tsconfig-base.json

// TypeScript configuration defaults for each sub-project (src, tools, etc).
{
  "$schema": "https://json.schemastore.org/tsconfig.json",

  "compilerOptions": {
    // enable incremental builds.
    "composite": true,

    // enable type-stripping.
    // "allowImportingTsExtensions": true,
    // "rewriteRelativeImportExtensions": true,

    // maximize type checking.
    "allowUnreachableCode": false,
    "allowUnusedLabels": false,
    "exactOptionalPropertyTypes": true,
    "forceConsistentCasingInFileNames": true,
    "noImplicitOverride": true,
    "noUncheckedIndexedAccess": true,
    "noUncheckedSideEffectImports": true,
    "noUnusedLocals": true,
    "noUnusedParameters": true,
    "resolveJsonModule": true,
    "strict": true,

    // Blocks
    "jsx": "react",
    "jsxFactory": "Devvit.createElement",
    "jsxFragmentFactory": "Devvit.Fragment",

    "types": [], // projects add types needed.

    "isolatedDeclarations": true, // require explicit types.

    // improve compatibility with compilers that aren't type system aware.
    "isolatedModules": true,

    // allow JSON type-checking and imports.
    "module": "ESNext",
    "moduleResolution": "Bundler",

    // assume library types are checked and compatible.
    "skipLibCheck": true,
    "skipDefaultLibCheck": true,

    "sourceMap": true,

    "target": "ES2020",

    // don't transform type-only imports.
    "verbatimModuleSyntax": true
  },
  // https://github.com/microsoft/TypeScript/wiki/Performance#misconfigured-include-and-exclude
  "exclude": ["dist", "node_modules", ".*/"]
}