Simple proposal to extend error handling. (#64)

* Simple proposal to extend error handling.

* Changing error to code.

---------

Co-authored-by: Stuart Schaefer <[email protected]>

Author: shschaefer

ml.md

@@ -90,16 +90,51 @@ memory--e.g., using row-major ordering--and could perhaps be improved.</p>
 <p>TODO: create function-specific errors (https://github.com/WebAssembly/wasi-nn/issues/42)</p>
 <hr />
 <h3>Types</h3>
-<h4><a name="error"><code>enum error</code></a></h4>
+<h4><a name="error_code"><code>enum error-code</code></a></h4>
 <h5>Enum Cases</h5>
 <ul>
-<li><a name="error.invalid_argument"><code>invalid-argument</code></a></li>
-<li><a name="error.invalid_encoding"><code>invalid-encoding</code></a></li>
-<li><a name="error.busy"><code>busy</code></a></li>
-<li><a name="error.runtime_error"><code>runtime-error</code></a></li>
-<li><a name="error.unsupported_operation"><code>unsupported-operation</code></a></li>
-<li><a name="error.too_large"><code>too-large</code></a></li>
-<li><a name="error.not_found"><code>not-found</code></a></li>
+<li><a name="error_code.invalid_argument"><code>invalid-argument</code></a></li>
+<li><a name="error_code.invalid_encoding"><code>invalid-encoding</code></a></li>
+<li><a name="error_code.timeout"><code>timeout</code></a></li>
+<li><a name="error_code.runtime_error"><code>runtime-error</code></a></li>
+<li><a name="error_code.unsupported_operation"><code>unsupported-operation</code></a></li>
+<li><a name="error_code.too_large"><code>too-large</code></a></li>
+<li><a name="error_code.not_found"><code>not-found</code></a></li>
+<li><a name="error_code.security"><code>security</code></a></li>
+<li><a name="error_code.unknown"><code>unknown</code></a></li>
+</ul>
+<h4><a name="error"><code>resource error</code></a></h4>
+<hr />
+<h3>Functions</h3>
+<h4><a name="constructor_error"><code>[constructor]error: func</code></a></h4>
+<h5>Params</h5>
+<ul>
+<li><a name="constructor_error.code"><code>code</code></a>: <a href="#error_code"><a href="#error_code"><code>error-code</code></a></a></li>
+<li><a name="constructor_error.data"><code>data</code></a>: <code>string</code></li>
+</ul>
+<h5>Return values</h5>
+<ul>
+<li><a name="constructor_error.0"></a> own&lt;<a href="#error"><a href="#error"><code>error</code></a></a>&gt;</li>
+</ul>
+<h4><a name="method_error.code"><code>[method]error.code: func</code></a></h4>
+<p>Return the error code.</p>
+<h5>Params</h5>
+<ul>
+<li><a name="method_error.code.self"><code>self</code></a>: borrow&lt;<a href="#error"><a href="#error"><code>error</code></a></a>&gt;</li>
+</ul>
+<h5>Return values</h5>
+<ul>
+<li><a name="method_error.code.0"></a> <a href="#error_code"><a href="#error_code"><code>error-code</code></a></a></li>
+</ul>
+<h4><a name="method_error.data"><code>[method]error.data: func</code></a></h4>
+<p>Errors can propagated with backend specific status through a string value.</p>
+<h5>Params</h5>
+<ul>
+<li><a name="method_error.data.self"><code>self</code></a>: borrow&lt;<a href="#error"><a href="#error"><code>error</code></a></a>&gt;</li>
+</ul>
+<h5>Return values</h5>
+<ul>
+<li><a name="method_error.data.0"></a> <code>string</code></li>
 </ul>
 <h2><a name="wasi:nn_inference">Import interface wasi:nn/inference</a></h2>
 <p>An inference &quot;session&quot; is encapsulated by a <a href="#graph_execution_context"><code>graph-execution-context</code></a>. This structure binds a
@@ -128,7 +163,7 @@ memory--e.g., using row-major ordering--and could perhaps be improved.</p>
 </ul>
 <h5>Return values</h5>
 <ul>
-<li><a name="method_graph_execution_context.set_input.0"></a> result&lt;_, <a href="#error"><a href="#error"><code>error</code></a></a>&gt;</li>
+<li><a name="method_graph_execution_context.set_input.0"></a> result&lt;_, own&lt;<a href="#error"><a href="#error"><code>error</code></a></a>&gt;&gt;</li>
 </ul>
 <h4><a name="method_graph_execution_context.compute"><code>[method]graph-execution-context.compute: func</code></a></h4>
 <p>Compute the inference on the given inputs.</p>
@@ -141,7 +176,7 @@ https://github.com/WebAssembly/wasi-nn/issues/43.</p>
 </ul>
 <h5>Return values</h5>
 <ul>
-<li><a name="method_graph_execution_context.compute.0"></a> result&lt;_, <a href="#error"><a href="#error"><code>error</code></a></a>&gt;</li>
