github.com/adrian-bl/terraform@v0.7.0-rc2.0.20160705220747-de0a34fc3517/terraform/transform_resource.go (about)

     1  package terraform
     2  
     3  import (
     4  	"fmt"
     5  	"strings"
     6  
     7  	"github.com/hashicorp/terraform/config"
     8  	"github.com/hashicorp/terraform/dag"
     9  )
    10  
    11  // ResourceCountTransformer is a GraphTransformer that expands the count
    12  // out for a specific resource.
    13  type ResourceCountTransformer struct {
    14  	Resource *config.Resource
    15  	Destroy  bool
    16  	Targets  []ResourceAddress
    17  }
    18  
    19  func (t *ResourceCountTransformer) Transform(g *Graph) error {
    20  	// Expand the resource count
    21  	count, err := t.Resource.Count()
    22  	if err != nil {
    23  		return err
    24  	}
    25  
    26  	// Don't allow the count to be negative
    27  	if count < 0 {
    28  		return fmt.Errorf("negative count: %d", count)
    29  	}
    30  
    31  	// For each count, build and add the node
    32  	nodes := make([]dag.Vertex, 0, count)
    33  	for i := 0; i < count; i++ {
    34  		// Set the index. If our count is 1 we special case it so that
    35  		// we handle the "resource.0" and "resource" boundary properly.
    36  		index := i
    37  		if count == 1 {
    38  			index = -1
    39  		}
    40  
    41  		// Save the node for later so we can do connections. Make the
    42  		// proper node depending on if we're just a destroy node or if
    43  		// were a regular node.
    44  		var node dag.Vertex = &graphNodeExpandedResource{
    45  			Index:    index,
    46  			Resource: t.Resource,
    47  			Path:     g.Path,
    48  		}
    49  		if t.Destroy {
    50  			node = &graphNodeExpandedResourceDestroy{
    51  				graphNodeExpandedResource: node.(*graphNodeExpandedResource),
    52  			}
    53  		}
    54  
    55  		// Skip nodes if targeting excludes them
    56  		if !t.nodeIsTargeted(node) {
    57  			continue
    58  		}
    59  
    60  		// Add the node now
    61  		nodes = append(nodes, node)
    62  		g.Add(node)
    63  	}
    64  
    65  	// Make the dependency connections
    66  	for _, n := range nodes {
    67  		// Connect the dependents. We ignore the return value for missing
    68  		// dependents since that should've been caught at a higher level.
    69  		g.ConnectDependent(n)
    70  	}
    71  
    72  	return nil
    73  }
    74  
    75  func (t *ResourceCountTransformer) nodeIsTargeted(node dag.Vertex) bool {
    76  	// no targets specified, everything stays in the graph
    77  	if len(t.Targets) == 0 {
    78  		return true
    79  	}
    80  	addressable, ok := node.(GraphNodeAddressable)
    81  	if !ok {
    82  		return false
    83  	}
    84  
    85  	addr := addressable.ResourceAddress()
    86  	for _, targetAddr := range t.Targets {
    87  		if targetAddr.Equals(addr) {
    88  			return true
    89  		}
    90  	}
    91  	return false
    92  }
    93  
    94  type graphNodeExpandedResource struct {
    95  	Index    int
    96  	Resource *config.Resource
    97  	Path     []string
    98  }
    99  
   100  func (n *graphNodeExpandedResource) Name() string {
   101  	if n.Index == -1 {
   102  		return n.Resource.Id()
   103  	}
   104  
   105  	return fmt.Sprintf("%s #%d", n.Resource.Id(), n.Index)
   106  }
   107  
   108  // GraphNodeAddressable impl.
   109  func (n *graphNodeExpandedResource) ResourceAddress() *ResourceAddress {
   110  	// We want this to report the logical index properly, so we must undo the
   111  	// special case from the expand
   112  	index := n.Index
   113  	if index == -1 {
   114  		index = 0
   115  	}
   116  	return &ResourceAddress{
   117  		Path:         n.Path[1:],
   118  		Index:        index,
   119  		InstanceType: TypePrimary,
   120  		Name:         n.Resource.Name,
   121  		Type:         n.Resource.Type,
   122  		Mode:         n.Resource.Mode,
   123  	}
   124  }
   125  
   126  // graphNodeConfig impl.
