util: add exec command for arbitrary aliases

CHANGELOG.md

@@ -20,6 +20,8 @@ to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 * The `jj desc` and `jj st` aliases are now hidden to not interfere with shell
   completion. They remain available.
 
+* New command `jj util exec` that can be used for arbitrary aliases.
+
 ### Fixed bugs
 
 ## [0.23.0] - 2024-11-06

cli/src/commands/util/exec.rs

@@ -0,0 +1,95 @@
+// Copyright 2024 The Jujutsu Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use crate::cli_util::CommandHelper;
+use crate::command_error::user_error;
+use crate::command_error::user_error_with_message;
+use crate::command_error::CommandError;
+use crate::ui::Ui;
+
+/// Execute an external command via jj
+///
+/// This is useful for arbitrary aliases.
+///
+/// !! WARNING !!
+///
+/// The following technique just provides a convenient syntax for running
+/// arbitrary code on your system. Using it irresponsibly may cause damage
+/// ranging from breaking the behavior of `jj undo` to wiping your file system.
+/// Exercise the same amount of caution while writing these aliases as you would
+/// when typing commands into the terminal!
+///
+/// This feature may be removed entirely in the future. It may be replaced by
+/// an embedded scripting language with limited capabilities for safety.
+///
+/// Let's assume you have a script called "my-jj-script" in you $PATH and you
+/// would like to execute it as "jj my-script". You would add the following line
+/// to your configuration file to achieve that:
+///
+/// ```toml
+/// [aliases]
+/// my-script = ["util", "exec", "--", "my-jj-script"]
+/// #                            ^^^^
+/// # This makes sure that flags are passed to your script instead of parsed by jj.
+/// ```
+///
+/// If you don't want to manage your script as a separate file, you can even
+/// inline it into your config file:
+///
+/// ```toml
+/// [aliases]
+/// my-inline-script = ["util", "exec", "--", "bash", "-c", """
+/// #!/usr/bin/env bash
+/// set -euo pipefail
+/// echo "Look Ma, everything in one file!"
+/// echo "args: $@"
+/// """, ""]
+/// #    ^^
+/// # This last empty string will become "$0" in bash, so your actual arguments
+/// # are all included in "$@" and start at "$1" as expected.
+/// ```
+#[derive(clap::Args, Clone, Debug)]
+#[command(verbatim_doc_comment)]
+pub(crate) struct UtilExecArgs {
+    /// External command to execute
+    command: String,
+    /// Arguments to pass to the external command
+    args: Vec<String>,
+}
+
+pub fn cmd_util_exec(
+    _ui: &mut Ui,
+    _command: &CommandHelper,
+    args: &UtilExecArgs,
+) -> Result<(), CommandError> {
+    let status = std::process::Command::new(&args.command)
+        .args(&args.args)
+        .status()
+        .map_err(|err| {
+            user_error_with_message(
+                format!("Failed to execute external command '{}'", &args.command),
+                err,
+            )
+        })?;
+    if !status.success() {
+        let error_msg = if let Some(exit_code) = status.code() {
+            format!("External command exited with {exit_code}")
+        } else {
+            // signal
+            format!("External command was terminated by: {status}")
+        };
+        return Err(user_error(error_msg));
+    }
+    Ok(())
+}

cli/src/commands/util/mod.rs

@@ -14,6 +14,7 @@
 
 mod completion;
 mod config_schema;
+mod exec;
 mod gc;
 mod mangen;
 mod markdown_help;
@@ -25,6 +26,8 @@ use self::completion::cmd_util_completion;
 use self::completion::UtilCompletionArgs;
 use self::config_schema::cmd_util_config_schema;
 use self::config_schema::UtilConfigSchemaArgs;
+use self::exec::cmd_util_exec;
+use self::exec::UtilExecArgs;
 use self::gc::cmd_util_gc;
 use self::gc::UtilGcArgs;
 use self::mangen::cmd_util_mangen;
@@ -40,6 +43,7 @@ use crate::ui::Ui;
 pub(crate) enum UtilCommand {
     Completion(UtilCompletionArgs),
     ConfigSchema(UtilConfigSchemaArgs),
+    Exec(UtilExecArgs),
     Gc(UtilGcArgs),
     Mangen(UtilMangenArgs),
     MarkdownHelp(UtilMarkdownHelp),
@@ -54,6 +58,7 @@ pub(crate) fn cmd_util(
     match subcommand {
         UtilCommand::Completion(args) => cmd_util_completion(ui, command, args),
         UtilCommand::ConfigSchema(args) => cmd_util_config_schema(ui, command, args),
+        UtilCommand::Exec(args) => cmd_util_exec(ui, command, args),
         UtilCommand::Gc(args) => cmd_util_gc(ui, command, args),
         UtilCommand::Mangen(args) => cmd_util_mangen(ui, command, args),
         UtilCommand::MarkdownHelp(args) => cmd_util_markdown_help(ui, command, args),

cli/tests/cli-reference@.md.snap

@@ -92,6 +92,7 @@ This document contains the help content for the `jj` command-line program.
 * [`jj util`↴](#jj-util)
 * [`jj util completion`↴](#jj-util-completion)
 * [`jj util config-schema`↴](#jj-util-config-schema)
+* [`jj util exec`↴](#jj-util-exec)
 * [`jj util gc`↴](#jj-util-gc)
 * [`jj util mangen`↴](#jj-util-mangen)
 * [`jj util markdown-help`↴](#jj-util-markdown-help)
@@ -2117,6 +2118,7 @@ Infrequently used commands such as for generating shell completions
 
