feat: add Haskell Stack support (#546)

Add a Haskell Stack module when a stack.yaml file is detected

tests/testsuite/haskell.rs

@@ -0,0 +1,71 @@
+use ansi_term::Color;
+use dirs::home_dir;
+use std::fs::{File, OpenOptions};
+use std::io::{self, Write};
+use tempfile::{self, TempDir};
+
+use crate::common;
+
+#[test]
+fn folder_without_stack_yaml() -> io::Result<()> {
+    let dir = tempfile::tempdir()?;
+
+    let output = common::render_module("haskell")
+        .arg("--path")
+        .arg(dir.path())
+        .output()?;
+    let actual = String::from_utf8(output.stdout).unwrap();
+
+    let expected = "";
+    assert_eq!(expected, actual);
+    Ok(())
+}
+
+#[test]
+#[ignore]
+#[cfg(not(windows))]
+fn folder_with_stack_yaml() -> io::Result<()> {
+    let dir = tempfile::tempdir()?;
+    create_dummy_haskell_project(&dir, Some("nightly-2019-09-21 # Last GHC 8.6.5"))?;
+
+    let output = if cfg!(windows) {
+        let mut app_data = home_dir().unwrap();
+        app_data.push("AppData");
+        app_data.push("Local");
+        eprintln!("{}", app_data.to_str().unwrap());
+        common::render_module("haskell")
+            .env("HOME", home_dir().unwrap())
+            .env("LOCALAPPDATA", app_data)
+            .env("STACK_ROOT", r"C:\sr")
+            .arg("--path")
+            .arg(dir.path())
+            .output()?
+    } else {
+        common::render_module("haskell")
+            .env("HOME", home_dir().unwrap())
+            .arg("--path")
+            .arg(dir.path())
+            .output()?
+    };
+
+    let actual = String::from_utf8(output.stdout).unwrap();
+
+    let expected = format!("via {} ", Color::Red.bold().paint("λ v8.6.5"));
+    assert_eq!(expected, actual);
+    Ok(())
+}
+
+fn create_dummy_haskell_project(folder: &TempDir, contents: Option<&str>) -> io::Result<()> {
+    let cabal_path = folder.path().join("test.cabal");
+    File::create(cabal_path)?.sync_all()?;
+
+    let stack_yaml_path = folder.path().join("stack.yaml");
+
+    let mut stack_yaml_file = OpenOptions::new()
+        .write(true)
+        .create(true)
+        .truncate(true)
+        .open(&stack_yaml_path)?;
+    write!(stack_yaml_file, "resolver: {}", contents.unwrap_or(""))?;
+    stack_yaml_file.sync_data()
+}

tests/testsuite/main.rs

@@ -12,6 +12,7 @@ mod git_commit;
 mod git_state;
 mod git_status;
 mod golang;
+mod haskell;
 mod hg_branch;
 mod hostname;
 mod jobs;