   127  func (n *graphNodeExpandedResource) ConfigType() GraphNodeConfigType {
   128  	return GraphNodeConfigTypeResource
   129  }
   130  
   131  // GraphNodeDependable impl.
   132  func (n *graphNodeExpandedResource) DependableName() []string {
   133  	return []string{
   134  		n.Resource.Id(),
   135  		n.stateId(),
   136  	}
   137  }
   138  
   139  // GraphNodeDependent impl.
   140  func (n *graphNodeExpandedResource) DependentOn() []string {
   141  	configNode := &GraphNodeConfigResource{Resource: n.Resource}
   142  	result := configNode.DependentOn()
   143  
   144  	// Walk the variables to find any count-specific variables we depend on.
   145  	configNode.VarWalk(func(v config.InterpolatedVariable) {
   146  		rv, ok := v.(*config.ResourceVariable)
   147  		if !ok {
   148  			return
   149  		}
   150  
   151  		// We only want ourselves
   152  		if rv.ResourceId() != n.Resource.Id() {
   153  			return
   154  		}
   155  
   156  		// If this isn't a multi-access (which shouldn't be allowed but
   157  		// is verified elsewhere), then we depend on the specific count
   158  		// of this resource, ignoring ourself (which again should be
   159  		// validated elsewhere).
   160  		if rv.Index > -1 {
   161  			id := fmt.Sprintf("%s.%d", rv.ResourceId(), rv.Index)
   162  			if id != n.stateId() && id != n.stateId()+".0" {
   163  				result = append(result, id)
   164  			}
   165  		}
   166  	})
   167  
   168  	return result
   169  }
   170  
   171  // GraphNodeProviderConsumer
   172  func (n *graphNodeExpandedResource) ProvidedBy() []string {
   173  	return []string{resourceProvider(n.Resource.Type, n.Resource.Provider)}
   174  }
   175  
   176  func (n *graphNodeExpandedResource) StateDependencies() []string {
   177  	depsRaw := n.DependentOn()
   178  	deps := make([]string, 0, len(depsRaw))
   179  	for _, d := range depsRaw {
   180  		// Ignore any variable dependencies
   181  		if strings.HasPrefix(d, "var.") {
   182  			continue
   183  		}
   184  
   185  		// This is sad. The dependencies are currently in the format of
   186  		// "module.foo.bar" (the full field). This strips the field off.
   187  		if strings.HasPrefix(d, "module.") {
   188  			parts := strings.SplitN(d, ".", 3)
   189  			d = strings.Join(parts[0:2], ".")
   190  		}
   191  		deps = append(deps, d)
   192  	}
   193  
   194  	return deps
   195  }
   196  
   197  // GraphNodeEvalable impl.
   198  func (n *graphNodeExpandedResource) EvalTree() EvalNode {
   199  	var provider ResourceProvider
   200  	var resourceConfig *ResourceConfig
   201  
   202  	// Build the resource. If we aren't part of a multi-resource, then
   203  	// we still consider ourselves as count index zero.
