core: Remove GraphWalkerPanicwrap, etc

These are some remnants of the shadow graph functionality that was added
to support the graph builder changes in v0.8, but that has since been
removed and so there are no remaining callers for these types and
functions.

terraform/graph.go

@@ -3,7 +3,6 @@ package terraform
 import (
 	"fmt"
 	"log"
-	"runtime/debug"
 
 	"github.com/hashicorp/terraform/tfdiags"
 
@@ -47,12 +46,6 @@ func (g *Graph) walk(walker GraphWalker) tfdiags.Diagnostics {
 	// Get the path for logs
 	path := ctx.Path().String()
 
-	// Determine if our walker is a panic wrapper
-	panicwrap, ok := walker.(GraphWalkerPanicwrapper)
-	if !ok {
-		panicwrap = nil // just to be sure
-	}
-
 	debugName := "walk-graph.json"
 	if g.debugName != "" {
 		debugName = g.debugName + "-" + debugName
@@ -68,28 +61,8 @@ func (g *Graph) walk(walker GraphWalker) tfdiags.Diagnostics {
 		log.Printf("[TRACE] vertex %q: starting visit (%T)", dag.VertexName(v), v)
 		g.DebugVisitInfo(v, g.debugName)
 
-		// If we have a panic wrap GraphWalker and a panic occurs, recover
-		// and call that. We ensure the return value is an error, however,
-		// so that future nodes are not called.
 		defer func() {
 			log.Printf("[TRACE] vertex %q: visit complete", dag.VertexName(v))
-
-			// If no panicwrap, do nothing
-			if panicwrap == nil {
-				return
-			}
-
-			// If no panic, do nothing
-			err := recover()
-			if err == nil {
-				return
-			}
-
-			// Modify the return value to show the error
-			diags = diags.Append(fmt.Errorf("vertex %q captured panic: %s\n\n%s", dag.VertexName(v), err, debug.Stack()))
-
-			// Call the panic wrapper
-			panicwrap.Panic(v, err)
 		}()
 
 		walker.EnterVertex(v)

terraform/graph_test.go

@@ -6,23 +6,6 @@ import (
 	"github.com/hashicorp/terraform/dag"
 )
 
-func TestGraphWalk_panicWrap(t *testing.T) {
-	var g Graph
-
-	// Add our crasher
-	v := &testGraphSubPath{
-		PathFn: func() []string {
-			panic("yo")
-		},
-	}
-	g.Add(v)
-
-	err := g.Walk(GraphWalkerPanicwrap(new(NullGraphWalker)))
-	if err == nil {
-		t.Fatal("should error")
-	}
-}
-
 // testGraphContains is an assertion helper that tests that a node is
 // contained in the graph.
 func testGraphContains(t *testing.T, g *Graph, name string) {

terraform/graph_walk.go

@@ -17,36 +17,6 @@ type GraphWalker interface {
 	ExitEvalTree(dag.Vertex, interface{}, error) tfdiags.Diagnostics
 }
 
-// GrpahWalkerPanicwrapper can be optionally implemented to catch panics
-// that occur while walking the graph. This is not generally recommended
-// since panics should crash Terraform and result in a bug report. However,
-// this is particularly useful for situations like the shadow graph where
-// you don't ever want to cause a panic.
-type GraphWalkerPanicwrapper interface {
-	GraphWalker
-
-	// Panic is called when a panic occurs. This will halt the panic from
-	// propogating so if the walker wants it to crash still it should panic
-	// again. This is called from within a defer so runtime/debug.Stack can
-	// be used to get the stack trace of the panic.
-	Panic(dag.Vertex, interface{})
-}
-
-// GraphWalkerPanicwrap wraps an existing Graphwalker to wrap and swallow
-// the panics. This doesn't lose the panics since the panics are still
-// returned as errors as part of a graph walk.
-func GraphWalkerPanicwrap(w GraphWalker) GraphWalkerPanicwrapper {
-	return &graphWalkerPanicwrapper{
-		GraphWalker: w,
-	}
-}
-
-type graphWalkerPanicwrapper struct {
-	GraphWalker
-}
-
-func (graphWalkerPanicwrapper) Panic(dag.Vertex, interface{}) {}
-
 // NullGraphWalker is a GraphWalker implementation that does nothing.
 // This can be embedded within other GraphWalker implementations for easily
 // implementing all the required functions.