From c711cd750646d12ee0f8ccdfe77199da94a267f5 Mon Sep 17 00:00:00 2001
From: Flavio Castelli <fcastelli@suse.com>
Date: Tue, 12 Dec 2023 09:40:53 +0100
Subject: [PATCH] fix: improve error message

Provide a better error message when performing the OPA/Gatekeeper
detection.

This is is a follow up from issue https://github.com/kubewarden/kwctl/issues/662

Signed-off-by: Flavio Castelli <fcastelli@suse.com>
---
 src/backend.rs | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/src/backend.rs b/src/backend.rs
index 527c1d24..716e01bf 100644
--- a/src/backend.rs
+++ b/src/backend.rs
@@ -22,18 +22,25 @@ pub(crate) enum Backend {
 type KubewardenProtocolDetectorFn = fn(PathBuf) -> Result<ProtocolVersion>;
 type RegoDetectorFn = fn(PathBuf) -> Result<bool>;
 
-// Looks at the Wasm module pointed by `wasm_path` and return whether it was generaed by a Rego
+// Looks at the Wasm module pointed by `wasm_path` and return whether it was generated by a Rego
 // policy
 //
 // The code looks at the export symbols offered by the Wasm module.
 // Having at least one symbol that starts with the `opa_` prefix leads
 // the policy to be considered a Rego-based one.
 fn rego_policy_detector(wasm_path: PathBuf) -> Result<bool> {
-    let data: Vec<u8> = std::fs::read(wasm_path)?;
+    let data: Vec<u8> = std::fs::read(wasm_path.clone())
+        .map_err(|e| anyhow!("cannot access file {:?}: {}", wasm_path, e))?;
     for payload in wasmparser::Parser::new(0).parse_all(&data) {
-        if let wasmparser::Payload::ExportSection(s) = payload? {
+        if let wasmparser::Payload::ExportSection(s) =
+            payload.map_err(|e| anyhow!("cannot parse WebAssembly file: {}", e))?
+        {
             for export in s {
-                if export?.name.starts_with("opa_") {
+                if export
+                    .map_err(|e| anyhow!("cannot parse WebAssembly export section: {}", e))?
+                    .name
+                    .starts_with("opa_")
+                {
                     return Ok(true);
                 }
             }
@@ -80,12 +87,8 @@ impl BackendDetector {
     }
 
     pub(crate) fn is_rego_policy(&self, wasm_path: &Path) -> Result<bool> {
-        (self.rego_detector_func)(wasm_path.to_path_buf()).map_err(|e| {
-            anyhow!(
-                "Error while checking if the policy has been created using Opa/Gatekeeper: {}",
-                e
-            )
-        })
+        (self.rego_detector_func)(wasm_path.to_path_buf())
+            .map_err(|e| anyhow!("Rego policy type check failure: {}", e))
     }
 
     pub(crate) fn detect(&self, wasm_path: PathBuf, metadata: &Metadata) -> Result<Backend> {