   204  	index := n.Index
   205  	if index < 0 {
   206  		index = 0
   207  	}
   208  	resource := &Resource{
   209  		Name:       n.Resource.Name,
   210  		Type:       n.Resource.Type,
   211  		CountIndex: index,
   212  	}
   213  
   214  	seq := &EvalSequence{Nodes: make([]EvalNode, 0, 5)}
   215  
   216  	// Validate the resource
   217  	vseq := &EvalSequence{Nodes: make([]EvalNode, 0, 5)}
   218  	vseq.Nodes = append(vseq.Nodes, &EvalGetProvider{
   219  		Name:   n.ProvidedBy()[0],
   220  		Output: &provider,
   221  	})
   222  	vseq.Nodes = append(vseq.Nodes, &EvalInterpolate{
   223  		Config:   n.Resource.RawConfig.Copy(),
   224  		Resource: resource,
   225  		Output:   &resourceConfig,
   226  	})
   227  	vseq.Nodes = append(vseq.Nodes, &EvalValidateResource{
   228  		Provider:     &provider,
   229  		Config:       &resourceConfig,
   230  		ResourceName: n.Resource.Name,
   231  		ResourceType: n.Resource.Type,
   232  		ResourceMode: n.Resource.Mode,
   233  	})
   234  
   235  	// Validate all the provisioners
   236  	for _, p := range n.Resource.Provisioners {
   237  		var provisioner ResourceProvisioner
   238  		vseq.Nodes = append(vseq.Nodes, &EvalGetProvisioner{
   239  			Name:   p.Type,
   240  			Output: &provisioner,
   241  		}, &EvalInterpolate{
   242  			Config:   p.RawConfig.Copy(),
   243  			Resource: resource,
   244  			Output:   &resourceConfig,
   245  		}, &EvalValidateProvisioner{
   246  			Provisioner: &provisioner,
   247  			Config:      &resourceConfig,
   248  		})
   249  	}
   250  
   251  	// Add the validation operations
   252  	seq.Nodes = append(seq.Nodes, &EvalOpFilter{
   253  		Ops:  []walkOperation{walkValidate},
   254  		Node: vseq,
   255  	})
   256  
   257  	// Build instance info
   258  	info := n.instanceInfo()
   259  	seq.Nodes = append(seq.Nodes, &EvalInstanceInfo{Info: info})
   260  
   261  	// Each resource mode has its own lifecycle
   262  	switch n.Resource.Mode {
   263  	case config.ManagedResourceMode:
   264  		seq.Nodes = append(
   265  			seq.Nodes,
   266  			n.managedResourceEvalNodes(resource, info, resourceConfig)...,
   267  		)
   268  	case config.DataResourceMode:
   269  		seq.Nodes = append(
   270  			seq.Nodes,
   271  			n.dataResourceEvalNodes(resource, info, resourceConfig)...,
   272  		)
   273  	default:
   274  		panic(fmt.Errorf("unsupported resource mode %s", n.Resource.Mode))
   275  	}
   276  
   277  	return seq
   278  }
   279  
   280  func (n *graphNodeExpandedResource) managedResourceEvalNodes(resource *Resource, info *InstanceInfo, resourceConfig *ResourceConfig) []EvalNode {
   281  	var diff *InstanceDiff
   282  	var provider ResourceProvider
   283  	var state *InstanceState
   284  
   285  	nodes := make([]EvalNode, 0, 5)
   286  
   287  	// Refresh the resource
   288  	nodes = append(nodes, &EvalOpFilter{
   289  		Ops: []walkOperation{walkRefresh},
   290  		Node: &EvalSequence{
   291  			Nodes: []EvalNode{
   292  				&EvalGetProvider{
   293  					Name:   n.ProvidedBy()[0],
   294  					Output: &provider,
   295  				},
   296  				&EvalReadState{
   297  					Name:   n.stateId(),
   298  					Output: &state,
   299  				},
   300  				&EvalRefresh{
   301  					Info:     info,
   302  					Provider: &provider,
   303  					State:    &state,
   304  					Output:   &state,
   305  				},
   306  				&EvalWriteState{
   307  					Name:         n.stateId(),
   308  					ResourceType: n.Resource.Type,
   309  					Provider:     n.Resource.Provider,
   310  					Dependencies: n.StateDependencies(),
   311  					State:        &state,
   312  				},
   313  			},
   314  		},
   315  	})
   316  
   317  	// Diff the resource
   318  	nodes = append(nodes, &EvalOpFilter{
   319  		Ops: []walkOperation{walkPlan},
   320  		Node: &EvalSequence{
   321  			Nodes: []EvalNode{
   322  				&EvalInterpolate{
   323  					Config:   n.Resource.RawConfig.Copy(),
   324  					Resource: resource,
   325  					Output:   &resourceConfig,
   326  				},
   327  				&EvalGetProvider{
   328  					Name:   n.ProvidedBy()[0],
   329  					Output: &provider,
   330  				},
   331  				// Re-run validation to catch any errors we missed, e.g. type
   332  				// mismatches on computed values.
