From c9571d375ad3c3a1fca017397e6ccc3b4c305532 Mon Sep 17 00:00:00 2001
From: Stephen Chung <Stephen.Chung@intexact.com>
Date: Wed, 6 May 2020 00:09:04 +0800
Subject: [PATCH] Add position to script error.

---
 README.md     |  7 +++++++
 src/api.rs    | 18 ++++++++++++++----
 src/engine.rs |  5 ++++-
 src/result.rs | 14 +++++++++-----
 4 files changed, 34 insertions(+), 10 deletions(-)

diff --git a/README.md b/README.md
index 5de326f1..d8c70be3 100644
--- a/README.md
+++ b/README.md
@@ -2120,6 +2120,13 @@ Built-in module resolvers are grouped under the `rhai::module_resolvers` module
 | `StaticModuleResolver` | Loads modules that are statically added. This can be used when the [`no_std`] feature is turned on.                                                                                                                                                                        |
 | `NullModuleResolver`   | The default module resolution service under the [`no_std`] feature. Always returns an `EvalAltResult::ErrorModuleNotFound` error.                                                                                                                                          |
 
+An [`Engine`]'s module resolver is set via a call to `set_module_resolver`:
+
+```rust
+// Use the 'NullModuleResolver'
+engine.set_module_resolver(rhai::module_resolvers::NullModuleResolver::new());
+```
+
 Script optimization
 ===================
 
diff --git a/src/api.rs b/src/api.rs
index 13c3a399..abc4d37f 100644
--- a/src/api.rs
+++ b/src/api.rs
@@ -437,13 +437,23 @@ impl Engine {
     /// Read the contents of a file into a string.
     #[cfg(not(feature = "no_std"))]
     fn read_file(path: PathBuf) -> Result<String, Box<EvalAltResult>> {
-        let mut f = File::open(path.clone())
-            .map_err(|err| Box::new(EvalAltResult::ErrorReadingScriptFile(path.clone(), err)))?;
+        let mut f = File::open(path.clone()).map_err(|err| {
+            Box::new(EvalAltResult::ErrorReadingScriptFile(
+                path.clone(),
+                Position::none(),
+                err,
+            ))
+        })?;
 
         let mut contents = String::new();
 
-        f.read_to_string(&mut contents)
-            .map_err(|err| Box::new(EvalAltResult::ErrorReadingScriptFile(path.clone(), err)))?;
+        f.read_to_string(&mut contents).map_err(|err| {
+            Box::new(EvalAltResult::ErrorReadingScriptFile(
+                path.clone(),
+                Position::none(),
+                err,
+            ))
+        })?;
 
         Ok(contents)
     }
diff --git a/src/engine.rs b/src/engine.rs
index c68efd95..a7beada9 100644
--- a/src/engine.rs
+++ b/src/engine.rs
@@ -1530,7 +1530,10 @@ impl Engine {
                     .eval_expr(scope, state, fn_lib, expr, level)?
                     .try_cast::<String>()
                 {
-                    let module = self.module_resolver.resolve(self, &path)?;
+                    let module = self
+                        .module_resolver
+                        .resolve(self, &path)
+                        .map_err(|err| EvalAltResult::set_position(err, expr.position()))?;
 
                     // TODO - avoid copying module name in inner block?
                     let mod_name = name.as_ref().clone();
diff --git a/src/result.rs b/src/result.rs
index 93846eb0..5e38f8d9 100644
--- a/src/result.rs
+++ b/src/result.rs
@@ -29,7 +29,7 @@ pub enum EvalAltResult {
     ///
     /// Never appears under the `no_std` feature.
     #[cfg(not(feature = "no_std"))]
-    ErrorReadingScriptFile(PathBuf, std::io::Error),
+    ErrorReadingScriptFile(PathBuf, Position, std::io::Error),
 
     /// Call to an unknown function. Wrapped value is the name of the function.
     ErrorFunctionNotFound(String, Position),
@@ -94,7 +94,7 @@ impl EvalAltResult {
     pub(crate) fn desc(&self) -> &str {
         match self {
             #[cfg(not(feature = "no_std"))]
-            Self::ErrorReadingScriptFile(_, _) => "Cannot read from script file",
+            Self::ErrorReadingScriptFile(_, _, _) => "Cannot read from script file",
 
             Self::ErrorParsing(p) => p.desc(),
             Self::ErrorFunctionNotFound(_, _) => "Function not found",
@@ -150,9 +150,13 @@ impl fmt::Display for EvalAltResult {
 
         match self {
             #[cfg(not(feature = "no_std"))]
-            Self::ErrorReadingScriptFile(path, err) => {
+            Self::ErrorReadingScriptFile(path, pos, err) if pos.is_none() => {
                 write!(f, "{} '{}': {}", desc, path.display(), err)
             }
+            #[cfg(not(feature = "no_std"))]
+            Self::ErrorReadingScriptFile(path, pos, err) => {
+                write!(f, "{} '{}': {} ({})", desc, path.display(), err, pos)
+            }
 
             Self::ErrorParsing(p) => write!(f, "Syntax error: {}", p),
 
@@ -261,7 +265,7 @@ impl EvalAltResult {
     pub fn position(&self) -> Position {
         match self {
             #[cfg(not(feature = "no_std"))]
-            Self::ErrorReadingScriptFile(_, _) => Position::none(),
+            Self::ErrorReadingScriptFile(_, pos, _) => *pos,
 
             Self::ErrorParsing(err) => err.position(),
 
@@ -297,7 +301,7 @@ impl EvalAltResult {
     pub(crate) fn set_position(mut err: Box<Self>, new_position: Position) -> Box<Self> {
         match err.as_mut() {
             #[cfg(not(feature = "no_std"))]
-            Self::ErrorReadingScriptFile(_, _) => (),
+            Self::ErrorReadingScriptFile(_, pos, _) => *pos = new_position,
 
             Self::ErrorParsing(err) => err.1 = new_position,