vendor/github.com/hashicorp/terraform/terraform/interpolate.go

   1 package terraform
   2
   3 import (
   4         "fmt"
   5         "log"
   6         "os"
   7         "strconv"
   8         "strings"
   9         "sync"
  10
  11         "github.com/hashicorp/hil"
  12         "github.com/hashicorp/hil/ast"
  13         "github.com/hashicorp/terraform/config"
  14         "github.com/hashicorp/terraform/config/module"
  15         "github.com/hashicorp/terraform/flatmap"
  16 )
  17
  18 const (
  19         // VarEnvPrefix is the prefix of variables that are read from
  20         // the environment to set variables here.
  21         VarEnvPrefix = "TF_VAR_"
  22 )
  23
  24 // Interpolater is the structure responsible for determining the values
  25 // for interpolations such as `aws_instance.foo.bar`.
  26 type Interpolater struct {
  27         Operation          walkOperation
  28         Meta               *ContextMeta
  29         Module             *module.Tree
  30         State              *State
  31         StateLock          *sync.RWMutex
  32         VariableValues     map[string]interface{}
  33         VariableValuesLock *sync.Mutex
  34 }
  35
  36 // InterpolationScope is the current scope of execution. This is required
  37 // since some variables which are interpolated are dependent on what we're
  38 // operating on and where we are.
  39 type InterpolationScope struct {
  40         Path     []string
  41         Resource *Resource
  42 }
  43
  44 // Values returns the values for all the variables in the given map.
  45 func (i *Interpolater) Values(
  46         scope *InterpolationScope,
  47         vars map[string]config.InterpolatedVariable) (map[string]ast.Variable, error) {
  48         if scope == nil {
  49                 scope = &InterpolationScope{}
  50         }
  51
  52         result := make(map[string]ast.Variable, len(vars))
  53
  54         // Copy the default variables
  55         if i.Module != nil && scope != nil {
  56                 mod := i.Module
  57                 if len(scope.Path) > 1 {
  58                         mod = i.Module.Child(scope.Path[1:])
  59                 }
  60                 for _, v := range mod.Config().Variables {
  61                         // Set default variables
  62                         if v.Default == nil {
  63                                 continue
  64                         }
  65
  66                         n := fmt.Sprintf("var.%s", v.Name)
  67                         variable, err := hil.InterfaceToVariable(v.Default)
  68                         if err != nil {
  69                                 return nil, fmt.Errorf("invalid default map value for %s: %v", v.Name, v.Default)
  70                         }
  71
  72                         result[n] = variable
  73                 }
  74         }
  75
  76         for n, rawV := range vars {
  77                 var err error
  78                 switch v := rawV.(type) {
  79                 case *config.CountVariable:
  80                         err = i.valueCountVar(scope, n, v, result)
  81                 case *config.ModuleVariable:
  82                         err = i.valueModuleVar(scope, n, v, result)
  83                 case *config.PathVariable:
  84                         err = i.valuePathVar(scope, n, v, result)
  85                 case *config.ResourceVariable:
  86                         err = i.valueResourceVar(scope, n, v, result)
  87                 case *config.SelfVariable:
  88                         err = i.valueSelfVar(scope, n, v, result)
  89                 case *config.SimpleVariable:
  90                         err = i.valueSimpleVar(scope, n, v, result)
  91                 case *config.TerraformVariable:
  92                         err = i.valueTerraformVar(scope, n, v, result)
  93                 case *config.UserVariable:
  94                         err = i.valueUserVar(scope, n, v, result)
  95                 default:
  96                         err = fmt.Errorf("%s: unknown variable type: %T", n, rawV)
  97                 }
  98
  99                 if err != nil {
 100                         return nil, err
 101                 }
 102         }
 103
 104         return result, nil
 105 }
 106
 107 func (i *Interpolater) valueCountVar(
 108         scope *InterpolationScope,
 109         n string,
 110         v *config.CountVariable,
 111         result map[string]ast.Variable) error {
 112         switch v.Type {
 113         case config.CountValueIndex:
 114                 if scope.Resource == nil {
 115                         return fmt.Errorf("%s: count.index is only valid within resources", n)
 116                 }
 117                 result[n] = ast.Variable{
 118                         Value: scope.Resource.CountIndex,
 119                         Type:  ast.TypeInt,
 120                 }
 121                 return nil
 122         default:
 123                 return fmt.Errorf("%s: unknown count type: %#v", n, v.Type)
 124         }
 125 }
 126
 127 func unknownVariable() ast.Variable {
 128         return ast.Variable{
 129                 Type:  ast.TypeUnknown,
 130                 Value: config.UnknownVariableValue,
 131         }
 132 }
 133
 134 func unknownValue() string {
 135         return hil.UnknownValue
 136 }
 137
 138 func (i *Interpolater) valueModuleVar(
 139         scope *InterpolationScope,
 140         n string,
 141         v *config.ModuleVariable,
 142         result map[string]ast.Variable) error {
 143
 144         // Build the path to the child module we want
 145         path := make([]string, len(scope.Path), len(scope.Path)+1)
 146         copy(path, scope.Path)
 147         path = append(path, v.Name)
 148
 149         // Grab the lock so that if other interpolations are running or
 150         // state is being modified, we'll be safe.
