feat: add unset command and fix VAR= behaviour

README.md

@@ -722,6 +722,7 @@ Currently implemented (though not every option is supported):
 - [`sleep`](https://man7.org/linux/man-pages/man1/sleep.1.html) - Sleep command.
 - [`test`](https://man7.org/linux/man-pages/man1/test.1.html) - Test command.
 - [`touch`](https://man7.org/linux/man-pages/man1/touch.1.html) - Creates a file (note: flags have not been implemented yet).
+- [`unset`](https://man7.org/linux/man-pages/man1/unset.1p.html) - Unsets an environment variable.
 - More to come. Will try to get a similar list as https://deno.land/manual/tools/task_runner#built-in-commands
 
 You can also register your own commands with the shell parser (see below).

mod.test.ts

@@ -602,6 +602,41 @@ Deno.test("exporting env should modify real environment when something changed v
   }
 });
 
+Deno.test("setting an empty env var should work", async () => {
+  const text = await $`VAR= deno eval 'console.log("VAR: " + Deno.env.get("VAR"))'`.text();
+  assertEquals(text, "VAR: ");
+});
+
+Deno.test("unsetting env var should work", async () => {
+  const text = await $`unset VAR && deno eval 'console.log("VAR: " + Deno.env.get("VAR"))'`
+    .env("VAR", "1")
+    .text();
+  assertEquals(text, "VAR: undefined");
+});
+
+Deno.test("unsetting multiple env vars should work", async () => {
+  const text =
+    await $`unset VAR1 VAR2 && deno eval 'console.log("VAR: " + Deno.env.get("VAR1") + Deno.env.get("VAR2") + Deno.env.get("VAR3"))'`
+      .env({
+        "VAR1": "test",
+        "VAR2": "test",
+        "VAR3": "test",
+      })
+      .text();
+  assertEquals(text, "VAR: undefinedundefinedtest");
+});
+
+Deno.test("unset with -f should error", async () => {
+  const result = await $`unset -f VAR1 && echo $VAR1`
+    .env({ "VAR1": "test" })
+    .stdout("piped")
+    .stderr("piped")
+    .noThrow();
+  assertEquals(result.code, 1);
+  assertEquals(result.stderr, "unset: unsupported flag: -f\n");
+  assertEquals(result.stdout, "");
+});
+
 Deno.test("cwd should be resolved based on cwd at time of method call and not execution", async () => {
   const previousCwd = Deno.cwd();
   try {

src/command.ts

@@ -1,5 +1,6 @@
 import { CommandHandler } from "./command_handler.ts";
 import { cdCommand } from "./commands/cd.ts";
+import { cpCommand, mvCommand } from "./commands/cp_mv.ts";
 import { echoCommand } from "./commands/echo.ts";
 import { exitCommand } from "./commands/exit.ts";
 import { exportCommand } from "./commands/export.ts";
@@ -8,6 +9,8 @@ import { rmCommand } from "./commands/rm.ts";
 import { pwdCommand } from "./commands/pwd.ts";
 import { sleepCommand } from "./commands/sleep.ts";
 import { testCommand } from "./commands/test.ts";
+import { touchCommand } from "./commands/touch.ts";
+import { unsetCommand } from "./commands/unset.ts";
 import { Box, delayToMs, LoggerTreeBox } from "./common.ts";
 import { Delay } from "./common.ts";
 import { Buffer, colors, path, readerFromStreamReader } from "./deps.ts";
@@ -21,9 +24,7 @@ import {
   ShellPipeWriterKind,
 } from "./pipes.ts";
 import { parseCommand, spawn } from "./shell.ts";
-import { cpCommand, mvCommand } from "./commands/cp_mv.ts";
 import { isShowingProgressBars } from "./console/progress/interval.ts";
-import { touchCommand } from "./commands/touch.ts";
 import { PathRef } from "./path.ts";
 
 type BufferStdio = "inherit" | "null" | "streamed" | Buffer;
@@ -59,6 +60,7 @@ const builtInCommands = {
   mv: mvCommand,
   pwd: pwdCommand,
   touch: touchCommand,
+  unset: unsetCommand,
 };
 
 /** @internal */

src/commands/cd.ts

@@ -14,7 +14,7 @@ export async function cdCommand(context: CommandContext): Promise<ExecuteResult>
       }],
     };
   } catch (err) {
-    await context.stderr.writeLine(`cd: ${err?.message ?? err}`);
+    context.stderr.writeLine(`cd: ${err?.message ?? err}`);
     return resultFromCode(1);
   }
 }

src/commands/echo.ts

@@ -1,7 +1,7 @@
 import { CommandContext } from "../command_handler.ts";
 import { ExecuteResult, resultFromCode } from "../result.ts";
 
