feat(types): Improve type safety in leaf-node modules

Removes `@ts-expect-error` suppressions in `src/utils/shell.ts` and `src/utils/dot-env.ts` by introducing proper type guards and explicit types.

- In `shell.ts`, adds a type assertion to correctly handle the `execa` result when `reject: false` is used.
- In `dot-env.ts`, adds explicit types to function parameters and uses a type predicate with `.filter()` to correctly narrow array types. This also resolves downstream type errors in `dev.ts`.

Author: google-labs-jules[bot]

src/utils/dev.ts

@@ -195,7 +195,6 @@ const getEnvSourceName = (source) => {
 // @ts-expect-error TS(7031) FIXME: Binding element 'devConfig' implicitly has an 'any... Remove this comment to see the full error message
 export const getDotEnvVariables = async ({ devConfig, env, site }): Promise<EnvironmentVariables> => {
   const dotEnvFiles = await loadDotEnvFiles({ envFiles: devConfig.envFiles, projectDir: site.root })
-  // @ts-expect-error TS(2339) FIXME: Property 'env' does not exist on type '{ warning: ... Remove this comment to see the full error message
   dotEnvFiles.forEach(({ env: fileEnv, file }) => {
     const newSourceName = `${file} file`
 

src/utils/dot-env.ts

@@ -7,26 +7,29 @@ import { isFileAsync } from '../lib/fs.js'
 
 import { warn } from './command-helpers.js'
 
-// @ts-expect-error TS(7031) FIXME: Binding element 'envFiles' implicitly has an 'any'... Remove this comment to see the full error message
-export const loadDotEnvFiles = async function ({ envFiles, projectDir }) {
+export const loadDotEnvFiles = async function ({ envFiles, projectDir }: { envFiles?: string[]; projectDir: string }) {
   const response = await tryLoadDotEnvFiles({ projectDir, dotenvFiles: envFiles })
 
-  // @ts-expect-error TS(2532) FIXME: Object is possibly 'undefined'.
   const filesWithWarning = response.filter((el) => el.warning)
   filesWithWarning.forEach((el) => {
-    // @ts-expect-error TS(2532) FIXME: Object is possibly 'undefined'.
     warn(el.warning)
   })
 
-  // @ts-expect-error TS(2532) FIXME: Object is possibly 'undefined'.
-  return response.filter((el) => el.file && el.env)
+  return response.filter((result): result is { file: string; env: dotenv.DotenvParseOutput } =>
+    Boolean(result.file && result.env),
+  )
 }
 
 // in the user configuration, the order is highest to lowest
 const defaultEnvFiles = ['.env.development.local', '.env.local', '.env.development', '.env']
 
-// @ts-expect-error TS(7031) FIXME: Binding element 'projectDir' implicitly has an 'an... Remove this comment to see the full error message
-export const tryLoadDotEnvFiles = async ({ dotenvFiles = defaultEnvFiles, projectDir }) => {
+export const tryLoadDotEnvFiles = async ({
+  dotenvFiles = defaultEnvFiles,
+  projectDir,
+}: {
+  dotenvFiles?: string[]
+  projectDir: string
+}) => {
   const results = await Promise.all(
     dotenvFiles.map(async (file) => {
       const filepath = path.resolve(projectDir, file)
@@ -48,5 +51,5 @@ export const tryLoadDotEnvFiles = async ({ dotenvFiles = defaultEnvFiles, projec
   )
 
   // we return in order of lowest to highest priority
-  return results.filter(Boolean).reverse()
+  return results.filter((result): result is NonNullable<typeof result> => Boolean(result)).reverse()
 }

src/utils/shell.ts

@@ -2,7 +2,7 @@ import process from 'process'
 import { Transform } from 'stream'
 import { stripVTControlCharacters } from 'util'
 
-import execa from 'execa'
+import execa, { type ExecaError } from 'execa'
 
 import { type Spinner } from '../lib/spinner.js'
 
@@ -101,9 +101,7 @@ export const runCommand = (
       )
     } else {
       const errorMessage = result.failed
-        ? // @ts-expect-error FIXME(serhalp): We use `reject: false` which means the resolved value is either the resolved value
-          // or the rejected value, but the types aren't smart enough to know this.
-          `${NETLIFYDEVERR} ${result.shortMessage as string}`
+        ? `${NETLIFYDEVERR} ${(result as ExecaError).shortMessage}`
         : `${NETLIFYDEVWARN} "${command}" exited with code ${result.exitCode.toString()}`
 
       log(`${errorMessage}. Shutting down Netlify Dev server`)