 151         i.StateLock.RLock()
 152         defer i.StateLock.RUnlock()
 153
 154         // Get the module where we're looking for the value
 155         mod := i.State.ModuleByPath(path)
 156         if mod == nil {
 157                 // If the module doesn't exist, then we can return an empty string.
 158                 // This happens usually only in Refresh() when we haven't populated
 159                 // a state. During validation, we semantically verify that all
 160                 // modules reference other modules, and graph ordering should
 161                 // ensure that the module is in the state, so if we reach this
 162                 // point otherwise it really is a panic.
 163                 result[n] = unknownVariable()
 164
 165                 // During apply this is always an error
 166                 if i.Operation == walkApply {
 167                         return fmt.Errorf(
 168                                 "Couldn't find module %q for var: %s",
 169                                 v.Name, v.FullKey())
 170                 }
 171         } else {
 172                 // Get the value from the outputs
 173                 if outputState, ok := mod.Outputs[v.Field]; ok {
 174                         output, err := hil.InterfaceToVariable(outputState.Value)
 175                         if err != nil {
 176                                 return err
 177                         }
 178                         result[n] = output
 179                 } else {
 180                         // Same reasons as the comment above.
 181                         result[n] = unknownVariable()
 182
 183                         // During apply this is always an error
 184                         if i.Operation == walkApply {
 185                                 return fmt.Errorf(
 186                                         "Couldn't find output %q for module var: %s",
 187                                         v.Field, v.FullKey())
 188                         }
 189                 }
 190         }
 191
 192         return nil
 193 }
 194
 195 func (i *Interpolater) valuePathVar(
 196         scope *InterpolationScope,
 197         n string,
 198         v *config.PathVariable,
 199         result map[string]ast.Variable) error {
 200         switch v.Type {
 201         case config.PathValueCwd:
 202                 wd, err := os.Getwd()
 203                 if err != nil {
 204                         return fmt.Errorf(
 205                                 "Couldn't get cwd for var %s: %s",
 206                                 v.FullKey(), err)
 207                 }
 208
 209                 result[n] = ast.Variable{
 210                         Value: wd,
 211                         Type:  ast.TypeString,
 212                 }
 213         case config.PathValueModule:
 214                 if t := i.Module.Child(scope.Path[1:]); t != nil {
 215                         result[n] = ast.Variable{
 216                                 Value: t.Config().Dir,
 217                                 Type:  ast.TypeString,
 218                         }
 219                 }
 220         case config.PathValueRoot:
 221                 result[n] = ast.Variable{
 222                         Value: i.Module.Config().Dir,
 223                         Type:  ast.TypeString,
 224                 }
 225         default:
 226                 return fmt.Errorf("%s: unknown path type: %#v", n, v.Type)
 227         }
 228
 229         return nil
 230
 231 }
 232
 233 func (i *Interpolater) valueResourceVar(
 234         scope *InterpolationScope,
 235         n string,
 236         v *config.ResourceVariable,
 237         result map[string]ast.Variable) error {
 238         // If we're computing all dynamic fields, then module vars count
 239         // and we mark it as computed.
