Initial envsitter CLI and safe env matching

src/sources/dotenvFile.ts

@@ -0,0 +1,32 @@
+import { readFile } from 'node:fs/promises';
+import { parseDotenv } from '../dotenv/parse.js';
+
+export type DotenvFileSourceOptions = {
+  allowErrors?: boolean;
+};
+
+type Snapshot = {
+  values: ReadonlyMap<string, string>;
+};
+
+export class DotenvFileSource {
+  readonly filePath: string;
+  readonly options: DotenvFileSourceOptions;
+
+  constructor(filePath: string, options: DotenvFileSourceOptions = {}) {
+    this.filePath = filePath;
+    this.options = options;
+  }
+
+  async load(): Promise<Snapshot> {
+    const contents = await readFile(this.filePath, 'utf8');
+    const parsed = parseDotenv(contents);
+
+    if (parsed.errors.length > 0 && !this.options.allowErrors) {
+      const message = parsed.errors.map((e) => `L${e.line}: ${e.message}`).join(', ');
+      throw new Error(`Invalid dotenv file: ${message}`);
+    }
+
+    return { values: parsed.values };
+  }
+}

src/sources/externalCommand.ts

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+import { execFile } from 'node:child_process';
+import { promisify } from 'node:util';
+import { parseDotenv } from '../dotenv/parse.js';
+
+const execFileAsync = promisify(execFile);
+
+type Snapshot = {
+  values: ReadonlyMap<string, string>;
+};
+
+export type ExternalCommandSourceOptions = {
+  cwd?: string;
+  env?: NodeJS.ProcessEnv;
+  timeoutMs?: number;
+  allowErrors?: boolean;
+};
+
+export class ExternalCommandSource {
+  readonly command: string;
+  readonly args: readonly string[];
+  readonly options: ExternalCommandSourceOptions;
+
+  constructor(command: string, args: readonly string[] = [], options: ExternalCommandSourceOptions = {}) {
+    this.command = command;
+    this.args = args;
+    this.options = options;
+  }
+
+  async load(): Promise<Snapshot> {
+    const { stdout } = await execFileAsync(this.command, [...this.args], {
+      cwd: this.options.cwd,
+      env: this.options.env,
+      timeout: this.options.timeoutMs
+    });
+
+    const parsed = parseDotenv(stdout);
+
+    if (parsed.errors.length > 0 && !this.options.allowErrors) {
+      const message = parsed.errors.map((e) => `L${e.line}: ${e.message}`).join(', ');
+      throw new Error(`Invalid dotenv content from external command: ${message}`);
+    }
+
+    return { values: parsed.values };
+  }
+}