feat: replace panics with user-friendly errors

Closes #4

Author: jtdowney

src/main.rs

@@ -20,6 +20,17 @@ OPTIONS:
     -h, --help Show this help message
 ";
 
+fn report_template_error(err: minijinja::Error) -> ! {
+    eprint!("error: {err}");
+    let debug_info = err.display_debug_info();
+    let debug_info = debug_info.to_string();
+    if !debug_info.is_empty() {
+        eprint!("\n\n{debug_info}");
+    }
+    eprintln!();
+    process::exit(1);
+}
+
 fn main() {
     let mut args = pico_args::Arguments::from_env();
 
@@ -33,8 +44,11 @@ fn main() {
         .opt_free_from_str::<String>()
         .expect("Failed to parse arguments");
 
-    let template = if let Some(path) = template_path {
-        fs::read_to_string(&path).expect("Failed to read template file")
+    let template = if let Some(ref path) = template_path {
+        fs::read_to_string(path).unwrap_or_else(|err| {
+            eprintln!("error: {err} (path: {path})");
+            process::exit(1);
+        })
     } else {
         let mut input = String::new();
         io::stdin()
@@ -44,18 +58,23 @@ fn main() {
     };
 
     let mut env = Environment::new();
+    env.set_debug(true);
     if strict {
         env.set_undefined_behavior(UndefinedBehavior::Strict);
     }
 
-    env.add_template("template", &template)
-        .expect("Failed to add template");
+    if let Err(err) = env.add_template("template", &template) {
+        report_template_error(err);
+    }
 
     let tmpl = env
         .get_template("template")
         .expect("Failed to get template");
     let ctx = env::vars().collect::<HashMap<_, _>>();
 
-    let output = tmpl.render(&ctx).expect("Failed to render template");
+    let output = match tmpl.render(&ctx) {
+        Ok(output) => output,
+        Err(err) => report_template_error(err),
+    };
     println!("{output}");
 }

tests/integration_test.rs

@@ -7,13 +7,6 @@ fn cargo_run() -> Command {
     Command::new(env!("CARGO_BIN_EXE_rsubst"))
 }
 
-fn stderr_filters() -> Vec<(&'static str, &'static str)> {
-    vec![
-        (r"thread '.*' \(\d+\)", "[thread]"),
-        (r"src/main\.rs:\d+:\d+", "[file]"),
-    ]
-}
-
 #[test]
 fn test_simple_output() {
     let dir = tempdir().unwrap();
@@ -80,11 +73,7 @@ fn test_missing_template_file() {
 
     assert!(!output.status.success());
     let stderr = String::from_utf8(output.stderr).unwrap();
-    insta::with_settings!({
-        filters => stderr_filters()
-    }, {
-        insta::assert_snapshot!(stderr);
-    });
+    insta::assert_snapshot!(stderr);
 }
 
 #[test]
@@ -116,11 +105,7 @@ fn test_strict_errors_on_missing_variable() {
 
     assert!(!output.status.success());
     let stderr = String::from_utf8(output.stderr).unwrap();
-    insta::with_settings!({
-        filters => stderr_filters()
-    }, {
-        insta::assert_snapshot!(stderr);
-    });
+    insta::assert_snapshot!(stderr);
 }
 
 #[test]

tests/snapshots/integration_test__missing_template_file.snap

@@ -2,7 +2,4 @@
 source: tests/integration_test.rs
 expression: stderr
 ---
-
-[thread] panicked at [file]:
-Failed to read template file: Os { code: 2, kind: NotFound, message: "No such file or directory" }
-note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+error: No such file or directory (os error 2) (path: nonexistent.j2)

tests/snapshots/integration_test__strict_errors_on_missing_variable.snap

@@ -2,15 +2,12 @@
 source: tests/integration_test.rs
 expression: stderr
 ---
+error: undefined value (in template:1)
 
-[thread] panicked at [file]:
-Failed to render template: Error { kind: UndefinedError, name: "template", line: 1 }
 
 ---------------------------------- template -----------------------------------
    1 > Hello {{NAME}}!
      i         ^^^^ undefined value
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 No referenced variables
 -------------------------------------------------------------------------------
-
-note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace