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Presets

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Read https://intentius.io/chant/guide/presets/.
Find property values that several resources of one type repeat, and move them into an exported `const` preset that each resource spreads, as the page shows.
Spread only `const` bindings (EVL004), and remember that a nested object in the preset is replaced, not merged.
Run `npx chant build` and `npx chant lint`, check that the built output is unchanged, and open a pull request.
Never deploy to a real cloud account or shared environment (with `chant run`, `chant components` or a platform's own CLI), approve (a pull request review, `chant approve` or `chant run approve`), override a policy denial (`chant approve policy-override`), or merge; never cut or publish a release (`chant release cut --yes` or `chant release publish`), push or delete a `ci/*` tag (`chant ci tick` pushes them), or change the value of an existing flag; never touch `.chant/allowed_signers` or `chant/lifecycle`.

Presets are shared default values that resource definitions reference. Use one when several resources of the same type share settings.

Defining a Preset

Section titled “Defining a Preset”

Extract shared properties into exported const declarations:

src/preset-defaults.ts
import { ServerSideEncryptionByDefault, PublicAccessBlockConfiguration } from "@intentius/chant-lexicon-aws";


export const encryptionDefault = new ServerSideEncryptionByDefault({
  SSEAlgorithm: "AES256",
});


export const publicAccessBlock = new PublicAccessBlockConfiguration({
  BlockPublicAcls: true,
  BlockPublicPolicy: true,
  IgnorePublicAcls: true,
  RestrictPublicBuckets: true,
});

Using a Preset

Section titled “Using a Preset”

Import the preset and use it in resource properties:

src/preset-usage.ts
import { Bucket, BucketEncryption, ServerSideEncryptionRule, Sub, AWS, Ref } from "@intentius/chant-lexicon-aws";
import { publicAccessBlock, encryptionDefault } from "./preset-defaults";
import { environment } from "./parameters";


export const secureBucket = new Bucket({
  BucketName: Sub`${AWS.StackName}-${Ref(environment)}-secure-data`,
  PublicAccessBlockConfiguration: publicAccessBlock,
  BucketEncryption: new BucketEncryption({
    ServerSideEncryptionConfiguration: [
      new ServerSideEncryptionRule({
        ServerSideEncryptionByDefault: encryptionDefault,
      }),
    ],
  }),
});

Properties listed after the preset reference override the preset values.

Rules

Section titled “Rules”
  • The spread source must be a const binding, declared in the file or imported from another module. Spreading from let, var, or function calls triggers lint rule EVL004.
  • Preset objects are plain data, not resource instances.
  • Properties in the spread are merged shallowly. Nested objects are replaced entirely, not deep-merged.

See your lexicon’s documentation for working preset examples with concrete resource types.

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