terraform: GraphWalkerPanicwrap catches panics during graph walks
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@ -3,6 +3,7 @@ package terraform
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import (
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import (
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"fmt"
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"fmt"
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"log"
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"log"
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"runtime/debug"
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"strings"
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"strings"
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"sync"
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"sync"
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@ -217,11 +218,40 @@ func (g *Graph) walk(walker GraphWalker) error {
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// Get the path for logs
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// Get the path for logs
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path := strings.Join(ctx.Path(), ".")
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path := strings.Join(ctx.Path(), ".")
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// Determine if our walker is a panic wrapper
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panicwrap, ok := walker.(GraphWalkerPanicwrapper)
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if !ok {
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panicwrap = nil // just to be sure
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}
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// Walk the graph.
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// Walk the graph.
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var walkFn dag.WalkFunc
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var walkFn dag.WalkFunc
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walkFn = func(v dag.Vertex) (rerr error) {
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walkFn = func(v dag.Vertex) (rerr error) {
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log.Printf("[DEBUG] vertex '%s.%s': walking", path, dag.VertexName(v))
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log.Printf("[DEBUG] vertex '%s.%s': walking", path, dag.VertexName(v))
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// If we have a panic wrap GraphWalker and a panic occurs, recover
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// and call that. We ensure the return value is an error, however,
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// so that future nodes are not called.
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defer func() {
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// If no panicwrap, do nothing
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if panicwrap == nil {
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return
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}
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// If no panic, do nothing
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err := recover()
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if err == nil {
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return
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}
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// Modify the return value to show the error
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rerr = fmt.Errorf("vertex %q captured panic: %s\n\n%s",
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dag.VertexName(v), err, debug.Stack())
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// Call the panic wrapper
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panicwrap.Panic(v, err)
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}()
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walker.EnterVertex(v)
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walker.EnterVertex(v)
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defer func() { walker.ExitVertex(v, rerr) }()
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defer func() { walker.ExitVertex(v, rerr) }()
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@ -69,6 +69,29 @@ func TestGraphReplace_DependableWithNonDependable(t *testing.T) {
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}
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}
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}
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}
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func TestGraphWalk_panicWrap(t *testing.T) {
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var g Graph
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// Add our crasher
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v := &testGraphSubPath{
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PathFn: func() []string {
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panic("yo")
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},
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}
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g.Add(v)
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err := g.Walk(GraphWalkerPanicwrap(new(NullGraphWalker)))
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if err == nil {
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t.Fatal("should error")
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}
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}
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type testGraphSubPath struct {
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PathFn func() []string
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}
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func (v *testGraphSubPath) Path() []string { return v.PathFn() }
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type testGraphDependable struct {
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type testGraphDependable struct {
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VertexName string
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VertexName string
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DependentOnMock []string
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DependentOnMock []string
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@ -15,12 +15,42 @@ type GraphWalker interface {
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ExitEvalTree(dag.Vertex, interface{}, error) error
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ExitEvalTree(dag.Vertex, interface{}, error) error
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}
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}
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// GrpahWalkerPanicwrapper can be optionally implemented to catch panics
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// that occur while walking the graph. This is not generally recommended
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// since panics should crash Terraform and result in a bug report. However,
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// this is particularly useful for situations like the shadow graph where
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// you don't ever want to cause a panic.
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type GraphWalkerPanicwrapper interface {
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GraphWalker
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// Panic is called when a panic occurs. This will halt the panic from
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// propogating so if the walker wants it to crash still it should panic
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// again. This is called from within a defer so runtime/debug.Stack can
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// be used to get the stack trace of the panic.
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Panic(dag.Vertex, interface{})
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}
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// GraphWalkerPanicwrap wraps an existing Graphwalker to wrap and swallow
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// the panics. This doesn't lose the panics since the panics are still
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// returned as errors as part of a graph walk.
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func GraphWalkerPanicwrap(w GraphWalker) GraphWalkerPanicwrapper {
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return &graphWalkerPanicwrapper{
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GraphWalker: w,
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}
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}
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type graphWalkerPanicwrapper struct {
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GraphWalker
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}
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func (graphWalkerPanicwrapper) Panic(dag.Vertex, interface{}) {}
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// NullGraphWalker is a GraphWalker implementation that does nothing.
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// NullGraphWalker is a GraphWalker implementation that does nothing.
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// This can be embedded within other GraphWalker implementations for easily
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// This can be embedded within other GraphWalker implementations for easily
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// implementing all the required functions.
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// implementing all the required functions.
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type NullGraphWalker struct{}
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type NullGraphWalker struct{}
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func (NullGraphWalker) EnterPath([]string) EvalContext { return nil }
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func (NullGraphWalker) EnterPath([]string) EvalContext { return new(MockEvalContext) }
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func (NullGraphWalker) ExitPath([]string) {}
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func (NullGraphWalker) ExitPath([]string) {}
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func (NullGraphWalker) EnterVertex(dag.Vertex) {}
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func (NullGraphWalker) EnterVertex(dag.Vertex) {}
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func (NullGraphWalker) ExitVertex(dag.Vertex, error) {}
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func (NullGraphWalker) ExitVertex(dag.Vertex, error) {}
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