feat: add hostname module (#286)

Add a hostname module as requested by @chipbuster.
Displays the system hostname as provided by gethostname.

8 files changed, 198 insertions, 0 deletions

diff --git a/Cargo.lock b/Cargo.lock
index e6726b9a0..5bde96f65 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -280,6 +280,15 @@ version = "0.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
+name = "gethostname"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "libc 0.2.58 (registry+https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
 name = "getrandom"
 version = "0.1.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -745,6 +754,7 @@ dependencies = [
  "battery 0.7.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "clap 2.33.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "dirs 2.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "gethostname 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "git2 0.10.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -998,6 +1008,7 @@ dependencies = [
 "checksum failure 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "795bd83d3abeb9220f257e597aa0080a508b27533824adf336529648f6abf7e2"
 "checksum failure_derive 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "ea1063915fd7ef4309e222a5a07cf9c319fb9c7836b1f89b85458672dbb127e1"
 "checksum fuchsia-cprng 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "a06f77d526c1a601b7c4cdd98f54b5eaabffc14d5f2f0296febdc7f357c6d3ba"
+"checksum gethostname 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "d4ab273ca2a31eb6ca40b15837ccf1aa59a43c5db69ac10c542be342fae2e01d"
 "checksum getrandom 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)" = "e65cce4e5084b14874c4e7097f38cab54f47ee554f9194673456ea379dcc4c55"
 "checksum git2 0.10.0 (registry+https://github.com/rust-lang/crates.io-index)" = "327d698f86a7ebdfeb86a4238ccdb004828939d3a3555b6ead679541d14e36c0"
 "checksum humantime 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "3ca7e5f2e110db35f93b837c81797f3714500b81d517bf20c431b16d3ca4f114"
diff --git a/Cargo.toml b/Cargo.toml
index 52d83d774..65b976ceb 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -40,6 +40,7 @@ battery = { version = "0.7.4", optional = true }
 lazy_static = "1.4.0"
 path-slash = "0.1.1"
 unicode-segmentation = "1.3.0"
+gethostname = "0.2.0"
 
 [dev-dependencies]
 tempfile = "3.1.0"
diff --git a/docs/config/README.md b/docs/config/README.md
index 732e1528d..e7e8e5f4b 100644
--- a/docs/config/README.md
+++ b/docs/config/README.md
@@ -69,6 +69,7 @@ The `default_prompt_order` configuration option is used to define the order in w
 ```
 default_prompt_order = [
     "username",
+    "hostname",
     "directory",
     "git_branch",
     "git_status",
@@ -268,6 +269,31 @@ renamed = "👅"
 deleted = "🗑"
 ```
 
+## Hostname
+
+The `hostname` module shows the system hostname.
+
+### Options
+
+| Variable     | Default | Description                                             |
+| ------------ | ------- | ------------------------------------------------------- |
+| `ssh_only`   | `true`  | Only show hostname when connected to an SSH session.    |
+| `prefix`     | `""`    | Prefix to display immediately before the hostname.      |
+| `suffix`     | `""`    | Suffix to display immediately after the hostname.       |
+| `disabled`   | `false` | Disables the `hostname` module.                         |
+
+### Example
+
+```toml
+# ~/.config/starship.toml
+
+[hostname]
+ssh_only = false
+prefix = "⟪"
+suffix = "⟫"
+disabled = false
+```
+
 ## Golang
 
 The `golang` module shows the currently installed version of Golang.
diff --git a/src/modules/hostname.rs b/src/modules/hostname.rs
new file mode 100644
index 000000000..51567bcbb
--- /dev/null
+++ b/src/modules/hostname.rs
@@ -0,0 +1,39 @@
+use ansi_term::{Color, Style};
+use std::env;
+use std::process::Command;
+
+use super::{Context, Module};
+use std::ffi::OsString;
+
+/// Creates a module with the system hostname
+///
+/// Will display the hostname if all of the following criteria are met:
+///     - hostname.disabled is absent or false
+///     - hostname.ssh_only is false OR the user is currently connected as an SSH session (`$SSH_CONNECTION`)
+pub fn module<'a>(context: &'a Context) -> Option<Module<'a>> {
+    let mut module = context.new_module("hostname")?;
+
+    let ssh_connection = env::var("SSH_CONNECTION").ok();
+    if module.config_value_bool("ssh_only").unwrap_or(true) && ssh_connection.is_none() {
+        return None;
+    }
+
+    let os_hostname: OsString = gethostname::gethostname();
+
+    let host = match os_hostname.into_string() {
+        Ok(host) => host,
+        Err(bad) => {
+            log::debug!("hostname is not valid UTF!\n{:?}", bad);
+            return None;
+        }
+    };
+
+    let prefix = module.config_value_str("prefix").unwrap_or("").to_owned();
+    let suffix = module.config_value_str("suffix").unwrap_or("").to_owned();
+
+    module.set_style(Color::Green.bold().dimmed());
+    module.new_segment("hostname", &format!("{}{}{}", prefix, host, suffix));
+    module.get_prefix().set_value("on ");
+
+    Some(module)
+}
diff --git a/src/modules/mod.rs b/src/modules/mod.rs
index 6c6861efe..23d82601f 100644
--- a/src/modules/mod.rs
+++ b/src/modules/mod.rs
@@ -5,6 +5,7 @@ mod directory;
 mod git_branch;
 mod git_status;
 mod golang;
+mod hostname;
 mod jobs;
 mod line_break;
 mod nix_shell;
@@ -40,6 +41,7 @@ pub fn handle<'a>(module: &str, context: &'a Context) -> Option<Module<'a>> {
         "cmd_duration" => cmd_duration::module(context),
         "jobs" => jobs::module(context),
         "nix_shell" => nix_shell::module(context),
+        "hostname" => hostname::module(context),
 