+<li><a name="method_graph_execution_context.compute.0"></a> result&lt;_, own&lt;<a href="#error"><a href="#error"><code>error</code></a></a>&gt;&gt;</li>
 </ul>
 <h4><a name="method_graph_execution_context.get_output"><code>[method]graph-execution-context.get-output: func</code></a></h4>
 <p>Extract the outputs after inference.</p>
@@ -152,7 +187,7 @@ https://github.com/WebAssembly/wasi-nn/issues/43.</p>
 </ul>
 <h5>Return values</h5>
 <ul>
-<li><a name="method_graph_execution_context.get_output.0"></a> result&lt;own&lt;<a href="#tensor"><a href="#tensor"><code>tensor</code></a></a>&gt;, <a href="#error"><a href="#error"><code>error</code></a></a>&gt;</li>
+<li><a name="method_graph_execution_context.get_output.0"></a> result&lt;own&lt;<a href="#tensor"><a href="#tensor"><code>tensor</code></a></a>&gt;, own&lt;<a href="#error"><a href="#error"><code>error</code></a></a>&gt;&gt;</li>
 </ul>
 <h2><a name="wasi:nn_graph">Import interface wasi:nn/graph</a></h2>
 <p>A <a href="#graph"><code>graph</code></a> is a loaded instance of a specific ML model (e.g., MobileNet) for a specific ML
@@ -203,7 +238,7 @@ graph IR in parts (e.g., OpenVINO stores its IR and weights separately).</p>
 </ul>
 <h5>Return values</h5>
 <ul>
-<li><a name="method_graph.init_execution_context.0"></a> result&lt;own&lt;<a href="#graph_execution_context"><a href="#graph_execution_context"><code>graph-execution-context</code></a></a>&gt;, <a href="#error"><a href="#error"><code>error</code></a></a>&gt;</li>
+<li><a name="method_graph.init_execution_context.0"></a> result&lt;own&lt;<a href="#graph_execution_context"><a href="#graph_execution_context"><code>graph-execution-context</code></a></a>&gt;, own&lt;<a href="#error"><a href="#error"><code>error</code></a></a>&gt;&gt;</li>
 </ul>
 <h4><a name="load"><code>load: func</code></a></h4>
 <p>Load a <a href="#graph"><code>graph</code></a> from an opaque sequence of bytes to use for inference.</p>
@@ -215,7 +250,7 @@ graph IR in parts (e.g., OpenVINO stores its IR and weights separately).</p>
 </ul>
 <h5>Return values</h5>
 <ul>
-<li><a name="load.0"></a> result&lt;own&lt;<a href="#graph"><a href="#graph"><code>graph</code></a></a>&gt;, <a href="#error"><a href="#error"><code>error</code></a></a>&gt;</li>
+<li><a name="load.0"></a> result&lt;own&lt;<a href="#graph"><a href="#graph"><code>graph</code></a></a>&gt;, own&lt;<a href="#error"><a href="#error"><code>error</code></a></a>&gt;&gt;</li>
 </ul>
 <h4><a name="load_by_name"><code>load-by-name: func</code></a></h4>
 <p>Load a <a href="#graph"><code>graph</code></a> by name.</p>
@@ -228,5 +263,5 @@ range from simple to complex (e.g., URLs?) and caching mechanisms of various kin
 </ul>
 <h5>Return values</h5>
 <ul>
-<li><a name="load_by_name.0"></a> result&lt;own&lt;<a href="#graph"><a href="#graph"><code>graph</code></a></a>&gt;, <a href="#error"><a href="#error"><code>error</code></a></a>&gt;</li>
+<li><a name="load_by_name.0"></a> result&lt;own&lt;<a href="#graph"><a href="#graph"><code>graph</code></a></a>&gt;, own&lt;<a href="#error"><a href="#error"><code>error</code></a></a>&gt;&gt;</li>
 </ul>

wit/wasi-nn.wit

@@ -133,19 +133,35 @@ interface inference {
 
 /// TODO: create function-specific errors (https://github.com/WebAssembly/wasi-nn/issues/42)
 interface errors {
-    enum error {
+    enum error-code {
         // Caller module passed an invalid argument.
         invalid-argument,
         // Invalid encoding.
         invalid-encoding,
-        busy,
+        // The operation timed out.
+        timeout,
         // Runtime Error.
         runtime-error,
         // Unsupported operation.
         unsupported-operation,
         // Graph is too large.
         too-large,
         // Graph not found.
-        not-found
+        not-found,
+        // The operation is insecure or has insufficient privilege to be performed.
+        // e.g., cannot access a hardware feature requested
+        security,
+        // The operation failed for an unspecified reason.
+        unknown
+    }
+
+    resource error {
+        constructor(code: error-code, data: string);
+
+        /// Return the error code.
+        code: func() -> error-code;
+
+        /// Errors can propagated with backend specific status through a string value.
+        data: func() -> string;
     }
 }