-export async function echoCommand(context: CommandContext): Promise<ExecuteResult> {
-  await context.stdout.writeLine(context.args.join(" "));
+export function echoCommand(context: CommandContext): ExecuteResult {
+  context.stdout.writeLine(context.args.join(" "));
   return resultFromCode(0);
 }

src/commands/exit.ts

@@ -1,15 +1,15 @@
 import { CommandContext } from "../command_handler.ts";
 import { ExitExecuteResult } from "../result.ts";
 
-export async function exitCommand(context: CommandContext): Promise<ExitExecuteResult> {
+export function exitCommand(context: CommandContext): ExitExecuteResult {
   try {
     const code = parseArgs(context.args);
     return {
       kind: "exit",
       code,
     };
   } catch (err) {
-    await context.stderr.writeLine(`exit: ${err?.message ?? err}`);
+    context.stderr.writeLine(`exit: ${err?.message ?? err}`);
     // impl. note: bash returns 2 on exit parse failure, deno_task_shell returns 1
     return {
       kind: "exit",

src/commands/sleep.ts

@@ -19,7 +19,7 @@ export async function sleepCommand(context: CommandContext): Promise<ExecuteResu
     }
     return resultFromCode(0);
   } catch (err) {
-    await context.stderr.writeLine(`sleep: ${err?.message ?? err}`);
+    context.stderr.writeLine(`sleep: ${err?.message ?? err}`);
     return resultFromCode(1);
   }
 }

src/commands/test.ts

@@ -33,7 +33,7 @@ export async function testCommand(context: CommandContext): Promise<ExecuteResul
     }
     return resultFromCode(result ? 0 : 1);
   } catch (err) {
-    await context.stderr.writeLine(`test: ${err?.message ?? err}`);
+    context.stderr.writeLine(`test: ${err?.message ?? err}`);
     // bash test returns 2 on error, e.g. -bash: test: -8: unary operator expected
     return resultFromCode(2);
   }

src/commands/unset.ts

@@ -0,0 +1,27 @@
+import { ExecuteResult } from "../../mod.ts";
+import { CommandContext } from "../command_handler.ts";
+import { resultFromCode } from "../result.ts";
+
+export function unsetCommand(context: CommandContext): ExecuteResult {
+  try {
+    return {
+      kind: "continue",
+      code: 0,
+      changes: parseNames(context.args).map((name) => ({ kind: "unsetvar", name })),
+    };
+  } catch (err) {
+    context.stderr.writeLine(`unset: ${err?.message ?? err}`);
+    return resultFromCode(1);
+  }
+}
+
+function parseNames(args: string[]) {
+  if (args[0] === "-f") {
+    // we don't support the -f (function) flag
+    throw Error(`unsupported flag: -f`);
+  } else if (args[0] === "-v") {
+    return args.slice(1);
+  } else {
+    return args;
+  }
+}

src/result.ts

@@ -32,7 +32,7 @@ export interface ContinueExecuteResult {
  *
  * Used for registering custom commands.
  */
-export type EnvChange = SetEnvVarChange | SetShellVarChange | CdChange;
+export type EnvChange = SetEnvVarChange | SetShellVarChange | UnsetVarChange | CdChange;
 
 /** Change that sets an environment variable (ex. `export ENV_VAR=VALUE`)
  *
@@ -54,6 +54,15 @@ export interface SetShellVarChange {
   value: string;
 }
 
+/** Change that deletes the environment variable (ex. `unset ENV_VAR`).
+ *
+ * Used for registering custom commands.
+ */
+export interface UnsetVarChange {
+  kind: "unsetvar";
+  name: string;
+}
+
 /** Change that alters the current working directory.
  *
  * Used for registering custom commands.

src/shell.ts

@@ -159,7 +159,7 @@ class ShellEnv implements Env {
     if (Deno.build.os === "windows") {
       key = key.toUpperCase();
     }
-    if (value == null || value.length === 0) {
+    if (value == null) {
       delete this.#envVars[key];
     } else {
       this.#envVars[key] = value;
@@ -244,6 +244,9 @@ export class Context {
         case "shellvar":
           this.setShellVar(change.name, change.value);
           break;
+        case "unsetvar":
+          this.setShellVar(change.name, undefined);
+          break;
         default: {
           const _assertNever: never = change;
           throw new Error(`Not implemented env change: ${change}`);