fix(custom): improve handling of Powershell prompts (#1237)

To improve overall support of PowerShell in custom modules,
the ability to pass arguments to the shell was also added. Additionally,
the arguments `-NoProfile -Command -` will be automatically passed
to PowerShell, unless other arguments are given by the user.

docs/config/README.md

@@ -1420,7 +1420,7 @@ will simply show all custom modules in the order they were defined.
 | ------------- | ------------------- | ---------------------------------------------------------------------------- |
 | `command`     |                     | The command whose output should be printed.                                  |
 | `when`        |                     | A shell command used as a condition to show the module. The module will be shown if the command returns a `0` status code. |
-| `shell`       |                     | The path to the shell to use to execute the command. If unset, it will fallback to STARSHIP_SHELL and then to "sh". |
+| `shell`       |                     | [See below](#custom-command-shell)                                           |
 | `description` | `"<custom module>"` | The description of the module that is shown when running `starship explain`. |
 | `files`       | `[]`                | The files that will be searched in the working directory for a match.        |
 | `directories` | `[]`                | The directories that will be searched in the working directory for a match.  |
@@ -1431,6 +1431,22 @@ will simply show all custom modules in the order they were defined.
 | `suffix`      | `""`                | Suffix to display immediately after the command output.                      |
 | `disabled`    | `false`             | Disables this `custom` module.                                               |
 