         _ => {
             eprintln!("Error: Unknown module {}. Use starship module --list to list out all supported modules.", module);
diff --git a/src/print.rs b/src/print.rs
index c3d2e8f41..74997b26d 100644
--- a/src/print.rs
+++ b/src/print.rs
@@ -13,6 +13,7 @@ use crate::modules;
 // prompt heading of config docs needs to be updated according to changes made here.
 const DEFAULT_PROMPT_ORDER: &[&str] = &[
     "username",
+    "hostname",
     "directory",
     "git_branch",
     "git_status",
diff --git a/tests/testsuite/hostname.rs b/tests/testsuite/hostname.rs
new file mode 100644
index 000000000..8a1a7bbd9
--- /dev/null
+++ b/tests/testsuite/hostname.rs
@@ -0,0 +1,117 @@
+use ansi_term::{Color, Style};
+use std::io;
+
+use crate::common;
+use crate::common::TestCommand;
+
+#[test]
+fn ssh_only_false() -> io::Result<()> {
+    let hostname = match get_hostname() {
+        Some(h) => h,
+        None => return hostname_not_tested(),
+    };
+    let output = common::render_module("hostname")
+        .env_clear()
+        .use_config(toml::toml! {
+            [hostname]
+            ssh_only = false
+        })
+        .output()?;
+    let actual = String::from_utf8(output.stdout).unwrap();
+    let expected = format!("on {} ", style().paint(hostname));
+    assert_eq!(expected, actual);
+    Ok(())
+}
+
+#[test]
+fn no_ssh() -> io::Result<()> {
+    let output = common::render_module("hostname")
+        .env_clear()
+        .use_config(toml::toml! {
+            [hostname]
+            ssh_only = true
+        })
+        .output()?;
+    let actual = String::from_utf8(output.stdout).unwrap();
+    assert_eq!("", actual);
+    Ok(())
+}
+
+#[test]
+fn ssh() -> io::Result<()> {
+    let hostname = match get_hostname() {
+        Some(h) => h,
+        None => return hostname_not_tested(),
+    };
+    let output = common::render_module("hostname")
+        .env_clear()
+        .use_config(toml::toml! {
+            [hostname]
+            ssh_only = true
+        })
+        .env("SSH_CONNECTION", "something")
+        .output()?;
+    let actual = String::from_utf8(output.stdout).unwrap();
+    let expected = format!("on {} ", style().paint(hostname));
+    assert_eq!(expected, actual);
+    Ok(())
+}
+
+#[test]
+fn prefix() -> io::Result<()> {
+    let hostname = match get_hostname() {
+        Some(h) => h,
+        None => return hostname_not_tested(),
+    };
+    let output = common::render_module("hostname")
+        .env_clear()
+        .use_config(toml::toml! {
+            [hostname]
+            ssh_only = false
+            prefix = "<"
+        })
+        .output()?;
+    let actual = String::from_utf8(output.stdout).unwrap();
+    let expected = format!("on {} ", style().paint(format!("<{}", hostname)));
+    assert_eq!(actual, expected);
+    Ok(())
+}
+
+#[test]
+fn suffix() -> io::Result<()> {
+    let hostname = match get_hostname() {
+        Some(h) => h,
+        None => return hostname_not_tested(),
+    };
+    let output = common::render_module("hostname")
+        .env_clear()
+        .use_config(toml::toml! {
+            [hostname]
+            ssh_only = false
+            suffix = ">"
+        })
+        .output()?;
+    let actual = String::from_utf8(output.stdout).unwrap();
+    let expected = format!("on {} ", style().paint(format!("{}>", hostname)));
+    assert_eq!(actual, expected);
+    Ok(())
+}
+
+fn get_hostname() -> Option<String> {
+    match gethostname::gethostname().into_string() {
+        Ok(hostname) => Some(hostname),
+        Err(_) => None,
+    }
+}
+
+fn style() -> Style {
+    Color::Green.bold().dimmed()
+}
+
+fn hostname_not_tested() -> io::Result<()> {
+    println!(
+        "hostname was not tested because gethostname failed! \
+         This could be caused by your hostname containing invalid UTF."
+    );
+    Ok(())
+}
diff --git a/tests/testsuite/main.rs b/tests/testsuite/main.rs
index cd96b8e85..82da9cccf 100644
--- a/tests/testsuite/main.rs
+++ b/tests/testsuite/main.rs
@@ -6,6 +6,7 @@ mod directory;
 mod git_branch;
 mod git_status;
 mod golang;
+mod hostname;
 mod jobs;
 mod line_break;
 mod modules;