   333  				&EvalValidateResource{
   334  					Provider:       &provider,
   335  					Config:         &resourceConfig,
   336  					ResourceName:   n.Resource.Name,
   337  					ResourceType:   n.Resource.Type,
   338  					ResourceMode:   n.Resource.Mode,
   339  					IgnoreWarnings: true,
   340  				},
   341  				&EvalReadState{
   342  					Name:   n.stateId(),
   343  					Output: &state,
   344  				},
   345  				&EvalDiff{
   346  					Info:        info,
   347  					Config:      &resourceConfig,
   348  					Provider:    &provider,
   349  					State:       &state,
   350  					OutputDiff:  &diff,
   351  					OutputState: &state,
   352  				},
   353  				&EvalCheckPreventDestroy{
   354  					Resource: n.Resource,
   355  					Diff:     &diff,
   356  				},
   357  				&EvalIgnoreChanges{
   358  					Resource: n.Resource,
   359  					Diff:     &diff,
   360  				},
   361  				&EvalWriteState{
   362  					Name:         n.stateId(),
   363  					ResourceType: n.Resource.Type,
   364  					Provider:     n.Resource.Provider,
   365  					Dependencies: n.StateDependencies(),
   366  					State:        &state,
   367  				},
   368  				&EvalWriteDiff{
   369  					Name: n.stateId(),
   370  					Diff: &diff,
   371  				},
   372  			},
   373  		},
   374  	})
   375  
   376  	// Diff the resource for destruction
   377  	nodes = append(nodes, &EvalOpFilter{
   378  		Ops: []walkOperation{walkPlanDestroy},
   379  		Node: &EvalSequence{
   380  			Nodes: []EvalNode{
   381  				&EvalReadState{
   382  					Name:   n.stateId(),
   383  					Output: &state,
   384  				},
   385  				&EvalDiffDestroy{
   386  					Info:   info,
   387  					State:  &state,
   388  					Output: &diff,
   389  				},
   390  				&EvalCheckPreventDestroy{
   391  					Resource: n.Resource,
   392  					Diff:     &diff,
   393  				},
   394  				&EvalWriteDiff{
   395  					Name: n.stateId(),
   396  					Diff: &diff,
   397  				},
   398  			},
   399  		},
   400  	})
   401  
   402  	// Apply
   403  	var diffApply *InstanceDiff
   404  	var err error
   405  	var createNew bool
   406  	var createBeforeDestroyEnabled bool
   407  	var wasChangeType DiffChangeType
   408  	nodes = append(nodes, &EvalOpFilter{
   409  		Ops: []walkOperation{walkApply, walkDestroy},
   410  		Node: &EvalSequence{
   411  			Nodes: []EvalNode{
   412  				// Get the saved diff for apply
   413  				&EvalReadDiff{
   414  					Name: n.stateId(),
   415  					Diff: &diffApply,
   416  				},
   417  
   418  				// We don't want to do any destroys
   419  				&EvalIf{
   420  					If: func(ctx EvalContext) (bool, error) {
   421  						if diffApply == nil {
   422  							return true, EvalEarlyExitError{}
   423  						}
   424  
   425  						if diffApply.Destroy && len(diffApply.Attributes) == 0 {
   426  							return true, EvalEarlyExitError{}
   427  						}
   428  
   429  						wasChangeType = diffApply.ChangeType()
   430  						diffApply.Destroy = false
   431  						return true, nil
   432  					},
   433  					Then: EvalNoop{},
   434  				},
   435  
   436  				&EvalIf{
   437  					If: func(ctx EvalContext) (bool, error) {
   438  						destroy := false
   439  						if diffApply != nil {
   440  							destroy = diffApply.Destroy || diffApply.RequiresNew()
   441  						}
   442  
   443  						createBeforeDestroyEnabled =
   444  							n.Resource.Lifecycle.CreateBeforeDestroy &&
   445  								destroy
   446  
   447  						return createBeforeDestroyEnabled, nil
   448  					},
   449  					Then: &EvalDeposeState{
   450  						Name: n.stateId(),
   451  					},
   452  				},
   453  
   454  				&EvalInterpolate{
   455  					Config:   n.Resource.RawConfig.Copy(),
   456  					Resource: resource,
   457  					Output:   &resourceConfig,
   458  				},
   459  				&EvalGetProvider{
   460  					Name:   n.ProvidedBy()[0],
   461  					Output: &provider,
   462  				},
   463  				&EvalReadState{
   464  					Name:   n.stateId(),
   465  					Output: &state,
   466  				},
   467  				// Re-run validation to catch any errors we missed, e.g. type
   468  				// mismatches on computed values.
