Remove spirv result from Error::display (#20)

* Checkpoint fix for #19

* Ignore the spirv error code when in Error::display

This is due to the lossiness of running the spirv binaries, while
needing (more) consistent error output between compiled and tool.

src/cmd.rs

@@ -48,7 +48,10 @@ impl From<CmdError> for crate::error::Error {
                 );
 
                 Self {
-                    inner: SpirvResult::InternalError, // this isn't really correct
+                    // this isn't really correct, but the spirv binaries don't
+                    // provide the error code in any meaningful way, either by the
+                    // status code of the binary, or in diagnostic output
+                    inner: SpirvResult::InternalError,
                     diagnostic: Some(diagnostic),
                 }
             }

src/error.rs

@@ -15,10 +15,10 @@ impl fmt::Display for Error {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match &self.diagnostic {
             Some(diag) => f.write_fmt(format_args!(
-                "{}:{}:{} - {}",
-                self.inner, diag.line, diag.column, diag.message
+                "error:{}:{} - {}",
+                diag.line, diag.column, diag.message
             )),
-            None => f.write_fmt(format_args!("{}", self.inner)),
+            None => f.write_str("an unknown error occurred"),
         }
     }
 }

tests/val.rs

@@ -26,14 +26,16 @@ fn validate_tool(_input: &[u8]) -> Option<Result<(), spirv_tools::Error>> {
 
 #[test]
 fn gets_error_message() {
-    let cexpected_msg = "invalid cfg:0:0 - Loop header 6[%loop_header] is targeted by 2 back-edge blocks but the standard requires exactly one\n  %loop_header = OpLabel\n";
-    let texpected_msg = "internal error:0:0 - Loop header 6[%loop_header] is targeted by 2 back-edge blocks but the standard requires exactly one";
+    let cexpected_msg = "error:0:0 - Loop header 6[%loop_header] is targeted by 2 back-edge blocks but the standard requires exactly one\n  %loop_header = OpLabel\n";
+    let texpected_msg = "error:0:0 - Loop header 6[%loop_header] is targeted by 2 back-edge blocks but the standard requires exactly one";
     match (validate_compiled(SPIRV_BIN), validate_tool(SPIRV_BIN)) {
         (Some(resc), Some(rest)) => {
-            // assert_eq!(resc, rest);
+            let cstr = resc.unwrap_err().to_string();
+            let tstr = rest.unwrap_err().to_string();
+            assert_eq!(&cstr[..111], &tstr[..111]);
 
-            assert_eq!(resc.unwrap_err().to_string(), cexpected_msg);
-            assert_eq!(rest.unwrap_err().to_string(), texpected_msg);
+            assert_eq!(cstr, cexpected_msg);
+            assert_eq!(tstr, texpected_msg);
         }
         (Some(resc), None) => {
             assert_eq!(resc.unwrap_err().to_string(), cexpected_msg);