init

src/start.ts

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+import yargs from 'yargs/yargs';
+import { hideBin } from 'yargs/helpers';
+
+import { exec } from './utils/exec.js';
+import { getEnv } from './utils/env.js';
+import { replaceParams } from './utils/ssm.js';
+
+const argv = await yargs(hideBin(process.argv))
+  .usage('Usage: $0 [options] -- <command>')
+  .option('region', {
+    type: 'string',
+    description: 'The AWS region to use for SSM.',
+  })
+  .option('profile', {
+    type: 'string',
+    description: 'The AWS profile to use from your credentials file.',
+  })
+  .option('file', {
+    alias: 'f',
+    type: 'string',
+    description: 'The file to use for environment variables. (multiple files can be specified)',
+    default: ['.env', '.env.with-ssm'],
+  })
+  .demandCommand(1, 'Error: You must provide a command to execute after --')
+  .alias('h', 'help')
+  .epilogue('For more information, check the documentation.')
+  .parse();
+
+const command = argv._[0] as string;
+const commandArgs = argv._.slice(1).map(String);
+
+if (!command) {
+  console.error('No command provided');
+  process.exit(1);
+}
+
+const files = argv.file && Array.isArray(argv.file) ? argv.file : [argv.file];
+const hostEnv = await getEnv(files);
+const env = await replaceParams(hostEnv);
+
+exec({
+  command,
+  env,
+  args: commandArgs,
+});

src/utils/cli.ts

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+const splitArgs = (args: string[]) => {
+  const separatorIndex = args.indexOf('--');
+  const actionArgs = args.slice(0, separatorIndex);
+  const command = args[separatorIndex + 1];
+  const commandArgs = args.slice(separatorIndex + 2);
+
+  return {
+    actionArgs,
+    command,
+    commandArgs,
+  };
+};
+
+export { splitArgs };

src/utils/debug.ts

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+import { debuglog } from 'node:util';
+
+const debug = debuglog('with-ssm');
+
+export { debug };

src/utils/env.ts

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+import { existsSync } from 'node:fs';
+import { readFile } from 'node:fs/promises';
+import { resolve } from 'node:path';
+
+import { parse } from 'dotenv';
+
+import { debug } from './debug.js';
+
+const getEnv = async (files: string[]) => {
+  const env = { ...process.env };
+
+  for (const file of files) {
+    if (existsSync(resolve(process.cwd(), file))) {
+      debug(`Loading ${file}`);
+      const content = await readFile(file, 'utf8');
+      const parsed = parse(content);
+      debug(`Parsed ${file}\n${JSON.stringify(parsed, null, 2)}`);
+      Object.assign(env, parsed);
+    }
+  }
+
+  return env;
+};
+
+export { getEnv };

src/utils/exec.ts

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+import { spawn } from 'child_process';
+
+type ExecOptions = {
+  command: string;
+  args: string[];
+  cwd?: string;
+  env?: Record<string, string | undefined>;
+};
+
+const exec = (options: ExecOptions) => {
+  const { command, args, cwd, env } = options;
+  const child = spawn(command, args, { cwd, env, stdio: 'inherit' });
+  const killChild = () => child.kill();
+
+  process.on('SIGINT', killChild);
+  process.on('SIGTERM', killChild);
+  child.on('exit', (code) => {
+    process.exit(code ?? 1);
+  });
+
+  child.on('error', (err) => {
+    console.error(`[with-ssm] ❌ Failed to start command "${command}".`);
+    console.error(err.message);
+    process.exit(1);
+  });
+
+  return child;
+};
+
+export { exec };

src/utils/ssm.ts

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+import { GetParametersCommand, SSMClient } from '@aws-sdk/client-ssm';
+
+import { debug } from './debug.js';
+
+const PREFIX = 'SSM:';
+
+type ReplaceParamsOptions = {
+  region?: string;
+  profile?: string;
+};
+
+const replaceParams = async (
+  env: Record<string, string | undefined>,
+  { region, profile }: ReplaceParamsOptions = {},
+) => {
+  const ssm = new SSMClient({
+    region,
+    profile,
+  });
+
+  const names = Object.entries(env)
+    .filter(([, value]) => value?.startsWith(PREFIX))
+    .map(([, value]) => value?.slice(PREFIX.length))
+    .filter((value) => value !== undefined);
+
+  debug(`Replacing ${names.length} parameters`);
+  debug(`Names: ${names.join(', ')}`);
+
+  if (names.length === 0) {
+    return env;
+  }
+
+  const command = new GetParametersCommand({
+    Names: names,
+    WithDecryption: true,
+  });
+
+  const response = await ssm.send(command);
+  if (response.InvalidParameters?.length || 0 > 0) {
+    console.error('Invalid SSM parameters', response.InvalidParameters);
+    process.exit(1);
+  }
+
+  const params = response.Parameters ?? [];
+
+  return Object.fromEntries(
+    Object.entries(env).map(([key, value]) => {
+      if (value?.startsWith(PREFIX)) {
+        const param = params.find((param) => `SSM:${param.Name}` === value);
+        debug(`Replacing ${key} with ${param?.Value}`);
+        return [key, param?.Value];
+      }
+
+      return [key, value];
+    }),
+  );
+};
+
+export { replaceParams };