`import "github.com/hashicorp/terraform/dag"`

- func StronglyConnected(g *Graph) [][]Vertex
- func VertexName(raw Vertex) string
- type AcyclicGraph
- func (g *AcyclicGraph) Ancestors(v Vertex) (Set, error)
- func (g *AcyclicGraph) Cycles() [][]Vertex
- func (g *AcyclicGraph) DepthFirstWalk(start Set, f DepthWalkFunc) error
- func (g *AcyclicGraph) Descendents(v Vertex) (Set, error)
- func (g *AcyclicGraph) DirectedGraph() Grapher
- func (g *AcyclicGraph) ReverseDepthFirstWalk(start Set, f DepthWalkFunc) error
- func (g *AcyclicGraph) Root() (Vertex, error)
- func (g *AcyclicGraph) SortedDepthFirstWalk(start []Vertex, f DepthWalkFunc) error
- func (g *AcyclicGraph) SortedReverseDepthFirstWalk(start []Vertex, f DepthWalkFunc) error
- func (g *AcyclicGraph) TransitiveReduction()
- func (g *AcyclicGraph) Validate() error
- func (g *AcyclicGraph) Walk(cb WalkFunc) tfdiags.Diagnostics
- type DepthWalkFunc
- type DotNode
- type DotOpts
- type Edge
- type Graph
- func (g *Graph) Add(v Vertex) Vertex
- func (g *Graph) Connect(edge Edge)
- func (g *Graph) DirectedGraph() Grapher
- func (g *Graph) Dot(opts *DotOpts) []byte
- func (g *Graph) DownEdges(v Vertex) Set
- func (g *Graph) Edges() []Edge
- func (g *Graph) EdgesFrom(v Vertex) []Edge
- func (g *Graph) EdgesTo(v Vertex) []Edge
- func (g *Graph) HasEdge(e Edge) bool
- func (g *Graph) HasVertex(v Vertex) bool
- func (g *Graph) Remove(v Vertex) Vertex
- func (g *Graph) RemoveEdge(edge Edge)
- func (g *Graph) Replace(original, replacement Vertex) bool
- func (g *Graph) String() string
- func (g *Graph) StringWithNodeTypes() string
- func (g *Graph) UpEdges(v Vertex) Set
- func (g *Graph) Vertices() []Vertex
- type GraphNodeDotter
- type Grapher
- type Hashable
- type NamedVertex
- type Set
- func (s Set) Add(v interface{})
- func (s Set) Delete(v interface{})
- func (s Set) Difference(other Set) Set
- func (s Set) Filter(cb func(interface{}) bool) Set
- func (s Set) Include(v interface{}) bool
- func (s Set) Intersection(other Set) Set
- func (s Set) Len() int
- func (s Set) List() []interface{}
- type Subgrapher
- type Vertex
- type WalkFunc
- type Walker

dag.go dot.go edge.go graph.go marshal.go set.go tarjan.go walk.go

StronglyConnected returns the list of strongly connected components within the Graph g. This information is primarily used by this package for cycle detection, but strongly connected components have widespread use.

VertexName returns the name of a vertex.

AcyclicGraph is a specialization of Graph that cannot have cycles. With this property, we get the property of sane graph traversal.

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func (g *AcyclicGraph) Ancestors(v Vertex) (Set, error)

Returns a Set that includes every Vertex yielded by walking down from the provided starting Vertex v.

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func (g *AcyclicGraph) Cycles() [][]Vertex

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func (g *AcyclicGraph) DepthFirstWalk(start Set, f DepthWalkFunc) error

DepthFirstWalk does a depth-first walk of the graph starting from the vertices in start.

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func (g *AcyclicGraph) Descendents(v Vertex) (Set, error)

Returns a Set that includes every Vertex yielded by walking up from the provided starting Vertex v.

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func (g *AcyclicGraph) DirectedGraph() Grapher

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func (g *AcyclicGraph) ReverseDepthFirstWalk(start Set, f DepthWalkFunc) error

ReverseDepthFirstWalk does a depth-first walk _up_ the graph starting from the vertices in start.

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func (g *AcyclicGraph) Root() (Vertex, error)

Root returns the root of the DAG, or an error.

Complexity: O(V)

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func (g *AcyclicGraph) SortedDepthFirstWalk(start []Vertex, f DepthWalkFunc) error

SortedDepthFirstWalk does a depth-first walk of the graph starting from the vertices in start, always iterating the nodes in a consistent order.

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func (g *AcyclicGraph) SortedReverseDepthFirstWalk(start []Vertex, f DepthWalkFunc) error

SortedReverseDepthFirstWalk does a depth-first walk _up_ the graph starting from the vertices in start, always iterating the nodes in a consistent order.

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func (g *AcyclicGraph) TransitiveReduction()

TransitiveReduction performs the transitive reduction of graph g in place. The transitive reduction of a graph is a graph with as few edges as possible with the same reachability as the original graph. This means that if there are three nodes A => B => C, and A connects to both B and C, and B connects to C, then the transitive reduction is the same graph with only a single edge between A and B, and a single edge between B and C.

The graph must be valid for this operation to behave properly. If Validate() returns an error, the behavior is undefined and the results will likely be unexpected.

Complexity: O(V(V+E)), or asymptotically O(VE)

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func (g *AcyclicGraph) Validate() error

Validate validates the DAG. A DAG is valid if it has a single root with no cycles.

