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A jscodeshift Codemod to convert curly braces syntax to angle brackets syntax for templates in an Ember.js app

Refer to this RFC for more details on Angle brackets invocation syntax.


This codemod currently only supports Ember's classic filesystem layout, meaning it won't work if your app uses pods. For more info, see this issue.


WARNING: jscodeshift, and thus this codemod, edits your files in place. It does not make a copy. Make sure your code is checked into a source control repository like Git and that you have no outstanding changes to commit before running this tool.

  1. Start your ember development server
  2. Run Codemod, pointing it at the address of the development server
$ cd my-ember-app-or-addon
$ npx ember-angle-brackets-codemod --telemetry=http://localhost:4200 ./path/of/files/ or ./some**/*glob.hbs

Telemetry helpers runs the app, grabs basic info about all of the modules at runtime. This allows the codemod to know the names of every helper, component, route, controller, etc. in the app without guessing / relying on static analysis. They basically help you to create "runtime assisted codemods".

See "Gathering runtime data" section of ember-native-class-codemod for some additonal information.

Running the codemod without Telemetry

$ cd my-ember-app-or-addon
$ npx ember-angle-brackets-codemod ./path/of/files/ or ./some**/*glob.hbs

NOTE If you are not using telemetry, you will probably need to manually configure the codemod to at least skip any helpers that are invoked in the template files you are running it on.


{{site-header user=this.user class=(if this.user.isAdmin "admin")}}

{{#super-select selected=this.user.country as |s|}}
  {{#each this.availableCountries as |country|}}
    {{#s.option value=country}}{{country.name}}{{/s.option}}

{{ui/button text="Click me"}}


<SiteHeader @user={{this.user}} class={{if this.user.isAdmin "admin"}} />
<SuperSelect @selected={{this.user.country}} as |s|>
  {{#each this.availableCountries as |country|}}
    <s.option @value={{country}}>

<Ui::Button @text="Click me" />

Advanced Usage

Skipping helpers

To help the codemod disambiguate components and helpers, you can define a list of helpers from your application in a configuration file as follows:


  "helpers": [

The codemod will then ignore the above list of helpers and prevent them from being transformed into the new angle-brackets syntax.

You can also disable the conversion of the built-in components {{link-to}}, {{input}} and {{textarea}} as follows:


  "helpers": [],
  "skipBuiltInComponents": true

You can execute the codemod with custom configuration by specifying a --config command line option as follows:

$ cd my-ember-app-or-addon
$ npx ember-angle-brackets-codemod angle-brackets app/templates --config ./config/anglebrackets-codemod-config.json

To get a list of helpers in your app you can do this in the Developer Console in your browser inside of your app:

var componentLikeHelpers = Object.keys(require.entries)
  .filter(name => name.includes('/helpers/') || name.includes('/helper'))
  .filter(name => !name.includes('/-'))
  .map(name => {
    let path = name.split('/helpers/');
    return path.pop();
  .filter(name => !name.includes('/'))


Skipping some files

If there are files that don't convert well, you can skip them by specifying an optional skipFilesThatMatchRegex configuration setting. For example, with the configuration below, all files that contain "foo" or "bar" will be skipped:


  "helpers": [],
  "skipBuiltInComponents": true,
  "skipFilesThatMatchRegex": "foo|bar"

Skipping some attributes

If there are cases where some attributes should not be prefixed with @, you can skip them by specifying an optional skipAttributesThatMatchRegex configuration setting. For example, with the configuration below, all attributes that matches either /data-/gim or /aria-/gim will not be prefixed with @:

Processing valueless data test attributes

Curly invocations that have data-test- attributes with no value are not processed by default. The configuration below will cause them to be processed:


  "includeValuelessDataTestAttributes": true


  "helpers": [],
  "skipBuiltInComponents": true,
  "skipAttributesThatMatchRegex": ["/data-/gim", "/aria-/gim"]


  {{some-component data-test-foo=true aria-label="bar" foo=true}}


  <SomeComponent data-test-foo={{true}} aria-label="bar" @foo={{true}} />

Converting specific components only

If you would like to only convert certain component invocations to use the angle brackets syntax, use the components configuration setting and specify component names. For example, with the configuration below, only the {{baz}} and {{bat}} components will be converted, leaving everything else intact.


  "components": ["baz", "bat"]

Making helper invocations unambiguous

You may want to convert invocations like {{concat "foo" "bar"}} into {{(concat "foo" "bar")}}, which may be useful as a temporary step when upgrading to strict-mode Embroider.

In your config/anglebrackets-codemod-config.json, add this:

  "unambiguousHelpers": true

Note that unambiguous helpers do not work in non-Embroider Ember, as of January 2024.

Note that ambiguous invocations that cannot be statically distinguished between a helper, a property and a component — will not be modified.

Debugging Workflow

Oftentimes, you want to debug the codemod or the transform to identify issues with the code or to understand how the transforms are working, or to troubleshoot why some tests are failing.

Hence we recommend a debugging work-flow like below to quickly find out what is causing the issue.

1. Place debugger statements

Add debugger statements, in appropriate places in the code. For example:

const params = a.value.params.map(p => {
  if(p.type === "SubExpression") {
    return transformNestedSubExpression(p)

2. Inspect the process with node debug

Here we are going to start the tests selectively in node debug mode. Since the codemod is using jest in turn to run the tests, jest is having an option -t <name-of-spec> to run a particular set of tests instead of running the whole test suite.

We are making use of both these features to start our tests in this particular fashion. For more details on node debug, visit the official Node.js debugging guide, and for jest documentation on tests, please refer here.

node --inspect-brk ./node_modules/.bin/jest --runInBand --testNamePattern <test-name> 

For example, if you want to debug the null-subexp test or only that particular test case is failing because of an issue.

node --inspect-brk ./node_modules/.bin/jest --runInBand --testNamePattern 'null-subexp' 

Or you can make use of the npm scripts defined in package.json. All you need to pass the test name as the extra parameter with the script.

npm run debug:test 'null-subexp'

Using yarn

yarn debug:test 'null-subexp'

Once you run the above command, your tests will start running in debug mode and your breakpoints will be triggered appropriately when that particular block of code gets executed. You can run the debugger inside Chrome browser dev-tools. More details on here

AST Explorer playground

  1. Go to the AST Explorer
  2. Paste your curly brace syntax code in the top left corner window (Source)
  3. You will get the converted angle bracket syntax in the bottom right corner window (Transform Output)


Known issues

  • No formatting preserved


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