refactor: reduce UnlockPolicy boilerplate

Signed-off-by: Thomas Mühlbacher <tmuehlbacher@posteo.net>

Cargo.lock

@@ -86,6 +86,8 @@ dependencies = [
  "libc",
  "log",
  "rpassword",
+ "strum",
+ "strum_macros",
  "udev",
  "uuid",
 ]
@@ -516,6 +518,12 @@ dependencies = [
  "windows-sys 0.52.0",
 ]
 
+[[package]]
+name = "rustversion"
+version = "1.0.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "955d28af4278de8121b7ebeb796b6a45735dc01436d898801014aced2773a3d6"
+
 [[package]]
 name = "shlex"
 version = "1.3.0"
@@ -528,6 +536,28 @@ version = "0.10.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "73473c0e59e6d5812c5dfe2a064a6444949f089e20eec9a2e5506596494e4623"
 
+[[package]]
+name = "strum"
+version = "0.26.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5d8cec3501a5194c432b2b7976db6b7d10ec95c253208b45f83f7136aa985e29"
+dependencies = [
+ "strum_macros",
+]
+
+[[package]]
+name = "strum_macros"
+version = "0.26.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c6cf59daf282c0a494ba14fd21610a0325f9f90ec9d1231dea26bcb1d696c946"
+dependencies = [
+ "heck",
+ "proc-macro2",
+ "quote",
+ "rustversion",
+ "syn",
+]
+
 [[package]]
 name = "syn"
 version = "2.0.48"

Cargo.toml

@@ -23,3 +23,5 @@ either = "1.5"
 rpassword = "7"
 bch_bindgen = { path = "bch_bindgen" }
 byteorder = "1.3"
+strum = { version = "0.26", features = ["derive"] }
+strum_macros = "0.26"

src/commands/mount.rs

@@ -231,7 +231,8 @@ pub struct Cli {
     #[arg(
         short = 'k',
         long = "key_location",
-        default_value = "ask",
+        value_enum,
+        default_value_t,
         verbatim_doc_comment
     )]
     unlock_policy: UnlockPolicy,

src/key.rs

@@ -1,63 +1,25 @@
 use std::{
-    fmt, fs,
+    fmt::Debug,
+    fs,
     io::{stdin, IsTerminal},
 };
 
-use crate::c_str;
 use anyhow::anyhow;
 use bch_bindgen::bcachefs::bch_sb_handle;
-use clap::builder::PossibleValue;
 use log::info;
 
-#[derive(Clone, Debug)]
+use crate::c_str;
+
+#[derive(Clone, Debug, clap::ValueEnum, strum::Display)]
 pub enum UnlockPolicy {
-    None,
     Fail,
     Wait,
     Ask,
 }
 
-impl std::str::FromStr for UnlockPolicy {
+impl Default for UnlockPolicy {
-    type Err = anyhow::Error;
+    fn default() -> Self {
-    fn from_str(s: &str) -> anyhow::Result<Self> {
+        Self::Ask
-        match s {
-            "" | "none" => Ok(UnlockPolicy::None),
-            "fail" => Ok(UnlockPolicy::Fail),
-            "wait" => Ok(UnlockPolicy::Wait),
-            "ask" => Ok(UnlockPolicy::Ask),
-            _ => Err(anyhow!("Invalid unlock policy provided")),
-        }
-    }
-}
-
-impl clap::ValueEnum for UnlockPolicy {
-    fn value_variants<'a>() -> &'a [Self] {
-        &[
-            UnlockPolicy::None,
-            UnlockPolicy::Fail,
-            UnlockPolicy::Wait,
-            UnlockPolicy::Ask,
-        ]
-    }
-
-    fn to_possible_value(&self) -> Option<PossibleValue> {
-        Some(match self {
-            Self::None => PossibleValue::new("none").alias(""),
-            Self::Fail => PossibleValue::new("fail"),
-            Self::Wait => PossibleValue::new("wait"),
-            Self::Ask => PossibleValue::new("ask"),
-        })
-    }
-}
-
-impl fmt::Display for UnlockPolicy {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match self {
-            UnlockPolicy::None => write!(f, "None"),
-            UnlockPolicy::Fail => write!(f, "Fail"),
-            UnlockPolicy::Wait => write!(f, "Wait"),
-            UnlockPolicy::Ask => write!(f, "Ask"),
-        }
     }
 }
 
@@ -185,6 +147,5 @@ pub fn apply_key_unlocking_policy(
         UnlockPolicy::Fail => Err(anyhow!("no passphrase available")),
         UnlockPolicy::Wait => Ok(wait_for_unlock(&block_device.sb().uuid())?),
         UnlockPolicy::Ask => ask_for_passphrase(block_device),
-        _ => Err(anyhow!("no unlock policy specified for locked filesystem")),
     }
 }