improve error handling

src/backend/rust.rs

@@ -21,14 +21,15 @@ impl Backend for Rust {
     impl_backend_constants!();
 
     fn get_all_installed_packages(&self) -> Result<HashSet<Package>> {
-        let file = get_crates_file().unwrap();
-        let content = read_to_string(file).unwrap();
-        let json: Value = serde_json::from_str(&content).unwrap();
-        extract_packages(json)
+        let file = get_crates_file().context("getting path to crates file")?;
+        let content = read_to_string(file).context("reading crates file")?;
+        let json: Value = serde_json::from_str(&content).context("parsing JSON")?;
+        extract_packages(json).context("extracing packages from JSON")
     }
 
     fn get_explicitly_installed_packages(&self) -> Result<HashSet<Package>> {
         self.get_all_installed_packages()
+            .context("getting all installed packages")
     }
 }
 

src/core.rs

@@ -4,8 +4,9 @@ use anyhow::{ensure, Context, Result};
 use clap::ArgMatches;
 
 use crate::action;
-use crate::backend::{Backends, ToDoPerBackend};
+use crate::backend::{Backend, Backends, ToDoPerBackend};
 use crate::cmd::run_edit_command;
+use crate::env::get_single_var;
 use crate::ui::get_user_confirmation;
 use crate::Group;
 
@@ -32,7 +33,9 @@ impl Pacdef {
             Some((action::UNMANAGED, _)) => Ok(self.show_unmanaged_packages()),
             Some((action::VERSION, _)) => Ok(self.show_version()),
             Some((_, _)) => todo!(),
-            None => unreachable!(),
+            None => {
+                unreachable!("argument parser requires some subcommand to return an `ArgMatches`")
+            }
         }
     }
 
@@ -44,7 +47,7 @@ impl Pacdef {
 
             match backend.get_missing_packages_sorted() {
                 Ok(diff) => to_install.push((backend, diff)),
-                Err(e) => println!("WARNING: skipping backend '{}': {e}", backend.get_section()),
+                Err(error) => show_error(error, backend),
             };
         }
 
@@ -123,7 +126,7 @@ impl Pacdef {
 
             match backend.get_unmanaged_packages_sorted() {
                 Ok(unmanaged) => result.push((backend, unmanaged)),
-                Err(e) => println!("WARNING: skipping backend '{}': {e}", backend.get_section()),
+                Err(error) => show_error(error, backend),
             };
         }
         result
@@ -165,3 +168,15 @@ impl Pacdef {
         }
     }
 }
+
+fn show_error(error: anyhow::Error, backend: Box<dyn Backend>) {
+    let section = backend.get_section();
+    match get_single_var("RUST_BACKTRACE") {
+        Some(s) => {
+            if s == "1" || s == "full" {
+                println!("WARNING: skipping backend '{section}': {error:?}\n");
+            }
+        }
+        None => println!("WARNING: skipping backend '{section}': {error}"),
+    }
+}

src/env.rs

@@ -9,3 +9,7 @@ pub(crate) fn get_editor() -> Result<String> {
 fn check_vars_in_order(vars: &[&str]) -> Option<String> {
     vars.iter().flat_map(|v| var(v).ok()).next()
 }
+
+pub(crate) fn get_single_var(variable: &str) -> Option<String> {
+    var(variable).ok()
+}