Better error message for bad filename CLI argument.

src/errors.rs

@@ -180,6 +180,7 @@ pub fn permission_denied() -> DenoError {
   )
 }
 
+#[derive(Debug)]
 pub enum RustOrJsError {
   Rust(DenoError),
   Js(JSError),
@@ -196,3 +197,12 @@ impl From<JSError> for RustOrJsError {
     RustOrJsError::Js(e)
   }
 }
+
+impl fmt::Display for RustOrJsError {
+  fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+    match self {
+      RustOrJsError::Rust(e) => e.fmt(f),
+      RustOrJsError::Js(e) => e.fmt(f),
+    }
+  }
+}

src/isolate.rs

@@ -404,17 +404,19 @@ impl Isolate {
     &mut self,
     js_filename: &str,
     is_prefetch: bool,
-  ) -> Result<(), JSError> {
-    let out =
-      code_fetch_and_maybe_compile(&self.state, js_filename, ".").unwrap();
+  ) -> Result<(), RustOrJsError> {
+    let out = code_fetch_and_maybe_compile(&self.state, js_filename, ".")
+      .map_err(RustOrJsError::from)?;
 
-    let id = self.mod_new(out.filename.clone(), out.js_source())?;
+    let id = self
+      .mod_new(out.filename.clone(), out.js_source())
+      .map_err(RustOrJsError::from)?;
 
-    self.mod_load_deps(id).ok();
+    self.mod_load_deps(id)?;
 
-    self.mod_instantiate(id)?;
+    self.mod_instantiate(id).map_err(RustOrJsError::from)?;
     if !is_prefetch {
-      self.mod_evaluate(id)?;
+      self.mod_evaluate(id).map_err(RustOrJsError::from)?;
     }
     Ok(())
   }

src/js_errors.rs

@@ -14,6 +14,7 @@ use source_map_mappings::parse_mappings;
 use source_map_mappings::Bias;
 use source_map_mappings::Mappings;
 use std::collections::HashMap;
+use std::fmt;
 
 pub trait SourceMapGetter {
   /// Returns the raw source map file.
@@ -73,39 +74,34 @@ impl ToString for StackFrame {
   }
 }
 
-impl ToString for JSError {
-  fn to_string(&self) -> String {
-    // TODO Improve the formatting of these error messages.
-    let mut s = String::new();
-
+impl fmt::Display for JSError {
+  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
     if self.script_resource_name.is_some() {
       let script_resource_name = self.script_resource_name.as_ref().unwrap();
       // Avoid showing internal code from gen/bundle/main.js
       if script_resource_name != "gen/bundle/main.js" {
-        s.push_str(script_resource_name);
+        write!(f, "{}", script_resource_name)?;
         if self.line_number.is_some() {
-          s.push_str(&format!(
+          write!(
+            f,
             ":{}:{}",
             self.line_number.unwrap(),
             self.start_column.unwrap()
-          ));
+          )?;
           assert!(self.start_column.is_some());
         }
         if self.source_line.is_some() {
-          s.push_str("\n");
-          s.push_str(self.source_line.as_ref().unwrap());
-          s.push_str("\n\n");
+          write!(f, "\n{}\n\n", self.source_line.as_ref().unwrap())?;
         }
       }
     }
 
-    s.push_str(&self.message);
+    write!(f, "{}", &self.message)?;
 
     for frame in &self.frames {
-      s.push_str("\n");
-      s.push_str(&frame.to_string());
+      write!(f, "\n{}", &frame.to_string())?;
     }
-    s
+    Ok(())
   }
 }
 

src/main.rs

@@ -55,7 +55,7 @@ impl log::Log for Logger {
   fn flush(&self) {}
 }
 
-fn print_err_and_exit(err: js_errors::JSError) {
+fn print_err_and_exit(err: errors::RustOrJsError) {
   eprintln!("{}", err.to_string());
   std::process::exit(1);
 }
@@ -100,6 +100,7 @@ fn main() {
     // Setup runtime.
     isolate
       .execute("denoMain();")
+      .map_err(errors::RustOrJsError::from)
       .unwrap_or_else(print_err_and_exit);
 
     // Execute input file.
@@ -110,6 +111,9 @@ fn main() {
         .unwrap_or_else(print_err_and_exit);
     }
 
-    isolate.event_loop().unwrap_or_else(print_err_and_exit);
+    isolate
+      .event_loop()
+      .map_err(errors::RustOrJsError::from)
+      .unwrap_or_else(print_err_and_exit);
   });
 }

tests/error_009_missing_js_module.js.out

@@ -1 +1 @@
-Uncaught Cannot resolve module "./bad-module.js" from "[WILDCARD]error_009_missing_js_module.js"
+Cannot resolve module "./bad-module.js" from "[WILDCARD]error_009_missing_js_module.js"

tests/error_010_nonexistent_arg.out

@@ -0,0 +1 @@
+[WILDCARD]Cannot resolve module "not-a-valid-filename.ts" from "."

tests/error_010_nonexistent_arg.test

@@ -0,0 +1,4 @@
+args: not-a-valid-filename.ts
+output: tests/error_010_nonexistent_arg.out
+exit_code: 1
+check_stderr: true