   469  				&EvalValidateResource{
   470  					Provider:       &provider,
   471  					Config:         &resourceConfig,
   472  					ResourceName:   n.Resource.Name,
   473  					ResourceType:   n.Resource.Type,
   474  					ResourceMode:   n.Resource.Mode,
   475  					IgnoreWarnings: true,
   476  				},
   477  				&EvalDiff{
   478  					Info:       info,
   479  					Config:     &resourceConfig,
   480  					Provider:   &provider,
   481  					Diff:       &diffApply,
   482  					State:      &state,
   483  					OutputDiff: &diffApply,
   484  				},
   485  				&EvalIgnoreChanges{
   486  					Resource:      n.Resource,
   487  					Diff:          &diffApply,
   488  					WasChangeType: &wasChangeType,
   489  				},
   490  
   491  				// Get the saved diff
   492  				&EvalReadDiff{
   493  					Name: n.stateId(),
   494  					Diff: &diff,
   495  				},
   496  
   497  				// Compare the diffs
   498  				&EvalCompareDiff{
   499  					Info: info,
   500  					One:  &diff,
   501  					Two:  &diffApply,
   502  				},
   503  
   504  				&EvalGetProvider{
   505  					Name:   n.ProvidedBy()[0],
   506  					Output: &provider,
   507  				},
   508  				&EvalReadState{
   509  					Name:   n.stateId(),
   510  					Output: &state,
   511  				},
   512  				&EvalApply{
   513  					Info:      info,
   514  					State:     &state,
   515  					Diff:      &diffApply,
   516  					Provider:  &provider,
   517  					Output:    &state,
   518  					Error:     &err,
   519  					CreateNew: &createNew,
   520  				},
   521  				&EvalWriteState{
   522  					Name:         n.stateId(),
   523  					ResourceType: n.Resource.Type,
   524  					Provider:     n.Resource.Provider,
   525  					Dependencies: n.StateDependencies(),
   526  					State:        &state,
   527  				},
   528  				&EvalApplyProvisioners{
   529  					Info:           info,
   530  					State:          &state,
   531  					Resource:       n.Resource,
   532  					InterpResource: resource,
   533  					CreateNew:      &createNew,
   534  					Error:          &err,
   535  				},
   536  				&EvalIf{
   537  					If: func(ctx EvalContext) (bool, error) {
   538  						return createBeforeDestroyEnabled && err != nil, nil
   539  					},
   540  					Then: &EvalUndeposeState{
   541  						Name:  n.stateId(),
   542  						State: &state,
   543  					},
   544  					Else: &EvalWriteState{
   545  						Name:         n.stateId(),
   546  						ResourceType: n.Resource.Type,
   547  						Provider:     n.Resource.Provider,
   548  						Dependencies: n.StateDependencies(),
   549  						State:        &state,
   550  					},
   551  				},
   552  
   553  				// We clear the diff out here so that future nodes
   554  				// don't see a diff that is already complete. There
   555  				// is no longer a diff!
   556  				&EvalWriteDiff{
   557  					Name: n.stateId(),
   558  					Diff: nil,
   559  				},
   560  
   561  				&EvalApplyPost{
   562  					Info:  info,
   563  					State: &state,
   564  					Error: &err,
   565  				},
   566  				&EvalUpdateStateHook{},
   567  			},
   568  		},
   569  	})
   570  
   571  	return nodes
   572  }
   573  
   574  func (n *graphNodeExpandedResource) dataResourceEvalNodes(resource *Resource, info *InstanceInfo, resourceConfig *ResourceConfig) []EvalNode {
   575  	//var diff *InstanceDiff
   576  	var provider ResourceProvider
   577  	var config *ResourceConfig
   578  	var diff *InstanceDiff
   579  	var state *InstanceState
   580  
   581  	nodes := make([]EvalNode, 0, 5)
   582  
   583  	// Refresh the resource
   584  	nodes = append(nodes, &EvalOpFilter{
   585  		Ops: []walkOperation{walkRefresh},
   586  		Node: &EvalSequence{
   587  			Nodes: []EvalNode{
   588  
   589  				// Always destroy the existing state first, since we must
   590  				// make sure that values from a previous read will not
   591  				// get interpolated if we end up needing to defer our
   592  				// loading until apply time.
