Allow expected errors (#116)

* Move binary out of /nix if it is there during uninstall

* Add tracing

* Sorta working...

* Have expected() return an err

* Better handle expected errors during install

* Hello trailing whitespace

src/action/mod.rs

@@ -160,6 +160,8 @@ pub use stateful::{ActionState, StatefulAction};
 use std::error::Error;
 use tokio::task::JoinError;
 
+use crate::error::HasExpectedErrors;
+
 /// An action which can be reverted or completed, with an action state
 ///
 /// This trait interacts with [`StatefulAction`] which does the [`ActionState`] manipulation and provides some tracing facilities.
@@ -308,3 +310,9 @@ pub enum ActionError {
         std::string::FromUtf8Error,
     ),
 }
+
+impl HasExpectedErrors for ActionError {
+    fn expected(&self) -> Option<Box<dyn std::error::Error>> {
+        None
+    }
+}

src/cli/subcommand/install.rs

@@ -6,6 +6,7 @@ use std::{
 use crate::{
     action::ActionState,
     cli::{ensure_root, interaction, signal_channel, CommandExecute},
+    error::HasExpectedErrors,
     plan::RECEIPT_LOCATION,
     planner::Planner,
     BuiltinPlanner, InstallPlan,
@@ -99,7 +100,17 @@ impl CommandExecute for Install {
                 let builtin_planner = BuiltinPlanner::default()
                     .await
                     .map_err(|e| eyre::eyre!(e))?;
-                builtin_planner.plan().await.map_err(|e| eyre!(e))?
+                let res = builtin_planner.plan().await;
+                match res {
+                    Ok(plan) => plan,
+                    Err(e) => {
+                        if let Some(expected) = e.expected() {
+                            eprintln!("{}", expected.red());
+                            return Ok(ExitCode::FAILURE);
+                        }
+                        return Err(e.into())
+                    }
+                }
             },
             (Some(_), Some(_)) => return Err(eyre!("`--plan` conflicts with passing a planner, a planner creates plans, so passing an existing plan doesn't make sense")),
         };
@@ -120,9 +131,17 @@ impl CommandExecute for Install {
         let (tx, rx1) = signal_channel().await?;
 
         if let Err(err) = install_plan.install(rx1).await {
-            let error = eyre!(err).wrap_err("Install failure");
             if !no_confirm {
+                let mut was_expected = false;
+                if let Some(expected) = err.expected() {
+                    was_expected = true;
+                    eprintln!("{}", expected.red())
+                }
+                if !was_expected {
+                    let error = eyre!(err).wrap_err("Install failure");
                     tracing::error!("{:?}", error);
+                };
+
                 if !interaction::confirm(
                     install_plan
                         .describe_uninstall(explain)
@@ -134,8 +153,22 @@ impl CommandExecute for Install {
                     interaction::clean_exit_with_message("Okay, didn't do anything! Bye!").await;
                 }
                 let rx2 = tx.subscribe();
-                install_plan.uninstall(rx2).await?
+                let res = install_plan.uninstall(rx2).await;
+
+                if let Err(e) = res {
+                    if let Some(expected) = e.expected() {
+                        eprintln!("{}", expected.red());
+                        return Ok(ExitCode::FAILURE);
+                    }
+                    return Err(e.into());
+                }
             } else {
+                if let Some(expected) = err.expected() {
+                    eprintln!("{}", expected.red());
+                    return Ok(ExitCode::FAILURE);
+                }
+
+                let error = eyre!(err).wrap_err("Install failure");
                 return Err(error);
             }
         }

src/cli/subcommand/plan.rs

@@ -1,9 +1,10 @@
 use std::{path::PathBuf, process::ExitCode};
 
-use crate::BuiltinPlanner;
+use crate::{error::HasExpectedErrors, BuiltinPlanner};
 use clap::Parser;
 
 use eyre::WrapErr;
+use owo_colors::OwoColorize;
 
 use crate::cli::CommandExecute;
 
@@ -29,7 +30,18 @@ impl CommandExecute for Plan {
                 .map_err(|e| eyre::eyre!(e))?,
         };
 
-        let install_plan = planner.plan().await.map_err(|e| eyre::eyre!(e))?;
+        let res = planner.plan().await;
+
+        let install_plan = match res {
+            Ok(plan) => plan,
+            Err(e) => {
+                if let Some(expected) = e.expected() {
+                    eprintln!("{}", expected.red());
+                    return Ok(ExitCode::FAILURE);
+                }
+                return Err(e.into());
+            },
+        };
 
         let json = serde_json::to_string_pretty(&install_plan)?;
         tokio::fs::write(output, json)

src/cli/subcommand/uninstall.rs

@@ -6,6 +6,7 @@ use std::{
 
 use crate::{
     cli::{ensure_root, signal_channel},
+    error::HasExpectedErrors,
     plan::RECEIPT_LOCATION,
     InstallPlan,
 };
@@ -93,6 +94,33 @@ impl CommandExecute for Uninstall {
             }
         }
 