 * `completion` — Print a command-line-completion script
 * `config-schema` — Print the JSON schema for the jj TOML config format
+* `exec` — Execute an external command via jj
 * `gc` — Run backend-dependent garbage collection
 * `mangen` — Print a ROFF (manpage)
 * `markdown-help` — Print the CLI help for all subcommands in Markdown
@@ -2162,6 +2164,59 @@ Print the JSON schema for the jj TOML config format
 
 
 
+## `jj util exec`
+
+Execute an external command via jj
+
+This is useful for arbitrary aliases.
+
+!! WARNING !!
+
+The following technique just provides a convenient syntax for running
+arbitrary code on your system. Using it irresponsibly may cause damage
+ranging from breaking the behavior of `jj undo` to wiping your file system.
+Exercise the same amount of caution while writing these aliases as you would
+when typing commands into the terminal!
+
+This feature may be removed entirely in the future. It may be replaced by
+an embedded scripting language with limited capabilities for safety.
+
+Let's assume you have a script called "my-jj-script" in you $PATH and you
+would like to execute it as "jj my-script". You would add the following line
+to your configuration file to achieve that:
+
+```toml
+[aliases]
+my-script = ["util", "exec", "--", "my-jj-script"]
+#                            ^^^^
+# This makes sure that flags are passed to your script instead of parsed by jj.
+```
+
+If you don't want to manage your script as a separate file, you can even
+inline it into your config file:
+
+```toml
+[aliases]
+my-inline-script = ["util", "exec", "--", "bash", "-c", """
+#!/usr/bin/env bash
+set -euo pipefail
+echo "Look Ma, everything in one file!"
+echo "args: $@"
+""", ""]
+#    ^^
+# This last empty string will become "$0" in bash, so your actual arguments
+# are all included in "$@" and start at "$1" as expected.
+```
+
+**Usage:** `jj util exec <COMMAND> [ARGS]...`
+
+###### **Arguments:**
+
+* `<COMMAND>` — External command to execute
+* `<ARGS>` — Arguments to pass to the external command
+
+
+
 ## `jj util gc`
 
 Run backend-dependent garbage collection

cli/tests/test_util_command.rs

@@ -14,6 +14,7 @@
 
 use insta::assert_snapshot;
 
+use crate::common::strip_last_line;
 use crate::common::TestEnvironment;
 
 #[test]
@@ -112,3 +113,33 @@ fn test_shell_completions() {
     test("nushell");
     test("zsh");
 }
+
+#[test]
+fn test_util_exec() {
+    let test_env = TestEnvironment::default();
+    let formatter_path = assert_cmd::cargo::cargo_bin("fake-formatter");
+    let (out, err) = test_env.jj_cmd_ok(
+        test_env.env_root(),
+        &[
+            "util",
+            "exec",
+            "--",
+            formatter_path.to_str().unwrap(),
+            "--append",
+            "hello",
+        ],
+    );
+    insta::assert_snapshot!(out, @"hello");
+    // Ensures only stdout contains text
+    assert!(err.is_empty());
+}
+
+#[test]
+fn test_util_exec_fail() {
+    let test_env = TestEnvironment::default();
+    let err = test_env.jj_cmd_failure(
+        test_env.env_root(),
+        &["util", "exec", "--", "missing-program"],
+    );
+    insta::assert_snapshot!(strip_last_line(&err), @"Error: Failed to execute external command 'missing-program'");
+}

docs/config.md

@@ -528,6 +528,41 @@ You can define aliases for commands, including their arguments. For example:
 aliases.l = ["log", "-r", "(main..@):: | (main..@)-"]
 ```
 
+This alias syntax can only run a single jj command. However, you may want to
+execute multiple jj commands with a single alias, or run arbitrary scripts that
+complement your version control workflow. This can be done, but be aware of the
+danger:
+
+!!! warning
+
+    The following technique just provides a convenient syntax for running
+    arbitrary code on your system. Using it irresponsibly may cause damage
+    ranging from breaking the behavior of `jj undo` to wiping your file system.
+    Exercise the same amount of caution while writing these aliases as you would
+    when typing commands into the terminal!
+
+    This feature may be removed entirely in the future. It may be replaced by
+    an embedded scripting language with limited capabilities for safety.
+
+The command `jj util exec` will simply run any command you pass to it as an
+argument. Additional arguments are passed through. Here are some examples:
+
+```toml
+[aliases]
+my-script = ["util", "exec", "--", "my-jj-script"]
+#                            ^^^^
+# This makes sure that flags are passed to your script instead of parsed by jj.
+my-inline-script = ["util", "exec", "--", "bash", "-c", """
+#!/usr/bin/env bash
+set -euo pipefail
+echo "Look Ma, everything in one file!"
+echo "args: $@"
+""", ""]
+#    ^^
+# This last empty string will become "$0" in bash, so your actual arguments
+# are all included in "$@" and start at "$1" as expected.
+```
+
 ## Editor
 
 The default editor is set via `ui.editor`, though there are several places to