From d3d720babd6f3d59922457dda5935da64dd2fe4c Mon Sep 17 00:00:00 2001
From: Mark McCaskey <mark@wasmer.io>
Date: Mon, 6 Jan 2020 15:30:30 -0500
Subject: [PATCH] Improve formatting of error messages we display from wabt

---
 Cargo.lock        | 32 +++++++++++++++++++++++++++++---
 src/bin/wasmer.rs | 19 +++++++++++++++++--
 2 files changed, 46 insertions(+), 5 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index bcbe7400d..0f5d6d7c8 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -558,7 +558,7 @@ dependencies = [
  "libc",
  "llvm-sys",
  "once_cell",
- "parking_lot",
+ "parking_lot 0.10.0",
  "regex",
 ]
 
@@ -827,6 +827,17 @@ dependencies = [
  "md5",
 ]
 
+[[package]]
+name = "parking_lot"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f842b1982eb6c2fe34036a4fbfb06dd185a3f5c8edfaacdf7d1ea10b07de6252"
+dependencies = [
+ "lock_api",
+ "parking_lot_core 0.6.2",
+ "rustc_version",
+]
+
 [[package]]
 name = "parking_lot"
 version = "0.10.0"
@@ -834,7 +845,22 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "92e98c49ab0b7ce5b222f2cc9193fc4efe11c6d0bd4f648e374684a6857b1cfc"
 dependencies = [
  "lock_api",
- "parking_lot_core",
+ "parking_lot_core 0.7.0",
+]
+
+[[package]]
+name = "parking_lot_core"
+version = "0.6.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b876b1b9e7ac6e1a74a6da34d25c42e17e8862aa409cbbbdcfc8d86c6f3bc62b"
+dependencies = [
+ "cfg-if",
+ "cloudabi",
+ "libc",
+ "redox_syscall",
+ "rustc_version",
+ "smallvec 0.6.13",
+ "winapi",
 ]
 
 [[package]]
@@ -1761,7 +1787,7 @@ dependencies = [
  "libc",
  "nix",
  "page_size",
- "parking_lot",
+ "parking_lot 0.9.0",
  "rustc_version",
  "serde",
  "serde-bench",
diff --git a/src/bin/wasmer.rs b/src/bin/wasmer.rs
index 1c19e6082..04ef6d3a2 100644
--- a/src/bin/wasmer.rs
+++ b/src/bin/wasmer.rs
@@ -11,6 +11,7 @@ extern crate structopt;
 
 use std::collections::HashMap;
 use std::env;
+use std::error::Error;
 use std::fs::{metadata, read_to_string, File};
 use std::io;
 use std::io::Read;
@@ -623,8 +624,22 @@ fn execute_wasm(options: &Run) -> Result<(), String> {
 
     if !utils::is_wasm_binary(&wasm_binary) {
         let features = options.features.into_wabt_features();
-        wasm_binary = wabt::wat2wasm_with_features(wasm_binary, features)
-            .map_err(|e| format!("Can't convert from wast to wasm: {:?}", e))?;
+        wasm_binary = wabt::wat2wasm_with_features(wasm_binary, features).map_err(|e| {
+            format!(
+                "Can't convert from wast to wasm because \"{}\"{}",
+                e.description(),
+                match e.kind() {
+                    wabt::ErrorKind::Deserialize(s)
+                    | wabt::ErrorKind::Parse(s)
+                    | wabt::ErrorKind::ResolveNames(s)
+                    | wabt::ErrorKind::Validate(s) => format!(":\n\n{}", s),
+                    wabt::ErrorKind::Nul
+                    | wabt::ErrorKind::WriteText
+                    | wabt::ErrorKind::NonUtf8Result
+                    | wabt::ErrorKind::WriteBinary => "".to_string(),
+                }
+            )
+        })?;
     }
 
     let compiler: Box<dyn Compiler> = get_compiler_by_backend(options.backend, options)