chore(internal): revisit tsconfig files

[dreamorosi]

Description of your changes

This PR introduces changes to the TypeScript configuration of the project by revisiting and standardizing the configurations across packages. Before this PR each workspace was defining and maintaining its own TypeScript configuration, this defeated the purpose of using a monorepo structure and made maintenance time consuming.

In this PR we define the main tsconfig.json file at the root of the project and then use the extends option to define a more specific one in each workspace package.

This way the main settings for the project are defined centrally simplifying maintenance and enforcing increased consistency. At the same time, workspace packages can still override any of the settings locally ensuring customizability.

For example, given a tsconfig.json file at the project's root:

{
  "compilerOptions": {
    "incremental": true,
    "composite": true,
    "target": "ES2020", // Node.js 14
    "experimentalDecorators": true, // TODO: remove this once we move to TypeScript 5.x
    "module": "commonjs",
  }
}

we can define a more specific one in packages/logger/tsconfig.json by extending the main one:

{
    "extends": "../../tsconfig.json",
    "compilerOptions": {
        "outDir": "./lib",
        "rootDir": "./src",
    },
    "include": [
        "./src/**/*"
    ],
}

Starting from this PR we also introduce a dedicated tsconfig.json file in the tests directory of each workspace, i.e. packages/logger/tests/tsconfig.json:

{
    "extends": "../tsconfig.json",
    "compilerOptions": {
        "rootDir": "../",
        "noEmit": true
    },
    "include": [
        "../src/**/*",
        "./**/*",
    ]
}

This allows us to finally include the tests as part of the TS configuration but still keep them excluded from the compilation.

In addition to the changes above, we have also reviewed every option available and considered its impact on the project. As a result of this work we have introduced a couple new options that should bring performance improvements at build time:

• Start using references and composite to the project: "Project references are a way to structure your TypeScript programs into smaller pieces. Using Project References can greatly improve build and editor interaction times, enforce logical separation between components, and organize your code in new and improved ways."
• Start using the incremental setting to tell "TypeScript to save information about the project graph from the last compilation to files stored on disk. This creates a series of .tsbuildinfo files in the same folder as your compilation output."

The two changes above open the door to potential additional build performance improvements in the future by caching incremental build artifacts or parallelizing commands but still having TS figure out dependencies between modules.

In addition to the above, we have identified a few other areas that we'd like to experiment in the near future but that we have intentionally left out due to potential breaking changes, like:

• importHelpers, noEmitHelpers, and downlevelIteration which would allow to move helpers to an external tslib module shared across files rather than emitting the same helpers multiple times
• isolatedModules which would allow to ensure that each file can be safely transpiled without relying on other imports, thus further improving build perf

Related issues, RFCs

Issue number: #617

Checklist

• My changes meet the tenets criteria
• I have performed a self-review of my own code
• I have commented my code where necessary, particularly in areas that should be flagged with a TODO, or hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my change is effective and works
• The PR title follows the conventional commit semantics

Breaking change checklist

Is it a breaking change?: NO

• I have documented the migration process
• I have added, implemented necessary warnings (if it can live side by side)

---

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[dreamorosi]

Successful integration test runs:
https://github.com/aws-powertools/powertools-lambda-typescript/actions/runs/6071177219
https://github.com/aws-powertools/powertools-lambda-typescript/actions/runs/6071292281

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