feat: Add Java Module (#314)

Implements a Java module which shows basic Java information when inside a Java project.

src/module.rs

@@ -16,6 +16,7 @@ pub const ALL_MODULES: &[&str] = &[
     "git_status",
     "golang",
     "hostname",
+    "java",
     "jobs",
     "line_break",
     "nix_shell",

src/modules/java.rs

@@ -0,0 +1,105 @@
+use std::process::Command;
+
+use ansi_term::Color;
+
+use super::{Context, Module};
+
+/// Creates a module with the current Java version
+///
+/// Will display the Java version if any of the following criteria are met:
+///     - Current directory contains a file with a `.java`, `.class` or `.jar` extension
+///     - Current directory contains a `pom.xml` or `build.gradle` file
+pub fn module<'a>(context: &'a Context) -> Option<Module<'a>> {
+    let is_java_project = context
+        .try_begin_scan()?
+        .set_files(&["pom.xml", "build.gradle"])
+        .set_extensions(&["java", "class", "jar"])
+        .is_match();
+
+    if !is_java_project {
+        return None;
+    }
+
+    match get_java_version() {
+        Some(java_version) => {
+            const JAVA_CHAR: &str = "☕ ";
+
+            let mut module = context.new_module("java");
+            let module_style = module
+                .config_value_style("style")
+                .unwrap_or_else(|| Color::Red.dimmed());
+            module.set_style(module_style);
+
+            let formatted_version = format_java_version(java_version)?;
+            module.new_segment("symbol", JAVA_CHAR);
+            module.new_segment("version", &formatted_version);
+
+            Some(module)
+        }
+        None => None,
+    }
+}
+
+fn get_java_version() -> Option<String> {
+    let java_command = match std::env::var("JAVA_HOME") {
+        Ok(java_home) => format!("{}/bin/java", java_home),
+        Err(_) => String::from("java"),
+    };
+
+    match Command::new(java_command).arg("-Xinternalversion").output() {
+        Ok(output) => Some(String::from_utf8(output.stdout).unwrap()),
+        Err(_) => None,
+    }
+}
+
+/// Extract the java version from `java_stdout`.
+/// The expected format is similar to: "JRE (1.8.0_222-b10)".
+/// Some Java vendors don't follow this format: "JRE (Zulu 8.40.0.25-CA-linux64)").
+fn format_java_version(java_stdout: String) -> Option<String> {
+    let start = java_stdout.find("JRE (")? + "JRE (".len();
+    let end = start
+        + (java_stdout[start..].find(|c| match c {
+            '0'..='9' | '.' => false,
+            _ => true,
+        })?);
+
+    if start == end {
+        None
+    } else {
+        Some(format!("v{}", &java_stdout[start..end]))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_format_java_version_openjdk() {
+        let java_8 = String::from("OpenJDK 64-Bit Server VM (25.222-b10) for linux-amd64 JRE (1.8.0_222-b10), built on Jul 11 2019 10:18:43 by \"openjdk\" with gcc 4.4.7 20120313 (Red Hat 4.4.7-23)");
+        let java_11 = String::from("OpenJDK 64-Bit Server VM (11.0.4+11-post-Ubuntu-1ubuntu219.04) for linux-amd64 JRE (11.0.4+11-post-Ubuntu-1ubuntu219.04), built on Jul 18 2019 18:21:46 by \"build\" with gcc 8.3.0");
+        assert_eq!(format_java_version(java_11), Some(String::from("v11.0.4")));
+        assert_eq!(format_java_version(java_8), Some(String::from("v1.8.0")));
+    }
+
+    #[test]
+    fn test_format_java_version_oracle() {
+        let java_8 = String::from("Java HotSpot(TM) Client VM (25.65-b01) for linux-arm-vfp-hflt JRE (1.8.0_65-b17), built on Oct  6 2015 16:19:04 by \"java_re\" with gcc 4.7.2 20120910 (prerelease)");
+        assert_eq!(format_java_version(java_8), Some(String::from("v1.8.0")));
+    }
+
+    #[test]
+    fn test_format_java_version_redhat() {
+        let java_8 = String::from("OpenJDK 64-Bit Server VM (25.222-b10) for linux-amd64 JRE (1.8.0_222-b10), built on Jul 11 2019 20:48:53 by \"root\" with gcc 7.3.1 20180303 (Red Hat 7.3.1-5)");
+        let java_12 = String::from("OpenJDK 64-Bit Server VM (12.0.2+10) for linux-amd64 JRE (12.0.2+10), built on Jul 18 2019 14:41:47 by \"jenkins\" with gcc 7.3.1 20180303 (Red Hat 7.3.1-5)");
+        assert_eq!(format_java_version(java_8), Some(String::from("v1.8.0")));
+        assert_eq!(format_java_version(java_12), Some(String::from("v12.0.2")));
+    }
+
+    #[test]
+    fn test_format_java_version_zulu() {
+        // Not currently supported
+        let java_8 = String::from("OpenJDK 64-Bit Server VM (25.222-b10) for linux-amd64 JRE (Zulu 8.40.0.25-CA-linux64) (1.8.0_222-b10), built on Jul 11 2019 11:36:39 by \"zulu_re\" with gcc 4.4.7 20120313 (Red Hat 4.4.7-3)");
+        assert_eq!(format_java_version(java_8), None);
+    }
+}

src/modules/mod.rs

@@ -7,6 +7,7 @@ mod git_state;
 mod git_status;
 mod golang;
 mod hostname;
+mod java;
 mod jobs;
 mod line_break;
 mod nix_shell;
@@ -42,6 +43,7 @@ pub fn handle<'a>(module: &str, context: &'a Context) -> Option<Module<'a>> {
         #[cfg(feature = "battery")]
         "battery" => battery::module(context),
         "cmd_duration" => cmd_duration::module(context),
+        "java" => java::module(context),
         "jobs" => jobs::module(context),
         "nix_shell" => nix_shell::module(context),
         "hostname" => hostname::module(context),

src/print.rs

@@ -24,6 +24,7 @@ const DEFAULT_PROMPT_ORDER: &[&str] = &[
     "rust",
     "python",
     "golang",
+    "java",
     "nix_shell",
     "cmd_duration",
     "line_break",