Install can detect existing /nix/receipt.json

src/cli/subcommand/install.rs

@@ -1,6 +1,9 @@
-use std::{path::PathBuf, process::ExitCode};
+use std::{
+    path::{Path, PathBuf},
+    process::ExitCode,
+};
 
-use crate::BuiltinPlanner;
+use crate::{plan::RECEIPT_LOCATION, BuiltinPlanner, InstallPlan, Planner};
 use clap::{ArgAction, Parser};
 use eyre::{eyre, WrapErr};
 
@@ -8,7 +11,7 @@ use crate::{cli::CommandExecute, interaction};
 
 /// Execute an install (possibly using an existing plan)
 #[derive(Debug, Parser)]
-#[command(args_conflicts_with_subcommands = true)]
+#[command(args_conflicts_with_subcommands = true, arg_required_else_help = true)]
 pub struct Install {
     #[clap(
         long,
@@ -29,7 +32,7 @@ pub struct Install {
     pub plan: Option<PathBuf>,
 
     #[clap(subcommand)]
-    pub planner: BuiltinPlanner,
+    pub planner: Option<BuiltinPlanner>,
 }
 
 #[async_trait::async_trait]
@@ -43,28 +46,61 @@ impl CommandExecute for Install {
             explain,
         } = self;
 
-        let mut plan = match &plan {
-            Some(plan_path) => {
-                let install_plan_string = tokio::fs::read_to_string(&plan_path)
+        let existing_receipt: Option<InstallPlan> = match Path::new(RECEIPT_LOCATION).exists() {
+            true => {
+                let install_plan_string = tokio::fs::read_to_string(&RECEIPT_LOCATION)
                     .await
                     .wrap_err("Reading plan")?;
+                Some(serde_json::from_str(&install_plan_string)?)
+            },
+            false => None,
+        };
+
+        let mut install_plan = match (planner, plan) {
+            (Some(planner), None) => {
+                let chosen_planner: Box<dyn Planner> = planner.clone().boxed();
+
+                match existing_receipt {
+                    Some(existing_receipt) => {
+                        if existing_receipt.planner.typetag_name() == chosen_planner.typetag_name() {
+                            existing_receipt
+                        } else {
+                            return Err(eyre!("Found existing plan in `/nix/receipt.json` which used a different planner, try uninstalling the existing install"))
+                        }
+                    } ,
+                    None => {
+                        planner.plan().await.map_err(|e| eyre!(e))?
+                    },
+                }
+            },
+            (None, Some(plan_path)) => {
+                let install_plan_string = tokio::fs::read_to_string(&plan_path)
+                .await
+                .wrap_err("Reading plan")?;
                 serde_json::from_str(&install_plan_string)?
             },
-            None => planner.plan().await.map_err(|e| eyre!(e))?,
+            (None, None) => return Err(eyre!("`--plan` or a planner is required")),
+            (Some(_), Some(_)) => return Err(eyre!("`--plan` conflicts with passing a planner, a planner creates plans, so passing an existing plan doesn't make sense")),
         };
 
         if !no_confirm {
-            if !interaction::confirm(plan.describe_execute(explain).map_err(|e| eyre!(e))?).await? {
+            if !interaction::confirm(
+                install_plan
+                    .describe_execute(explain)
+                    .map_err(|e| eyre!(e))?,
+            )
+            .await?
+            {
                 interaction::clean_exit_with_message("Okay, didn't do anything! Bye!").await;
             }
         }
 
-        if let Err(err) = plan.install().await {
+        if let Err(err) = install_plan.install().await {
             tracing::error!("{:?}", eyre!(err));
-            if !interaction::confirm(plan.describe_revert(explain)).await? {
+            if !interaction::confirm(install_plan.describe_revert(explain)).await? {
                 interaction::clean_exit_with_message("Okay, didn't do anything! Bye!").await;
             }
-            plan.revert().await?
+            install_plan.revert().await?
         }
 
         Ok(ExitCode::SUCCESS)

src/cli/subcommand/uninstall.rs

@@ -1,6 +1,6 @@
 use std::{path::PathBuf, process::ExitCode};
 
-use crate::InstallPlan;
+use crate::{plan::RECEIPT_LOCATION, InstallPlan};
 use clap::{ArgAction, Parser};
 use eyre::WrapErr;
 
@@ -23,7 +23,7 @@ pub struct Uninstall {
         global = true
     )]
     pub explain: bool,
-    #[clap(default_value = "/nix/receipt.json")]
+    #[clap(default_value = RECEIPT_LOCATION)]
     pub receipt: PathBuf,
 }
 

src/plan.rs

@@ -8,6 +8,8 @@ use crate::{
     HarmonicError,
 };
 
+pub const RECEIPT_LOCATION: &str = "/nix/receipt.json";
+
 #[derive(Debug, serde::Deserialize, serde::Serialize, Clone)]
 pub struct InstallPlan {
     pub(crate) actions: Vec<Box<dyn Action>>,
@@ -166,7 +168,7 @@ async fn write_receipt(plan: InstallPlan) -> Result<(), HarmonicError> {
     tokio::fs::create_dir_all("/nix")
         .await
         .map_err(|e| HarmonicError::RecordingReceipt(PathBuf::from("/nix"), e))?;
-    let install_receipt_path = PathBuf::from("/nix/receipt.json");
+    let install_receipt_path = PathBuf::from(RECEIPT_LOCATION);
     let self_json =
         serde_json::to_string_pretty(&plan).map_err(HarmonicError::SerializingReceipt)?;
     tokio::fs::write(&install_receipt_path, self_json)

src/planner/mod.rs

@@ -16,6 +16,12 @@ pub trait Planner: std::fmt::Debug + Send + Sync + dyn_clone::DynClone {
     fn describe(
         &self,
     ) -> Result<HashMap<String, serde_json::Value>, Box<dyn std::error::Error + Sync + Send>>;
+    fn boxed(self) -> Box<dyn Planner>
+    where
+        Self: Sized + 'static,
+    {
+        Box::new(self)
+    }
 }
 
 dyn_clone::clone_trait_object!(Planner);
@@ -56,6 +62,13 @@ impl BuiltinPlanner {
             BuiltinPlanner::SteamDeck(planner) => planner.plan().await,
         }
     }
+    pub fn boxed(self) -> Box<dyn Planner> {
+        match self {
+            BuiltinPlanner::LinuxMulti(i) => i.boxed(),
+            BuiltinPlanner::DarwinMulti(i) => i.boxed(),
+            BuiltinPlanner::SteamDeck(i) => i.boxed(),
+        }
+    }
 }
 
 #[derive(thiserror::Error, Debug)]