Introduce support for user-provided extensions

This change introduces support for discovering and executing
user-provided extensions to the program. Extensions are useful for
allowing users to provide additional functionality on top of the
nitrocli proper. Implementation wise we stick to an approach similar to
git or cargo subcommands in nature: we search the directories listed in
the PATH environment variable for a file that starts with "nitrocli-",
followed by the extension name. This file is then executed. It is
assumed that the extension recognizes (or at least not prohibits) the
following arguments: --nitrocli (providing the path to the nitrocli
binary), --model (with the model passed to the main program), and
--verbosity (the verbosity level).

1 files changed, 115 insertions, 0 deletions

diff --git a/src/tests/run.rs b/src/tests/run.rs
index 33191d3..e4bbb28 100644
--- a/src/tests/run.rs
+++ b/src/tests/run.rs
@@ -5,8 +5,12 @@
 
 use std::collections;
 use std::convert;
+use std::convert::TryFrom as _;
 use std::convert::TryInto as _;
+use std::fs;
+use std::io::Write;
 use std::ops;
+use std::os::unix::fs::OpenOptionsExt;
 use std::path;
 
 use super::*;
@@ -277,3 +281,114 @@ fn connect_usb_path_model_wrong_serial(_model: nitrokey::Model) -> anyhow::Resul
   }
   Ok(())
 }
+
+#[test]
+fn extension() -> anyhow::Result<()> {
+  let ext_dir = tempfile::tempdir()?;
+  {
+    let mut ext = fs::OpenOptions::new()
+      .create(true)
+      .mode(0o755)
+      .write(true)
+      .open(ext_dir.path().join("nitrocli-ext"))?;
+
+    ext.write_all(
+      br#"#!/usr/bin/env python
+print("success")
+"#,
+    )?;
+  }
+
+  let path = ext_dir.path().as_os_str().to_os_string();
+  let out = Nitrocli::new().path(path).handle(&["ext"])?;
+  assert_eq!(out, "success\n");
+  Ok(())
+}
+
+#[test]
+fn extension_failure() -> anyhow::Result<()> {
+  let ext_dir = tempfile::tempdir()?;
+  {
+    let mut ext = fs::OpenOptions::new()
+      .create(true)
+      .mode(0o755)
+      .write(true)
+      .open(ext_dir.path().join("nitrocli-ext"))?;
+
+    ext.write_all(
+      br#"#!/usr/bin/env python
+import sys
+sys.exit(42);
+"#,
+    )?;
+  }
+
+  let path = ext_dir.path().as_os_str().to_os_string();
+  let mut ncli = Nitrocli::new().path(path);
+
+  let err = ncli.handle(&["ext"]).unwrap_err();
+  // The extension is responsible for printing any error messages.
+  // Nitrocli is expected not to mess with them, including adding
+  // additional information.
+  if let Some(crate::DirectExitError(rc)) = err.downcast_ref::<crate::DirectExitError>() {
+    assert_eq!(*rc, 42)
+  } else {
+    panic!("encountered unexpected error: {:#}", err)
+  }
+
+  let (rc, out, err) = ncli.run(&["ext"]);
+  assert_eq!(rc, 42);
+  assert_eq!(out, b"");
+  assert_eq!(err, b"");
+  Ok(())
+}
+
+#[test_device]
+fn extension_arguments(model: nitrokey::Model) -> anyhow::Result<()> {
+  fn test<F>(model: nitrokey::Model, what: &str, args: &[&str], check: F) -> anyhow::Result<()>
+  where
+    F: FnOnce(&str) -> bool,
+  {
+    let ext_dir = tempfile::tempdir()?;
+    {
+      let mut ext = fs::OpenOptions::new()
+        .create(true)
+        .mode(0o755)
+        .write(true)
+        .open(ext_dir.path().join("nitrocli-ext"))?;
+
+      ext.write_all(include_bytes!("extension_var_test.py"))?;
+    }
+
+    let mut args = args.to_vec();
+    args.append(&mut vec!["ext", what]);
+
+    let path = ext_dir.path().as_os_str().to_os_string();
+    let out = Nitrocli::new().model(model).path(path).handle(&args)?;
+
+    assert!(check(&out), out);
+    Ok(())
+  }
+
+  test(model, "binary", &[], |out| {
+    path::Path::new(out)
+      .file_stem()
+      .unwrap()
+      .to_str()
+      .unwrap()
+      .trim()
+      .contains("nitrocli")
+  })?;
+  test(model, "model", &[], |out| {
+    out == args::DeviceModel::try_from(model).unwrap().to_string() + "\n"
+  })?;
+  test(model, "no-cache", &[], |out| out == "true\n")?;
+  test(model, "serial-numbers", &[], |out| out == "\n")?;
+  test(model, "verbosity", &[], |out| out == "0\n")?;
+  test(model, "verbosity", &["-v"], |out| out == "1\n")?;
+  test(model, "verbosity", &["-v", "--verbose"], |out| out == "2\n")?;
+
+  // NITROCLI_USB_PATH should not be set, so the program errors out.
+  let _ = test(model, "usb-path", &[], |out| out == "\n").unwrap_err();
+  Ok(())
+}