+#### Custom command shell
+
+`shell` accepts a non-empty list of strings, where:
+- The first string is the path to the shell to use to execute the command.
+- Other following arguments are passed to the shell.
+
+If unset, it will fallback to STARSHIP_SHELL and then to "sh" on Linux, and "cmd /C" on Windows.
+
+If `shell` is not given or only contains one element and Starship detects PowerShell will be used,
+the following arguments will automatically be added: `-NoProfile -Command -`.  
+This behavior can be avoided by explicitly passing arguments to the shell, e.g.
+
+```toml
+shell = ["pwsh", "-Command", "-"]
+```
+
 ### Example
 
 ```toml

src/config.rs

@@ -153,6 +153,30 @@ where
     }
 }
 
+/// A wrapper around `Vec<T>` that implements `ModuleConfig`, and either
+/// accepts a value of type `T` or a list of values of type `T`.
+#[derive(Clone, Default)]
+pub struct VecOr<T>(pub Vec<T>);
+
+impl<'a, T> ModuleConfig<'a> for VecOr<T>
+where
+    T: ModuleConfig<'a> + Sized,
+{
+    fn from_config(config: &'a Value) -> Option<Self> {
+        if let Some(item) = T::from_config(config) {
+            return Some(VecOr(vec![item]));
+        }
+
+        let vec = config
+            .as_array()?
+            .iter()
+            .map(|value| T::from_config(value))
+            .collect::<Option<Vec<T>>>()?;
+
+        Some(VecOr(vec))
+    }
+}
+
 /// Root config of starship.
 pub struct StarshipConfig {
     pub config: Option<Value>,

src/configs/custom.rs

@@ -1,4 +1,4 @@
-use crate::config::{ModuleConfig, RootModuleConfig, SegmentConfig};
+use crate::config::{ModuleConfig, RootModuleConfig, SegmentConfig, VecOr};
 
 use ansi_term::Style;
 use starship_module_config_derive::ModuleConfig;
@@ -17,7 +17,7 @@ pub struct CustomConfig<'a> {
     pub symbol: Option<SegmentConfig<'a>>,
     pub command: &'a str,
     pub when: Option<&'a str>,
-    pub shell: Option<&'a str>,
+    pub shell: VecOr<&'a str>,
     pub description: &'a str,
     pub style: Option<Style>,
     pub disabled: bool,
@@ -34,7 +34,7 @@ impl<'a> RootModuleConfig<'a> for CustomConfig<'a> {
             symbol: None,
             command: "",
             when: None,
-            shell: None,
+            shell: VecOr::default(),
             description: "<custom config>",
             style: None,
             disabled: false,

src/modules/custom.rs

@@ -35,7 +35,7 @@ pub fn module<'a>(name: &'a str, context: &'a Context) -> Option<Module<'a>> {
 
     if !is_match {
         if let Some(when) = config.when {
-            is_match = exec_when(when, config.shell);
+            is_match = exec_when(when, &config.shell.0);
         }
 
         if !is_match {
@@ -57,7 +57,7 @@ pub fn module<'a>(name: &'a str, context: &'a Context) -> Option<Module<'a>> {
         module.create_segment("symbol", &symbol);
     }
 
-    if let Some(output) = exec_command(config.command, config.shell) {
+    if let Some(output) = exec_command(config.command, &config.shell.0) {
         let trimmed = output.trim();
 
         if trimmed.is_empty() {
@@ -77,26 +77,31 @@ pub fn module<'a>(name: &'a str, context: &'a Context) -> Option<Module<'a>> {
 
 /// Return the invoking shell, using `shell` and fallbacking in order to STARSHIP_SHELL and "sh"
 #[cfg(not(windows))]
-fn get_shell(shell: Option<&str>) -> std::borrow::Cow<str> {
-    if let Some(forced_shell) = shell {
-        forced_shell.into()
+fn get_shell<'a, 'b>(shell_args: &'b [&'a str]) -> (std::borrow::Cow<'a, str>, &'b [&'a str]) {
+    if !shell_args.is_empty() {
+        (shell_args[0].into(), &shell_args[1..])
     } else if let Ok(env_shell) = std::env::var("STARSHIP_SHELL") {
-        env_shell.into()
+        (env_shell.into(), &[] as &[&str])
     } else {
-        "sh".into()
+        ("sh".into(), &[] as &[&str])
     }
 }
 
 /// Attempt to run the given command in a shell by passing it as `stdin` to `get_shell()`
 #[cfg(not(windows))]
-fn shell_command(cmd: &str, shell: Option<&str>) -> Option<Output> {
-    let command = Command::new(get_shell(shell).as_ref())
+fn shell_command(cmd: &str, shell_args: &[&str]) -> Option<Output> {
+    let (shell, shell_args) = get_shell(shell_args);
+    let mut command = Command::new(shell.as_ref());
+
+    command
+        .args(shell_args)
         .stdin(Stdio::piped())
         .stdout(Stdio::piped())
-        .stderr(Stdio::piped())
-        .spawn();
+        .stderr(Stdio::piped());
 
-    let mut child = match command {
+    handle_powershell(&mut command, &shell, shell_args);
+
+    let mut child = match command.spawn() {
         Ok(command) => command,
         Err(_) => {
             log::debug!(
@@ -120,23 +125,30 @@ fn shell_command(cmd: &str, shell: Option<&str>) -> Option<Output> {
 /// Attempt to run the given command in a shell by passing it as `stdin` to `get_shell()`,
 /// or by invoking cmd.exe /C.
 #[cfg(windows)]
-fn shell_command(cmd: &str, shell: Option<&str>) -> Option<Output> {
-    let shell = if let Some(shell) = shell {
-        Some(std::borrow::Cow::Borrowed(shell))
+fn shell_command(cmd: &str, shell_args: &[&str]) -> Option<Output> {
+    let (shell, shell_args) = if !shell_args.is_empty() {
+        (
+            Some(std::borrow::Cow::Borrowed(shell_args[0])),
+            &shell_args[1..],
+        )
     } else if let Ok(env_shell) = std::env::var("STARSHIP_SHELL") {
-        Some(std::borrow::Cow::Owned(env_shell))
+        (Some(std::borrow::Cow::Owned(env_shell)), &[] as &[&str])
     } else {
-        None
+        (None, &[] as &[&str])
     };
 
     if let Some(forced_shell) = shell {
-        let command = Command::new(forced_shell.as_ref())
+        let mut command = Command::new(forced_shell.as_ref());
+
+        command
+            .args(shell_args)
             .stdin(Stdio::piped())
             .stdout(Stdio::piped())
-            .stderr(Stdio::piped())
-            .spawn();
+            .stderr(Stdio::piped());
 
-        if let Ok(mut child) = command {
+        handle_powershell(&mut command, &forced_shell, shell_args);
+
+        if let Ok(mut child) = command.spawn() {
             child.stdin.as_mut()?.write_all(cmd.as_bytes()).ok()?;
 
             return child.wait_with_output().ok();
@@ -159,10 +171,10 @@ fn shell_command(cmd: &str, shell: Option<&str>) -> Option<Output> {
 }
 
 /// Execute the given command capturing all output, and return whether it return 0
-fn exec_when(cmd: &str, shell: Option<&str>) -> bool {
+fn exec_when(cmd: &str, shell_args: &[&str]) -> bool {
     log::trace!("Running '{}'", cmd);
 
-    if let Some(output) = shell_command(cmd, shell) {
+    if let Some(output) = shell_command(cmd, shell_args) {
         if !output.status.success() {
             log::trace!("non-zero exit code '{:?}'", output.status.code());
             log::trace!(
@@ -184,10 +196,10 @@ fn exec_when(cmd: &str, shell: Option<&str>) -> bool {
 }
 
 /// Execute the given command, returning its output on success
-fn exec_command(cmd: &str, shell: Option<&str>) -> Option<String> {
+fn exec_command(cmd: &str, shell_args: &[&str]) -> Option<String> {
     log::trace!("Running '{}'", cmd);
 
-    if let Some(output) = shell_command(cmd, shell) {
+    if let Some(output) = shell_command(cmd, shell_args) {
         if !output.status.success() {
             log::trace!("Non-zero exit code '{:?}'", output.status.code());
             log::trace!(
@@ -207,14 +219,27 @@ fn exec_command(cmd: &str, shell: Option<&str>) -> Option<String> {
     }
 }
 
+/// If the specified shell refers to PowerShell, adds the arguments "-Command -" to the
+/// given command.
+fn handle_powershell(command: &mut Command, shell: &str, shell_args: &[&str]) {
+    let is_powershell = shell.ends_with("pwsh.exe")
+        || shell.ends_with("powershell.exe")
+        || shell.ends_with("pwsh")
+        || shell.ends_with("powershell");
+
+    if is_powershell && shell_args.is_empty() {
+        command.arg("-NoProfile").arg("-Command").arg("-");
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
 
     #[cfg(not(windows))]
-    const SHELL: Option<&'static str> = Some("/bin/sh");
+    const SHELL: &[&str] = &["/bin/sh"];
     #[cfg(windows)]
-    const SHELL: Option<&'static str> = None;
+    const SHELL: &[&str] = &[];
 
     #[cfg(not(windows))]
     const FAILING_COMMAND: &str = "false";