+        // During install, `harmonic` will store a copy of itself in `/nix/harmonic`
+        // If the user opted to run that particular copy of Harmonic to do this uninstall,
+        // well, we have a problem, since the binary would delete itself.
+        // Instead, detect if we're in that location, if so, move the binary and `execv` it.
+        if let Ok(current_exe) = std::env::current_exe() {
+            if current_exe.as_path() == Path::new("/nix/harmonic") {
+                tracing::debug!(
+                    "Detected uninstall from `/nix/harmonic`, moving executable and re-executing"
+                );
+                let temp = std::env::temp_dir();
+                let temp_exe = temp.join("harmonic");
+                tokio::fs::copy(&current_exe, &temp_exe)
+                    .await
+                    .wrap_err("Copying harmonic to tempdir")?;
+                let args = std::env::args();
+                let mut arg_vec_cstring = vec![];
+                for arg in args {
+                    arg_vec_cstring.push(CString::new(arg).wrap_err("Making arg into C string")?);
+                }
+                let temp_exe_cstring = CString::new(temp_exe.to_string_lossy().into_owned())
+                    .wrap_err("Making C string of executable path")?;
+
+                nix::unistd::execv(&temp_exe_cstring, &arg_vec_cstring)
+                    .wrap_err("Executing copied Harmonic")?;
+            }
+        }
+
         let install_receipt_string = tokio::fs::read_to_string(receipt)
             .await
             .wrap_err("Reading receipt")?;
@@ -111,7 +139,15 @@ impl CommandExecute for Uninstall {
 
         let (_tx, rx) = signal_channel().await?;
 
-        plan.uninstall(rx).await?;
+        let res = plan.uninstall(rx).await;
+        if let Err(e) = res {
+            if let Some(expected) = e.expected() {
+                println!("{}", expected.red());
+                return Ok(ExitCode::FAILURE);
+            }
+            return Err(e.into());
+        }
+
         // TODO(@hoverbear): It would be so nice to catch errors and offer the user a way to keep going...
         //                   However that will require being able to link error -> step and manually setting that step as `Uncompleted`.
 

src/error.rs

@@ -54,3 +54,22 @@ pub enum HarmonicError {
         InstallSettingsError,
     ),
 }
+
+pub(crate) trait HasExpectedErrors {
+    fn expected<'a>(&'a self) -> Option<Box<dyn std::error::Error + 'a>>;
+}
+
+impl HasExpectedErrors for HarmonicError {
+    fn expected<'a>(&'a self) -> Option<Box<dyn std::error::Error + 'a>> {
+        match self {
+            HarmonicError::Action(action_error) => action_error.expected(),
+            HarmonicError::RecordingReceipt(_, _) => None,
+            HarmonicError::CopyingSelf(_) => None,
+            HarmonicError::SerializingReceipt(_) => None,
+            HarmonicError::Cancelled => None,
+            HarmonicError::SemVer(_) => None,
+            HarmonicError::Planner(planner_error) => planner_error.expected(),
+            HarmonicError::InstallSettings(_) => None,
+        }
+    }
+}

src/planner/linux/multi.rs

@@ -33,7 +33,7 @@ impl Planner for LinuxMulti {
         // If on NixOS, running `harmonic` is pointless
         // NixOS always sets up this file as part of setting up /etc itself: https://github.com/NixOS/nixpkgs/blob/bdd39e5757d858bd6ea58ed65b4a2e52c8ed11ca/nixos/modules/system/etc/setup-etc.pl#L145
         if Path::new("/etc/NIXOS").exists() {
-            return Err(PlannerError::Custom(Box::new(LinuxMultiError::NixOs)));
+            return Err(PlannerError::NixOs);
         }
 
         // For now, we don't try to repair the user's Nix install or anything special.
@@ -43,7 +43,7 @@ impl Planner for LinuxMulti {
             .status()
             .await
         {
-            return Err(PlannerError::Custom(Box::new(LinuxMultiError::NixExists)));
+            return Err(PlannerError::NixExists);
         }
 
         Ok(vec![
@@ -84,10 +84,6 @@ impl Into<BuiltinPlanner> for LinuxMulti {
 
 #[derive(thiserror::Error, Debug)]
 enum LinuxMultiError {
-    #[error("NixOS already has Nix installed")]
-    NixOs,
-    #[error("`nix` is already a valid command, so it is installed")]
-    NixExists,
     #[error("Error planning action")]
     Action(
         #[source]

src/planner/mod.rs

@@ -81,6 +81,7 @@ use std::collections::HashMap;
 
 use crate::{
     action::{ActionError, StatefulAction},
+    error::HasExpectedErrors,
     settings::InstallSettingsError,
     Action, HarmonicError, InstallPlan,
 };
@@ -181,4 +182,22 @@ pub enum PlannerError {
     /// Custom planner error
     #[error("Custom planner error")]
     Custom(#[source] Box<dyn std::error::Error + Send + Sync>),
+    #[error("NixOS already has Nix installed")]
+    NixOs,
+    #[error("`nix` is already a valid command, so it is installed")]
+    NixExists,
+}
+
+impl HasExpectedErrors for PlannerError {
+    fn expected<'a>(&'a self) -> Option<Box<dyn std::error::Error + 'a>> {
+        match self {
+            this @ PlannerError::UnsupportedArchitecture(_) => Some(Box::new(this)),
+            PlannerError::Action(_) => None,
+            PlannerError::InstallSettings(_) => None,
+            PlannerError::Plist(_) => None,
+            PlannerError::Custom(_) => None,
+            this @ PlannerError::NixOs => Some(Box::new(this)),
+            this @ PlannerError::NixExists => Some(Box::new(this)),
+        }
+    }
 }