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Some of the objects that are referencable from expressions are transient values computed only during a graph walk, and not persisted in state. In order to support arbitrary evaluation of expressions, such as in the "terraform console" CLI command, it's necessary to be able to evaluate these values before we start evaluating. This new Eval method achieves this by performing a special graph walk that ignores resources (except for dependency resolution) and just focuses on evaluating all of these transient values, before returning an evaluation scope that can then resolve expressions in terms of that result. This replaces the Context.Interpolator method, which was fraught with various issues due to it not properly priming the state before evaluating.
105 lines
3.1 KiB
Go
105 lines
3.1 KiB
Go
package terraform
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import (
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"github.com/hashicorp/terraform/dag"
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"github.com/hashicorp/terraform/tfdiags"
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"github.com/hashicorp/terraform/addrs"
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"github.com/hashicorp/terraform/configs"
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)
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// EvalGraphBuilder implements GraphBuilder and constructs a graph suitable
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// for evaluating in-memory values (input variables, local values, output
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// values) in the state without any other side-effects.
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//
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// This graph is used only in weird cases, such as the "terraform console"
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// CLI command, where we need to evaluate expressions against the state
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// without taking any other actions.
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//
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// The generated graph will include nodes for providers, resources, etc
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// just to allow indirect dependencies to be resolved, but these nodes will
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// not take any actions themselves since we assume that their parts of the
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// state, if any, are already complete.
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//
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// Although the providers are never configured, they must still be available
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// in order to obtain schema information used for type checking, etc.
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type EvalGraphBuilder struct {
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// Config is the configuration tree.
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Config *configs.Config
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// State is the current state
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State *State
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// Components is a factory for the plug-in components (providers and
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// provisioners) available for use.
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Components contextComponentFactory
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}
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// See GraphBuilder
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func (b *EvalGraphBuilder) Build(path addrs.ModuleInstance) (*Graph, tfdiags.Diagnostics) {
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return (&BasicGraphBuilder{
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Steps: b.Steps(),
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Validate: true,
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Name: "EvalGraphBuilder",
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}).Build(path)
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}
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// See GraphBuilder
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func (b *EvalGraphBuilder) Steps() []GraphTransformer {
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concreteProvider := func(a *NodeAbstractProvider) dag.Vertex {
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return &NodeEvalableProvider{
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NodeAbstractProvider: a,
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}
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}
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steps := []GraphTransformer{
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// Creates all the data resources that aren't in the state. This will also
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// add any orphans from scaling in as destroy nodes.
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&ConfigTransformer{
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Concrete: nil, // just use the abstract type
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Config: b.Config,
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Unique: true,
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},
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// Attach the state
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&AttachStateTransformer{State: b.State},
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// Attach the configuration to any resources
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&AttachResourceConfigTransformer{Config: b.Config},
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// Add root variables
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&RootVariableTransformer{Config: b.Config},
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TransformProviders(b.Components.ResourceProviders(), concreteProvider, b.Config),
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// Add the local values
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&LocalTransformer{Config: b.Config},
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// Add the outputs
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&OutputTransformer{Config: b.Config},
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// Add module variables
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&ModuleVariableTransformer{Config: b.Config},
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// Must be before ReferenceTransformer, since schema is required to
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// extract references from config.
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&AttachSchemaTransformer{Components: b.Components},
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// Connect so that the references are ready for targeting. We'll
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// have to connect again later for providers and so on.
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&ReferenceTransformer{},
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// Although we don't configure providers, we do still start them up
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// to get their schemas, and so we must shut them down again here.
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&CloseProviderTransformer{},
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// Single root
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&RootTransformer{},
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// Remove redundant edges to simplify the graph.
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&TransitiveReductionTransformer{},
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}
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return steps
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}
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