 240         if i.Operation == walkValidate {
 241                 result[n] = unknownVariable()
 242                 return nil
 243         }
 244
 245         var variable *ast.Variable
 246         var err error
 247
 248         if v.Multi && v.Index == -1 {
 249                 variable, err = i.computeResourceMultiVariable(scope, v)
 250         } else {
 251                 variable, err = i.computeResourceVariable(scope, v)
 252         }
 253
 254         if err != nil {
 255                 return err
 256         }
 257
 258         if variable == nil {
 259                 // During the input walk we tolerate missing variables because
 260                 // we haven't yet had a chance to refresh state, so dynamic data may
 261                 // not yet be complete.
 262                 // If it truly is missing, we'll catch it on a later walk.
 263                 // This applies only to graph nodes that interpolate during the
 264                 // config walk, e.g. providers.
 265                 if i.Operation == walkInput || i.Operation == walkRefresh {
 266                         result[n] = unknownVariable()
 267                         return nil
 268                 }
 269
 270                 return fmt.Errorf("variable %q is nil, but no error was reported", v.Name)
 271         }
 272
 273         result[n] = *variable
 274         return nil
 275 }
 276
 277 func (i *Interpolater) valueSelfVar(
 278         scope *InterpolationScope,
 279         n string,
 280         v *config.SelfVariable,
 281         result map[string]ast.Variable) error {
 282         if scope == nil || scope.Resource == nil {
 283                 return fmt.Errorf(
 284                         "%s: invalid scope, self variables are only valid on resources", n)
 285         }
 286
 287         rv, err := config.NewResourceVariable(fmt.Sprintf(
 288                 "%s.%s.%d.%s",
 289                 scope.Resource.Type,
 290                 scope.Resource.Name,
 291                 scope.Resource.CountIndex,
 292                 v.Field))
 293         if err != nil {
 294                 return err
 295         }
 296
 297         return i.valueResourceVar(scope, n, rv, result)
 298 }
 299
 300 func (i *Interpolater) valueSimpleVar(
 301         scope *InterpolationScope,
 302         n string,
 303         v *config.SimpleVariable,
 304         result map[string]ast.Variable) error {
 305         // This error message includes some information for people who
 306         // relied on this for their template_file data sources. We should
 307         // remove this at some point but there isn't any rush.
 308         return fmt.Errorf(
 309                 "invalid variable syntax: %q. Did you mean 'var.%s'? If this is part of inline `template` parameter\n"+
 310                         "then you must escape the interpolation with two dollar signs. For\n"+
 311                         "example: ${a} becomes $${a}.",
 312                 n, n)
 313 }
 314
 315 func (i *Interpolater) valueTerraformVar(
 316         scope *InterpolationScope,
 317         n string,
 318         v *config.TerraformVariable,
 319         result map[string]ast.Variable) error {
 320         if v.Field != "env" {
 321                 return fmt.Errorf(
 322                         "%s: only supported key for 'terraform.X' interpolations is 'env'", n)
 323         }
 324
 325         if i.Meta == nil {
 326                 return fmt.Errorf(
 327                         "%s: internal error: nil Meta. Please report a bug.", n)
 328         }
 329
 330         result[n] = ast.Variable{Type: ast.TypeString, Value: i.Meta.Env}
 331         return nil
 332 }
 333
 334 func (i *Interpolater) valueUserVar(
 335         scope *InterpolationScope,
 336         n string,
 337         v *config.UserVariable,
 338         result map[string]ast.Variable) error {
 339         i.VariableValuesLock.Lock()
 340         defer i.VariableValuesLock.Unlock()
 341         val, ok := i.VariableValues[v.Name]
 342         if ok {
 343                 varValue, err := hil.InterfaceToVariable(val)
 344                 if err != nil {
 345                         return fmt.Errorf("cannot convert %s value %q to an ast.Variable for interpolation: %s",
 346                                 v.Name, val, err)
 347                 }
 348                 result[n] = varValue
 349                 return nil
 350         }
 351
 352         if _, ok := result[n]; !ok && i.Operation == walkValidate {
 353                 result[n] = unknownVariable()
 354                 return nil
 355         }
 356
 357         // Look up if we have any variables with this prefix because
 358         // those are map overrides. Include those.