   593  				&EvalWriteState{
   594  					Name:         n.stateId(),
   595  					ResourceType: n.Resource.Type,
   596  					Provider:     n.Resource.Provider,
   597  					Dependencies: n.StateDependencies(),
   598  					State:        &state, // state is nil here
   599  				},
   600  
   601  				&EvalInterpolate{
   602  					Config:   n.Resource.RawConfig.Copy(),
   603  					Resource: resource,
   604  					Output:   &config,
   605  				},
   606  
   607  				// The rest of this pass can proceed only if there are no
   608  				// computed values in our config.
   609  				// (If there are, we'll deal with this during the plan and
   610  				// apply phases.)
   611  				&EvalIf{
   612  					If: func(ctx EvalContext) (bool, error) {
   613  						if config.ComputedKeys != nil && len(config.ComputedKeys) > 0 {
   614  							return true, EvalEarlyExitError{}
   615  						}
   616  
   617  						return true, nil
   618  					},
   619  					Then: EvalNoop{},
   620  				},
   621  
   622  				// The remainder of this pass is the same as running
   623  				// a "plan" pass immediately followed by an "apply" pass,
   624  				// populating the state early so it'll be available to
   625  				// provider configurations that need this data during
   626  				// refresh/plan.
   627  
   628  				&EvalGetProvider{
   629  					Name:   n.ProvidedBy()[0],
   630  					Output: &provider,
   631  				},
   632  
   633  				&EvalReadDataDiff{
   634  					Info:        info,
   635  					Config:      &config,
   636  					Provider:    &provider,
   637  					Output:      &diff,
   638  					OutputState: &state,
   639  				},
   640  
   641  				&EvalReadDataApply{
   642  					Info:     info,
   643  					Diff:     &diff,
   644  					Provider: &provider,
   645  					Output:   &state,
   646  				},
   647  
   648  				&EvalWriteState{
   649  					Name:         n.stateId(),
   650  					ResourceType: n.Resource.Type,
   651  					Provider:     n.Resource.Provider,
   652  					Dependencies: n.StateDependencies(),
   653  					State:        &state,
   654  				},
   655  
   656  				&EvalUpdateStateHook{},
   657  			},
   658  		},
   659  	})
   660  
   661  	// Diff the resource
   662  	nodes = append(nodes, &EvalOpFilter{
   663  		Ops: []walkOperation{walkPlan},
   664  		Node: &EvalSequence{
   665  			Nodes: []EvalNode{
   666  
   667  				&EvalReadState{
   668  					Name:   n.stateId(),
   669  					Output: &state,
   670  				},
   671  
   672  				// We need to re-interpolate the config here because some
   673  				// of the attributes may have become computed during
   674  				// earlier planning, due to other resources having
   675  				// "requires new resource" diffs.
   676  				&EvalInterpolate{
   677  					Config:   n.Resource.RawConfig.Copy(),
   678  					Resource: resource,
   679  					Output:   &config,
   680  				},
   681  
   682  				&EvalIf{
   683  					If: func(ctx EvalContext) (bool, error) {
   684  						computed := config.ComputedKeys != nil && len(config.ComputedKeys) > 0
   685  
   686  						// If the configuration is complete and we
   687  						// already have a state then we don't need to
   688  						// do any further work during apply, because we
   689  						// already populated the state during refresh.