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func (g *AcyclicGraph) Walk(cb WalkFunc) tfdiags.Diagnostics

Walk walks the graph, calling your callback as each node is visited. This will walk nodes in parallel if it can. The resulting diagnostics contains problems from all graphs visited, in no particular order.

DepthWalkFunc is a walk function that also receives the current depth of the walk as an argument

DotNode provides a structure for Vertices to return in order to specify their dot format.

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type DotOpts struct { // Allows some nodes to decide to only show themselves when the user has // requested the "verbose" graph. Verbose bool // Highlight Cycles DrawCycles bool // How many levels to expand modules as we draw MaxDepth int // contains filtered or unexported fields }

DotOpts are the options for generating a dot formatted Graph.

Edge represents an edge in the graph, with a source and target vertex.

BasicEdge returns an Edge implementation that simply tracks the source and target given as-is.

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```
type Graph struct {
// contains filtered or unexported fields
}
```

Graph is used to represent a dependency graph.

Add adds a vertex to the graph. This is safe to call multiple time with the same Vertex.

Connect adds an edge with the given source and target. This is safe to call multiple times with the same value. Note that the same value is verified through pointer equality of the vertices, not through the value of the edge itself.

Dot returns a dot-formatted representation of the Graph.

DownEdges returns the outward edges from the source Vertex v.

Edges returns the list of all the edges in the graph.

EdgesFrom returns the list of edges from the given source.

EdgesTo returns the list of edges to the given target.

HasEdge checks if the given Edge is present in the graph.

HasVertex checks if the given Vertex is present in the graph.

Remove removes a vertex from the graph. This will also remove any edges with this vertex as a source or target.

RemoveEdge removes an edge from the graph.

Replace replaces the original Vertex with replacement. If the original does not exist within the graph, then false is returned. Otherwise, true is returned.

String outputs some human-friendly output for the graph structure.

String outputs some human-friendly output for the graph structure.

UpEdges returns the inward edges to the destination Vertex v.

Vertices returns the list of all the vertices in the graph.

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type GraphNodeDotter interface { // Dot is called to return the dot formatting for the node. // The first parameter is the title of the node. // The second parameter includes user-specified options that affect the dot // graph. See GraphDotOpts below for details. DotNode(string, *DotOpts) *DotNode }

GraphNodeDotter can be implemented by a node to cause it to be included in the dot graph. The Dot method will be called which is expected to return a representation of this node.

A Grapher is any type that returns a Grapher, mainly used to identify dag.Graph and dag.AcyclicGraph. In the case of Graph and AcyclicGraph, they return themselves.

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```
type Hashable interface {
Hashcode() interface{}
}
```

Hashable is the interface used by set to get the hash code of a value. If this isn't given, then the value of the item being added to the set itself is used as the comparison value.

NamedVertex is an optional interface that can be implemented by Vertex to give it a human-friendly name that is used for outputting the graph.

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type Set map[interface{}]interface{}

Set is a set data structure.

Add adds an item to the set

Delete removes an item from the set.

Difference returns a set with the elements that s has but other doesn't.

Filter returns a set that contains the elements from the receiver where the given callback returns true.

Include returns true/false of whether a value is in the set.

Intersection computes the set intersection with other.

Len is the number of items in the set.

List returns the list of set elements.

Subgrapher allows a Vertex to be a Graph itself, by returning a Grapher.

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type Vertex interface{}

Vertex of the graph.

simple convenience helper for converting a dag.Set to a []Vertex

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type WalkFunc func(Vertex) tfdiags.Diagnostics

WalkFunc is the callback used for walking the graph.

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type Walker struct { // Callback is what is called for each vertex Callback WalkFunc // Reverse, if true, causes the source of an edge to depend on a target. // When false (default), the target depends on the source. Reverse bool // contains filtered or unexported fields }

Walker is used to walk every vertex of a graph in parallel.

A vertex will only be walked when the dependencies of that vertex have been walked. If two vertices can be walked at the same time, they will be.

Update can be called to update the graph. This can be called even during a walk, changing vertices/edges mid-walk. This should be done carefully. If a vertex is removed but has already been executed, the result of that execution (any error) is still returned by Wait. Changing or re-adding a vertex that has already executed has no effect. Changing edges of a vertex that has already executed has no effect.

Non-parallelism can be enforced by introducing a lock in your callback function. However, the goroutine overhead of a walk will remain. Walker will create V*2 goroutines (one for each vertex, and dependency waiter for each vertex). In general this should be of no concern unless there are a huge number of vertices.

The walk is depth first by default. This can be changed with the Reverse option.

A single walker is only valid for one graph walk. After the walk is complete you must construct a new walker to walk again. State for the walk is never deleted in case vertices or edges are changed.

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func (w *Walker) Update(g *AcyclicGraph)

Update updates the currently executing walk with the given graph. This will perform a diff of the vertices and edges and update the walker. Already completed vertices remain completed (including any errors during their execution).

This returns immediately once the walker is updated; it does not wait for completion of the walk.

Multiple Updates can be called in parallel. Update can be called at any time during a walk.

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func (w *Walker) Wait() tfdiags.Diagnostics

Wait waits for the completion of the walk and returns diagnostics describing any problems that arose. Update should be called to populate the walk with vertices and edges prior to calling this.

Wait will return as soon as all currently known vertices are complete. If you plan on calling Update with more vertices in the future, you should not call Wait until after this is done.

Package dag imports 12 packages (graph) and is imported by 253 packages. Updated 2020-02-19. Refresh now. Tools for package owners.