 359         for k, val := range i.VariableValues {
 360                 if strings.HasPrefix(k, v.Name+".") {
 361                         keyComponents := strings.Split(k, ".")
 362                         overrideKey := keyComponents[len(keyComponents)-1]
 363
 364                         mapInterface, ok := result["var."+v.Name]
 365                         if !ok {
 366                                 return fmt.Errorf("override for non-existent variable: %s", v.Name)
 367                         }
 368
 369                         mapVariable := mapInterface.Value.(map[string]ast.Variable)
 370
 371                         varValue, err := hil.InterfaceToVariable(val)
 372                         if err != nil {
 373                                 return fmt.Errorf("cannot convert %s value %q to an ast.Variable for interpolation: %s",
 374                                         v.Name, val, err)
 375                         }
 376                         mapVariable[overrideKey] = varValue
 377                 }
 378         }
 379
 380         return nil
 381 }
 382
 383 func (i *Interpolater) computeResourceVariable(
 384         scope *InterpolationScope,
 385         v *config.ResourceVariable) (*ast.Variable, error) {
 386         id := v.ResourceId()
 387         if v.Multi {
 388                 id = fmt.Sprintf("%s.%d", id, v.Index)
 389         }
 390
 391         i.StateLock.RLock()
 392         defer i.StateLock.RUnlock()
 393
 394         unknownVariable := unknownVariable()
 395
 396         // These variables must be declared early because of the use of GOTO
 397         var isList bool
 398         var isMap bool
 399
 400         // Get the information about this resource variable, and verify
 401         // that it exists and such.
 402         module, cr, err := i.resourceVariableInfo(scope, v)
 403         if err != nil {
 404                 return nil, err
 405         }
 406
 407         // If we're requesting "count" its a special variable that we grab
 408         // directly from the config itself.
 409         if v.Field == "count" {
 410                 var count int
 411                 if cr != nil {
 412                         count, err = cr.Count()
 413                 } else {
 414                         count, err = i.resourceCountMax(module, cr, v)
 415                 }
 416                 if err != nil {
 417                         return nil, fmt.Errorf(
 418                                 "Error reading %s count: %s",
 419                                 v.ResourceId(),
 420                                 err)
 421                 }
 422
 423                 return &ast.Variable{Type: ast.TypeInt, Value: count}, nil
 424         }
 425
 426         // Get the resource out from the state. We know the state exists
 427         // at this point and if there is a state, we expect there to be a
 428         // resource with the given name.
 429         var r *ResourceState
 430         if module != nil && len(module.Resources) > 0 {
 431                 var ok bool
 432                 r, ok = module.Resources[id]
 433                 if !ok && v.Multi && v.Index == 0 {
 434                         r, ok = module.Resources[v.ResourceId()]
 435                 }
 436                 if !ok {
 437                         r = nil
 438                 }
 439         }
 440         if r == nil || r.Primary == nil {
 441                 if i.Operation == walkApply || i.Operation == walkPlan {
 442                         return nil, fmt.Errorf(
 443                                 "Resource '%s' not found for variable '%s'",
 444                                 v.ResourceId(),
 445                                 v.FullKey())
 446                 }
 447
 448                 // If we have no module in the state yet or count, return empty.
 449                 // NOTE(@mitchellh): I actually don't know why this is here. During
 450                 // a refactor I kept this here to maintain the same behavior, but
 451                 // I'm not sure why its here.
 452                 if module == nil || len(module.Resources) == 0 {
 453                         return nil, nil
 454                 }
 455
 456                 goto MISSING
 457         }
 458
 459         if attr, ok := r.Primary.Attributes[v.Field]; ok {
 460                 v, err := hil.InterfaceToVariable(attr)
 461                 return &v, err
 462         }
 463
 464         // computed list or map attribute
 465         _, isList = r.Primary.Attributes[v.Field+".#"]
 466         _, isMap = r.Primary.Attributes[v.Field+".%"]
 467         if isList || isMap {
 468                 variable, err := i.interpolateComplexTypeAttribute(v.Field, r.Primary.Attributes)
 469                 return &variable, err
 470         }
 471
 472         // At apply time, we can't do the "maybe has it" check below
 473         // that we need for plans since parent elements might be computed.