   690  						if !computed && state != nil {
   691  							return true, EvalEarlyExitError{}
   692  						}
   693  
   694  						return true, nil
   695  					},
   696  					Then: EvalNoop{},
   697  				},
   698  
   699  				&EvalGetProvider{
   700  					Name:   n.ProvidedBy()[0],
   701  					Output: &provider,
   702  				},
   703  
   704  				&EvalReadDataDiff{
   705  					Info:        info,
   706  					Config:      &config,
   707  					Provider:    &provider,
   708  					Output:      &diff,
   709  					OutputState: &state,
   710  				},
   711  
   712  				&EvalWriteState{
   713  					Name:         n.stateId(),
   714  					ResourceType: n.Resource.Type,
   715  					Provider:     n.Resource.Provider,
   716  					Dependencies: n.StateDependencies(),
   717  					State:        &state,
   718  				},
   719  
   720  				&EvalWriteDiff{
   721  					Name: n.stateId(),
   722  					Diff: &diff,
   723  				},
   724  			},
   725  		},
   726  	})
   727  
   728  	// Diff the resource for destruction
   729  	nodes = append(nodes, &EvalOpFilter{
   730  		Ops: []walkOperation{walkPlanDestroy},
   731  		Node: &EvalSequence{
   732  			Nodes: []EvalNode{
   733  
   734  				&EvalReadState{
   735  					Name:   n.stateId(),
   736  					Output: &state,
   737  				},
   738  
   739  				// Since EvalDiffDestroy doesn't interact with the
   740  				// provider at all, we can safely share the same
   741  				// implementation for data vs. managed resources.
   742  				&EvalDiffDestroy{
   743  					Info:   info,
   744  					State:  &state,
   745  					Output: &diff,
   746  				},
   747  
   748  				&EvalWriteDiff{
   749  					Name: n.stateId(),
   750  					Diff: &diff,
   751  				},
   752  			},
   753  		},
   754  	})
   755  
   756  	// Apply
   757  	nodes = append(nodes, &EvalOpFilter{
   758  		Ops: []walkOperation{walkApply, walkDestroy},
   759  		Node: &EvalSequence{
   760  			Nodes: []EvalNode{
   761  				// Get the saved diff for apply
   762  				&EvalReadDiff{
   763  					Name: n.stateId(),
   764  					Diff: &diff,
   765  				},
   766  
   767  				// Stop here if we don't actually have a diff
   768  				&EvalIf{
   769  					If: func(ctx EvalContext) (bool, error) {
   770  						if diff == nil {
   771  							return true, EvalEarlyExitError{}
   772  						}
   773  
   774  						if len(diff.Attributes) == 0 {
   775  							return true, EvalEarlyExitError{}
   776  						}
   777  
   778  						return true, nil
   779  					},
   780  					Then: EvalNoop{},
   781  				},
   782  
   783  				// We need to re-interpolate the config here, rather than
   784  				// just using the diff's values directly, because we've
   785  				// potentially learned more variable values during the
   786  				// apply pass that weren't known when the diff was produced.
   787  				&EvalInterpolate{
   788  					Config:   n.Resource.RawConfig.Copy(),
   789  					Resource: resource,
   790  					Output:   &config,
   791  				},
   792  
   793  				&EvalGetProvider{
   794  					Name:   n.ProvidedBy()[0],
   795  					Output: &provider,
   796  				},
   797  
   798  				// Make a new diff with our newly-interpolated config.
   799  				&EvalReadDataDiff{
   800  					Info:     info,
   801  					Config:   &config,
   802  					Previous: &diff,
   803  					Provider: &provider,
   804  					Output:   &diff,
   805  				},
   806  
   807  				&EvalReadDataApply{
   808  					Info:     info,
   809  					Diff:     &diff,
   810  					Provider: &provider,
   811  					Output:   &state,
   812  				},
   813  
   814  				&EvalWriteState{
   815  					Name:         n.stateId(),
   816  					ResourceType: n.Resource.Type,
   817  					Provider:     n.Resource.Provider,
   818  					Dependencies: n.StateDependencies(),
   819  					State:        &state,
   820  				},
   821  
   822  				// Clear the diff now that we've applied it, so
   823  				// later nodes won't see a diff that's now a no-op.
   824  				&EvalWriteDiff{
   825  					Name: n.stateId(),
   826  					Diff: nil,
   827  				},
   828  
   829  				&EvalUpdateStateHook{},
   830  			},
   831  		},
   832  	})
   833  
   834  	return nodes
   835  }
   836  
   837  // instanceInfo is used for EvalTree.
