opentofu/terraform/graph.go
Kristin Laemmert 883e4487a2
terraform: add GraphNodeExecutable interface (#26132)
This introduces a new GraphNode, GraphNodeExecutable, which will
gradually replace GraphNodeEvalable as part of the overall removal of
EvalTree()s. Terraform's Graph.walk function will now check if a node is
GraphNodeExecutable and run walker.Execute instead of running through
the EvalTree() and Eval().

For the time being, terraform will panic if a node implements both
GraphNodeExecutable and GraphNodeEvalable. This will be removed when
we've finished removing all GraphNodeEvalable implementations.

The new GraphWalker function, Execute(), is meant to replace both
EnterEvalTree and ExitEvalTree, and wraps the call to the
GraphNodeExecutable's Execute function.
2020-09-04 14:03:45 -04:00

120 lines
3.4 KiB
Go

package terraform
import (
"fmt"
"log"
"github.com/hashicorp/terraform/tfdiags"
"github.com/hashicorp/terraform/addrs"
"github.com/hashicorp/terraform/dag"
)
// Graph represents the graph that Terraform uses to represent resources
// and their dependencies.
type Graph struct {
// Graph is the actual DAG. This is embedded so you can call the DAG
// methods directly.
dag.AcyclicGraph
// Path is the path in the module tree that this Graph represents.
Path addrs.ModuleInstance
}
func (g *Graph) DirectedGraph() dag.Grapher {
return &g.AcyclicGraph
}
// Walk walks the graph with the given walker for callbacks. The graph
// will be walked with full parallelism, so the walker should expect
// to be called in concurrently.
func (g *Graph) Walk(walker GraphWalker) tfdiags.Diagnostics {
return g.walk(walker)
}
func (g *Graph) walk(walker GraphWalker) tfdiags.Diagnostics {
// The callbacks for enter/exiting a graph
ctx := walker.EvalContext()
// Walk the graph.
var walkFn dag.WalkFunc
walkFn = func(v dag.Vertex) (diags tfdiags.Diagnostics) {
log.Printf("[TRACE] vertex %q: starting visit (%T)", dag.VertexName(v), v)
defer func() {
log.Printf("[TRACE] vertex %q: visit complete", dag.VertexName(v))
}()
// vertexCtx is the context that we use when evaluating. This
// is normally the context of our graph but can be overridden
// with a GraphNodeModuleInstance impl.
vertexCtx := ctx
if pn, ok := v.(GraphNodeModuleInstance); ok {
vertexCtx = walker.EnterPath(pn.Path())
defer walker.ExitPath(pn.Path())
}
// If the node is exec-able, then execute it.
if ev, ok := v.(GraphNodeExecutable); ok {
// A node must not be both Evalable and Executable. This will be
// removed when GraphNodeEvalable is fully removed.
if _, ok := v.(GraphNodeEvalable); ok {
panic(fmt.Sprintf(
"%T implements both GraphNodeEvalable and GraphNodeExecutable", v,
))
}
diags = diags.Append(walker.Execute(vertexCtx, ev))
if diags.HasErrors() {
return
}
}
// If the node is eval-able, then evaluate it.
if ev, ok := v.(GraphNodeEvalable); ok {
tree := ev.EvalTree()
if tree == nil {
panic(fmt.Sprintf("%q (%T): nil eval tree", dag.VertexName(v), v))
}
// Allow the walker to change our tree if needed. Eval,
// then callback with the output.
log.Printf("[TRACE] vertex %q: evaluating", dag.VertexName(v))
tree = walker.EnterEvalTree(v, tree)
output, err := Eval(tree, vertexCtx)
diags = diags.Append(walker.ExitEvalTree(v, output, err))
if diags.HasErrors() {
return
}
}
// If the node is dynamically expanded, then expand it
if ev, ok := v.(GraphNodeDynamicExpandable); ok {
log.Printf("[TRACE] vertex %q: expanding dynamic subgraph", dag.VertexName(v))
g, err := ev.DynamicExpand(vertexCtx)
if err != nil {
diags = diags.Append(err)
return
}
if g != nil {
// Walk the subgraph
log.Printf("[TRACE] vertex %q: entering dynamic subgraph", dag.VertexName(v))
subDiags := g.walk(walker)
diags = diags.Append(subDiags)
if subDiags.HasErrors() {
log.Printf("[TRACE] vertex %q: dynamic subgraph encountered errors", dag.VertexName(v))
return
}
log.Printf("[TRACE] vertex %q: dynamic subgraph completed successfully", dag.VertexName(v))
} else {
log.Printf("[TRACE] vertex %q: produced no dynamic subgraph", dag.VertexName(v))
}
}
return
}
return g.AcyclicGraph.Walk(walkFn)
}