topdown: Add trace event when value is resolved externally

When an external resolver is used we will emit a new type of trace event. While not providing a ton of details (for now) it does at least give some hints as to what happened with the evaluation. Signed-off-by: Patrick East <[email protected]>
b-xiang · Nov 6, 2020 · 73efebd · 73efebd
1 parent ee7f123
commit 73efebd
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Showing 2 changed files with 11 additions and 1 deletion.
diff --git a/topdown/eval.go b/topdown/eval.go
@@ -178,6 +178,10 @@ func (e *eval) traceIndex(x ast.Node, msg string) {
 	e.traceEvent(IndexOp, x, msg)
 }
 
+func (e *eval) traceExternalResolve(x ast.Node) {
+	e.traceEvent(ExternalResolveOp, x, "")
+}
+
 func (e *eval) traceEvent(op Op, x ast.Node, msg string) {
 
 	if !e.traceEnabled {
@@ -1330,7 +1334,9 @@ func (e *eval) resolveReadFromStorage(ref ast.Ref, a ast.Value) (ast.Value, erro
 
 	if err != nil {
 		return nil, err
-	} else if v == nil {
+	} else if v != nil {
+		e.traceExternalResolve(e.query[e.index])
+	} else {
 
 		path, err := storage.NewPathForRef(ref)
 		if err != nil {

diff --git a/topdown/trace.go b/topdown/trace.go
@@ -50,6 +50,10 @@ const (
 	// IndexOp is emitted during an expression evaluation to represent lookup
 	// matches.
 	IndexOp Op = "Index"
+
+	// ExternalResolveOp is emitted when resolving a ref using an external
+	// Resolver.
+	ExternalResolveOp Op = "ExternalResolve"
 )
 
 // VarMetadata provides some user facing information about