphosis to take away unused operate declarations.

By composing these, you’ll be able to create a pipeline of transformations:

import { removeFeatureToggle } from "./remove-feature-toggle";
import { removeUnusedImport } from "./remove-unused-import";
import { removeUnusedFunction } from "./remove-unused-function";

import { createTransformer } from "./utils";

const removeFeatureConvertNew = removeFeatureToggle("feature-convert-new");

const rework = createTransformer([
  removeFeatureConvertNew,
  removeUnusedImport,
  removeUnusedFunction,
]);

export default rework;

On this pipeline, the transformations work as follows:

  1. Take away the feature-convert-new toggle.
  2. Clear up the unused import assertion.
  3. Take away the convertOld operate because it’s not used.

Determine 6: Compose transforms into a brand new rework

You may also extract further codemods as wanted, combining them in
varied orders relying on the specified consequence.

Determine 7: Put completely different transforms right into a pipepline to type one other rework

The createTransformer Perform

The implementation of the createTransformer operate is comparatively
simple. It acts as a higher-order operate that takes an inventory of
smaller rework features, iterates by means of the listing to use them to
the foundation AST, and eventually converts the modified AST again into supply
code.

import { API, Assortment, FileInfo, JSCodeshift, Choices } from "jscodeshift";

kind TransformFunction = { (j: JSCodeshift, root: Assortment): void };

const createTransformer =
  (transforms: TransformFunction[]) =>
  (fileInfo: FileInfo, api: API, choices: Choices) => {
    const j = api.jscodeshift;
    const root = j(fileInfo.supply);

    transforms.forEach((rework) => rework(j, root));
    return root.toSource(choices.printOptions || { quote: "single" });
  };

export { createTransformer };

For instance, you possibly can have a rework operate that inlines
expressions assigning the function toggle name to a variable, so in later
transforms you don’t have to fret about these circumstances anymore:

const shouldEnableNewFeature = featureToggle('feature-convert-new');

if (!shouldEnableNewFeature && someOtherLogic) {
  //...
}

Turns into this:

if (!featureToggle('feature-convert-new') && someOtherLogic) {
  //...
}

Over time, you may construct up a group of reusable, smaller
transforms, which might drastically ease the method of dealing with tough edge
circumstances. This method proved extremely efficient in our work refining design
system elements. As soon as we transformed one package deal—such because the button
element—we had just a few reusable transforms outlined, like including feedback
at first of features, eradicating deprecated props, or creating aliases
when a package deal is already imported above.

Every of those smaller transforms may be examined and used independently
or mixed for extra advanced transformations, which hurries up subsequent
conversions considerably. Because of this, our refinement work grew to become extra
environment friendly, and these generic codemods are actually relevant to different inner
and even exterior React codebases.

Since every rework is comparatively standalone, you’ll be able to fine-tune them
with out affecting different transforms or the extra advanced, composed ones. For
occasion, you may re-implement a rework to enhance efficiency—like
decreasing the variety of node-finding rounds—and with complete take a look at
protection, you are able to do this confidently and safely.

Codemods in Different Languages

Whereas the examples we’ve explored up to now give attention to JavaScript and JSX
utilizing jscodeshift, codemods can be utilized to different languages. For
occasion, JavaParser presents the same
mechanism in Java, utilizing AST manipulation to refactor Java code.

Utilizing JavaParser in a Java Codebase

JavaParser may be helpful for making breaking API modifications or refactoring
giant Java codebases in a structured, automated means.

Assume we’ve got the next code in FeatureToggleExample.java, which
checks the toggle feature-convert-new and branches accordingly:

public class FeatureToggleExample {
    public void execute() {
        if (FeatureToggle.isEnabled("feature-convert-new")) {
          newFeature();
        } else {
          oldFeature();
        }
    }

    void newFeature() {
        System.out.println("New Function Enabled");
    }

    void oldFeature() {
        System.out.println("Previous Function");
    }
}

We are able to outline a customer to seek out if statements checking for
FeatureToggle.isEnabled, after which substitute them with the corresponding
true department—much like how we dealt with the function toggle codemod in
JavaScript.

// Customer to take away function toggles
class FeatureToggleVisitor extends VoidVisitorAdapter {
    @Override
    public void go to(IfStmt ifStmt, Void arg) {
        tremendous.go to(ifStmt, arg);
        if (ifStmt.getCondition().isMethodCallExpr()) {
            MethodCallExpr methodCall = ifStmt.getCondition().asMethodCallExpr();
            if (methodCall.getNameAsString().equals("isEnabled") &&
                methodCall.getScope().isPresent() &&
                methodCall.getScope().get().toString().equals("FeatureToggle")) {

                BlockStmt thenBlock = ifStmt.getThenStmt().asBlockStmt();
                ifStmt.substitute(thenBlock);
            }
        }
    }
}

This code defines a customer sample utilizing
JavaParser to traverse and manipulate the AST. The
FeatureToggleVisitor seems for if statements
that decision FeatureToggle.isEnabled() and replaces your entire
if assertion with the true department.

