feat: add hostname module (#286)

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

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(())
+}

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;