   838  func (n *graphNodeExpandedResource) instanceInfo() *InstanceInfo {
   839  	return &InstanceInfo{Id: n.stateId(), Type: n.Resource.Type}
   840  }
   841  
   842  // stateId is the name used for the state key
   843  func (n *graphNodeExpandedResource) stateId() string {
   844  	if n.Index == -1 {
   845  		return n.Resource.Id()
   846  	}
   847  
   848  	return fmt.Sprintf("%s.%d", n.Resource.Id(), n.Index)
   849  }
   850  
   851  // GraphNodeStateRepresentative impl.
   852  func (n *graphNodeExpandedResource) StateId() []string {
   853  	return []string{n.stateId()}
   854  }
   855  
   856  // graphNodeExpandedResourceDestroy represents an expanded resource that
   857  // is to be destroyed.
   858  type graphNodeExpandedResourceDestroy struct {
   859  	*graphNodeExpandedResource
   860  }
   861  
   862  func (n *graphNodeExpandedResourceDestroy) Name() string {
   863  	return fmt.Sprintf("%s (destroy)", n.graphNodeExpandedResource.Name())
   864  }
   865  
   866  // graphNodeConfig impl.
   867  func (n *graphNodeExpandedResourceDestroy) ConfigType() GraphNodeConfigType {
   868  	return GraphNodeConfigTypeResource
   869  }
   870  
   871  // GraphNodeEvalable impl.
   872  func (n *graphNodeExpandedResourceDestroy) EvalTree() EvalNode {
   873  	info := n.instanceInfo()
   874  
   875  	var diffApply *InstanceDiff
   876  	var provider ResourceProvider
   877  	var state *InstanceState
   878  	var err error
   879  	return &EvalOpFilter{
   880  		Ops: []walkOperation{walkApply, walkDestroy},
   881  		Node: &EvalSequence{
   882  			Nodes: []EvalNode{
   883  				// Get the saved diff for apply
   884  				&EvalReadDiff{
   885  					Name: n.stateId(),
   886  					Diff: &diffApply,
   887  				},
   888  
   889  				// Filter the diff so we only get the destroy
   890  				&EvalFilterDiff{
   891  					Diff:    &diffApply,
   892  					Output:  &diffApply,
   893  					Destroy: true,
   894  				},
   895  
   896  				// If we're not destroying, then compare diffs
   897  				&EvalIf{
   898  					If: func(ctx EvalContext) (bool, error) {
   899  						if diffApply != nil && diffApply.Destroy {
   900  							return true, nil
   901  						}
   902  
   903  						return true, EvalEarlyExitError{}
   904  					},
   905  					Then: EvalNoop{},
   906  				},
   907  
   908  				&EvalGetProvider{
   909  					Name:   n.ProvidedBy()[0],
   910  					Output: &provider,
   911  				},
   912  				&EvalReadState{
   913  					Name:   n.stateId(),
   914  					Output: &state,
   915  				},
   916  				&EvalRequireState{
   917  					State: &state,
   918  				},
   919  				// Make sure we handle data sources properly.
   920  				&EvalIf{
   921  					If: func(ctx EvalContext) (bool, error) {
   922  						if n.Resource.Mode == config.DataResourceMode {
   923  							return true, nil
   924  						}
   925  
   926  						return false, nil
   927  					},
   928  
   929  					Then: &EvalReadDataApply{
   930  						Info:     info,
   931  						Diff:     &diffApply,
   932  						Provider: &provider,
   933  						Output:   &state,
   934  					},
   935  					Else: &EvalApply{
   936  						Info:     info,
   937  						State:    &state,
   938  						Diff:     &diffApply,
   939  						Provider: &provider,
   940  						Output:   &state,
   941  						Error:    &err,
   942  					},
   943  				},
   944  				&EvalWriteState{
   945  					Name:         n.stateId(),
   946  					ResourceType: n.Resource.Type,
   947  					Provider:     n.Resource.Provider,
   948  					Dependencies: n.StateDependencies(),
   949  					State:        &state,
   950  				},
   951  				&EvalApplyPost{
   952  					Info:  info,
   953  					State: &state,
   954  					Error: &err,
   955  				},
   956  			},
   957  		},
   958  	}
   959  }