From 3ad617fd690a13b95795783c1ef3c4d43a4377fb Mon Sep 17 00:00:00 2001
From: chenyukang <moorekang@gmail.com>
Date: Fri, 4 Jun 2021 15:40:37 +0800
Subject: [PATCH] fix unwrap error when given a no export functions wasm

---
 lib/cli/src/commands/run.rs        | 14 +++++++++-----
 tests/examples/no_start.wat        |  5 +++++
 tests/integration/cli/tests/run.rs | 18 ++++++++++++++++++
 3 files changed, 32 insertions(+), 5 deletions(-)
 create mode 100644 tests/examples/no_start.wat

diff --git a/lib/cli/src/commands/run.rs b/lib/cli/src/commands/run.rs
index f4b912087a6..c515c10f1f5 100644
--- a/lib/cli/src/commands/run.rs
+++ b/lib/cli/src/commands/run.rs
@@ -341,13 +341,17 @@ impl Run {
                     let suggested_command = format!(
                         "wasmer {} -i {} {}",
                         self.path.display(),
-                        suggested_functions.get(0).unwrap(),
+                        suggested_functions.get(0).unwrap_or(&String::new()),
                         args.join(" ")
                     );
-                    let suggestion = format!(
-                        "Similar functions found: {}.\nTry with: {}",
-                        names, suggested_command
-                    );
+                    let suggestion = if suggested_functions.len() == 0 {
+                        String::from("Can not find any export functions.")
+                    } else {
+                        format!(
+                            "Similar functions found: {}.\nTry with: {}",
+                            names, suggested_command
+                        )
+                    };
                     match e {
                         ExportError::Missing(_) => {
                             anyhow!("No export `{}` found in the module.\n{}", name, suggestion)
diff --git a/tests/examples/no_start.wat b/tests/examples/no_start.wat
new file mode 100644
index 00000000000..b6e7ee108c2
--- /dev/null
+++ b/tests/examples/no_start.wat
@@ -0,0 +1,5 @@
+(module
+  (type (;0;) (func (param f64) (result i32)))
+  (func (;0;) (type 0) (param f64) (result i32)
+    unreachable))
+
diff --git a/tests/integration/cli/tests/run.rs b/tests/integration/cli/tests/run.rs
index 7a2ed750eed..07fddc86564 100644
--- a/tests/integration/cli/tests/run.rs
+++ b/tests/integration/cli/tests/run.rs
@@ -12,6 +12,10 @@ fn test_no_imports_wat_path() -> String {
     format!("{}/{}", ASSET_PATH, "fib.wat")
 }
 
+fn test_no_start_wat_path() -> String {
+    format!("{}/{}", ASSET_PATH, "no_start.wat")
+}
+
 #[test]
 fn run_wasi_works() -> anyhow::Result<()> {
     let output = Command::new(WASMER_PATH)
@@ -39,6 +43,7 @@ fn run_wasi_works() -> anyhow::Result<()> {
 }
 
 #[test]
+
 fn run_no_imports_wasm_works() -> anyhow::Result<()> {
     let output = Command::new(WASMER_PATH)
         .arg("run")
@@ -57,3 +62,16 @@ fn run_no_imports_wasm_works() -> anyhow::Result<()> {
 
     Ok(())
 }
+
+#[test]
+fn run_no_start_wasm_report_error() -> anyhow::Result<()> {
+    let output = Command::new(WASMER_PATH)
+        .arg("run")
+        .arg(test_no_start_wat_path())
+        .output()?;
+
+    assert_eq!(output.status.success(), false);
+    let result = std::str::from_utf8(&output.stderr).unwrap().to_string();
+    assert_eq!(result.contains("Can not find any export functions."), true);
+    Ok(())
+}