 474         // Therefore, it is an error and we're missing the key.
 475         //
 476         // TODO: test by creating a state and configuration that is referencing
 477         // a non-existent variable "foo.bar" where the state only has "foo"
 478         // and verify plan works, but apply doesn't.
 479         if i.Operation == walkApply || i.Operation == walkDestroy {
 480                 goto MISSING
 481         }
 482
 483         // We didn't find the exact field, so lets separate the dots
 484         // and see if anything along the way is a computed set. i.e. if
 485         // we have "foo.0.bar" as the field, check to see if "foo" is
 486         // a computed list. If so, then the whole thing is computed.
 487         if parts := strings.Split(v.Field, "."); len(parts) > 1 {
 488                 for i := 1; i < len(parts); i++ {
 489                         // Lists and sets make this
 490                         key := fmt.Sprintf("%s.#", strings.Join(parts[:i], "."))
 491                         if attr, ok := r.Primary.Attributes[key]; ok {
 492                                 v, err := hil.InterfaceToVariable(attr)
 493                                 return &v, err
 494                         }
 495
 496                         // Maps make this
 497                         key = fmt.Sprintf("%s", strings.Join(parts[:i], "."))
 498                         if attr, ok := r.Primary.Attributes[key]; ok {
 499                                 v, err := hil.InterfaceToVariable(attr)
 500                                 return &v, err
 501                         }
 502                 }
 503         }
 504
 505 MISSING:
 506         // Validation for missing interpolations should happen at a higher
 507         // semantic level. If we reached this point and don't have variables,
 508         // just return the computed value.
 509         if scope == nil && scope.Resource == nil {
 510                 return &unknownVariable, nil
 511         }
 512
 513         // If the operation is refresh, it isn't an error for a value to
 514         // be unknown. Instead, we return that the value is computed so
 515         // that the graph can continue to refresh other nodes. It doesn't
 516         // matter because the config isn't interpolated anyways.
 517         //
 518         // For a Destroy, we're also fine with computed values, since our goal is
 519         // only to get destroy nodes for existing resources.
 520         //
 521         // For an input walk, computed values are okay to return because we're only
 522         // looking for missing variables to prompt the user for.
 523         if i.Operation == walkRefresh || i.Operation == walkPlanDestroy || i.Operation == walkInput {
 524                 return &unknownVariable, nil
 525         }
 526
 527         return nil, fmt.Errorf(
 528                 "Resource '%s' does not have attribute '%s' "+
 529                         "for variable '%s'",
 530                 id,
 531                 v.Field,
 532                 v.FullKey())
 533 }
 534
 535 func (i *Interpolater) computeResourceMultiVariable(
 536         scope *InterpolationScope,
 537         v *config.ResourceVariable) (*ast.Variable, error) {
 538         i.StateLock.RLock()
 539         defer i.StateLock.RUnlock()
 540
 541         unknownVariable := unknownVariable()
 542
 543         // If we're only looking for input, we don't need to expand a
 544         // multi-variable. This prevents us from encountering things that should be
 545         // known but aren't because the state has yet to be refreshed.
 546         if i.Operation == walkInput {
 547                 return &unknownVariable, nil
 548         }
 549
 550         // Get the information about this resource variable, and verify
 551         // that it exists and such.
 552         module, cr, err := i.resourceVariableInfo(scope, v)
 553         if err != nil {
 554                 return nil, err
 555         }
 556
 557         // Get the keys for all the resources that are created for this resource
 558         countMax, err := i.resourceCountMax(module, cr, v)
 559         if err != nil {
 560                 return nil, err
 561         }
 562
 563         // If count is zero, we return an empty list
 564         if countMax == 0 {
 565                 return &ast.Variable{Type: ast.TypeList, Value: []ast.Variable{}}, nil
 566         }
 567
 568         // If we have no module in the state yet or count, return unknown
 569         if module == nil || len(module.Resources) == 0 {
 570                 return &unknownVariable, nil
 571         }
 572
 573         var values []interface{}
 574         for idx := 0; idx < countMax; idx++ {
 575                 id := fmt.Sprintf("%s.%d", v.ResourceId(), idx)
 576
 577                 // ID doesn't have a trailing index. We try both here, but if a value
 578                 // without a trailing index is found we prefer that. This choice
 579                 // is for legacy reasons: older versions of TF preferred it.