You may also outline guests to seek out unused strategies and take away
them:

class UnusedMethodRemover extends VoidVisitorAdapter {
    personal Set calledMethods = new HashSet<>();
    personal Record methodsToRemove = new ArrayList<>();

    // Accumulate all known as strategies
    @Override
    public void go to(MethodCallExpr n, Void arg) {
        tremendous.go to(n, arg);
        calledMethods.add(n.getNameAsString());
    }

    // Accumulate strategies to take away if not known as
    @Override
    public void go to(MethodDeclaration n, Void arg) {
        tremendous.go to(n, arg);
        String methodName = n.getNameAsString();
        if (!calledMethods.incorporates(methodName) && !methodName.equals("most important")) {
            methodsToRemove.add(n);
        }
    }

    // After visiting, take away the unused strategies
    public void removeUnusedMethods() {
        for (MethodDeclaration technique : methodsToRemove) {
            technique.take away();
        }
    }
}

This code defines a customer, UnusedMethodRemover, to detect and
take away unused strategies. It tracks all known as strategies within the calledMethods
set and checks every technique declaration. If a way isn’t known as and isn’t
most important, it provides it to the listing of strategies to take away. As soon as all strategies are
processed, it removes any unused strategies from the AST.

Composing Java Guests

You’ll be able to chain these guests collectively and apply them to your codebase
like so:

public class FeatureToggleRemoverWithCleanup {
    public static void most important(String[] args) {
        strive {
            String filePath = "src/take a look at/java/com/instance/Instance.java";
            CompilationUnit cu = StaticJavaParser.parse(new FileInputStream(filePath));

            // Apply transformations
            FeatureToggleVisitor toggleVisitor = new FeatureToggleVisitor();
            cu.settle for(toggleVisitor, null);

            UnusedMethodRemover remover = new UnusedMethodRemover();
            cu.settle for(remover, null);
            remover.removeUnusedMethods();

            // Write the modified code again to the file
            strive (FileOutputStream fos = new FileOutputStream(filePath)) {
                fos.write(cu.toString().getBytes());
            }

            System.out.println("Code transformation accomplished efficiently.");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Every customer is a unit of transformation, and the customer sample in
JavaParser makes it straightforward to compose them.

OpenRewrite

One other standard choice for Java tasks is OpenRewrite. It makes use of a special format of the
supply code tree known as Lossless Semantic Bushes (LSTs), which
present extra detailed data in comparison with conventional AST (Summary
Syntax Tree) approaches utilized by instruments like JavaParser or jscodeshift.
Whereas AST focuses on the syntactic construction, LSTs seize each syntax and
semantic which means, enabling extra correct and complex
transformations.

OpenRewrite additionally has a strong ecosystem of open-source refactoring
recipes for duties reminiscent of framework migrations, safety fixes, and
sustaining stylistic consistency. This built-in library of recipes can
save builders vital time by permitting them to use standardized
transformations throughout giant codebases without having to jot down customized
scripts.

For builders who want custom-made transformations, OpenRewrite permits
you to create and distribute your personal recipes, making it a extremely versatile
and extensible device. It’s extensively used within the Java neighborhood and is
steadily increasing into different languages, because of its superior
capabilities and community-driven method.

Variations Between OpenRewrite and JavaParser or jscodeshift

The important thing distinction between OpenRewrite and instruments like JavaParser or
jscodeshift lies of their method to code transformation:

  • OpenRewrite’s Lossless Semantic Bushes (LSTs) seize each the
    syntactic and semantic which means of the code, enabling extra correct
    transformations.
  • JavaParser and jscodeshift depend on conventional ASTs, which focus
    totally on the syntactic construction. Whereas highly effective, they might not all the time
    seize the nuances of how the code behaves semantically.

Moreover, OpenRewrite presents a big library of community-driven
refactoring recipes, making it simpler to use frequent transformations with out
needing to jot down customized codemods from scratch.

Different Instruments for Codemods

Whereas jscodeshift and OpenRewrite are highly effective instruments, there are
different choices value contemplating, relying in your wants and the ecosystem
you are working in.

Hypermod

Hypermod introduces AI help to the codemod writing course of.
As a substitute of manually crafting the codemod logic, builders can describe
the specified transformation in plain English, and Hypermod will generate
the codemod utilizing jscodeshift. This makes codemod creation extra
accessible, even for builders who will not be acquainted with AST
manipulation.

You’ll be able to compose, take a look at, and deploy a codemod to any repository
related to Hypermod. It could possibly run the codemod and generate a pull
request with the proposed modifications, permitting you to evaluation and approve
them. This integration makes your entire course of from codemod growth
to deployment far more streamlined.

Codemod.com

Codemod.com is a community-driven platform the place builders
can share and uncover codemods. In case you want a particular codemod for a
frequent refactoring process or migration, you’ll be able to seek for current
codemods. Alternatively, you’ll be able to publish codemods you’ve created to assist
others within the developer neighborhood.

In case you’re migrating an API and wish a codemod to deal with it,
Codemod.com can prevent time by providing pre-built codemods for
many frequent transformations, decreasing the necessity to write one from
scratch.

Conclusion

Codemods are highly effective instruments that enable builders to automate code
transformations, making it simpler to handle API modifications, refactor legacy
code, and keep consistency throughout giant codebases with minimal guide
intervention. By utilizing instruments like jscodeshift, Hypermod, or
OpenRewrite, builders can streamline every little thing from minor syntax
modifications to main element rewrites, bettering total code high quality and
maintainability.

Nonetheless, whereas codemods provide vital advantages, they don’t seem to be
with out challenges. One of many key issues is dealing with edge circumstances,
notably when the codebase is various or publicly shared. Variations
in coding kinds, import aliases, or surprising patterns can result in
points that codemods could not deal with robotically. These edge circumstances
require cautious planning, thorough testing, and, in some cases, guide
intervention to make sure accuracy.

To maximise the effectiveness of codemods, it’s essential to interrupt
advanced transformations into smaller, testable steps and to make use of code
standardization instruments the place potential. Codemods may be extremely efficient,
however their success will depend on considerate design and understanding the
limitations they might face in additional diversified or advanced codebases.


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