 580                 if id == v.ResourceId()+".0" {
 581                         potential := v.ResourceId()
 582                         if _, ok := module.Resources[potential]; ok {
 583                                 id = potential
 584                         }
 585                 }
 586
 587                 r, ok := module.Resources[id]
 588                 if !ok {
 589                         continue
 590                 }
 591
 592                 if r.Primary == nil {
 593                         continue
 594                 }
 595
 596                 if singleAttr, ok := r.Primary.Attributes[v.Field]; ok {
 597                         values = append(values, singleAttr)
 598                         continue
 599                 }
 600
 601                 // computed list or map attribute
 602                 _, isList := r.Primary.Attributes[v.Field+".#"]
 603                 _, isMap := r.Primary.Attributes[v.Field+".%"]
 604                 if !(isList || isMap) {
 605                         continue
 606                 }
 607                 multiAttr, err := i.interpolateComplexTypeAttribute(v.Field, r.Primary.Attributes)
 608                 if err != nil {
 609                         return nil, err
 610                 }
 611
 612                 values = append(values, multiAttr)
 613         }
 614
 615         if len(values) == 0 {
 616                 // If the operation is refresh, it isn't an error for a value to
 617                 // be unknown. Instead, we return that the value is computed so
 618                 // that the graph can continue to refresh other nodes. It doesn't
 619                 // matter because the config isn't interpolated anyways.
 620                 //
 621                 // For a Destroy, we're also fine with computed values, since our goal is
 622                 // only to get destroy nodes for existing resources.
 623                 //
 624                 // For an input walk, computed values are okay to return because we're only
 625                 // looking for missing variables to prompt the user for.
 626                 if i.Operation == walkRefresh || i.Operation == walkPlanDestroy || i.Operation == walkDestroy || i.Operation == walkInput {
 627                         return &unknownVariable, nil
 628                 }
 629
 630                 return nil, fmt.Errorf(
 631                         "Resource '%s' does not have attribute '%s' "+
 632                                 "for variable '%s'",
 633                         v.ResourceId(),
 634                         v.Field,
 635                         v.FullKey())
 636         }
 637
 638         variable, err := hil.InterfaceToVariable(values)
 639         return &variable, err
 640 }
 641
 642 func (i *Interpolater) interpolateComplexTypeAttribute(
 643         resourceID string,
 644         attributes map[string]string) (ast.Variable, error) {
 645
 646         // We can now distinguish between lists and maps in state by the count field:
 647         //    - lists (and by extension, sets) use the traditional .# notation
 648         //    - maps use the newer .% notation
 649         // Consequently here we can decide how to deal with the keys appropriately
 650         // based on whether the type is a map of list.
 651         if lengthAttr, isList := attributes[resourceID+".#"]; isList {
 652                 log.Printf("[DEBUG] Interpolating computed list element attribute %s (%s)",
 653                         resourceID, lengthAttr)
 654
 655                 // In Terraform's internal dotted representation of list-like attributes, the
 656                 // ".#" count field is marked as unknown to indicate "this whole list is
 657                 // unknown". We must honor that meaning here so computed references can be
 658                 // treated properly during the plan phase.
 659                 if lengthAttr == config.UnknownVariableValue {
 660                         return unknownVariable(), nil
 661                 }
 662
 663                 expanded := flatmap.Expand(attributes, resourceID)
 664                 return hil.InterfaceToVariable(expanded)
 665         }
 666
 667         if lengthAttr, isMap := attributes[resourceID+".%"]; isMap {
 668                 log.Printf("[DEBUG] Interpolating computed map element attribute %s (%s)",
 669                         resourceID, lengthAttr)
 670
 671                 // In Terraform's internal dotted representation of map attributes, the
 672                 // ".%" count field is marked as unknown to indicate "this whole list is
 673                 // unknown". We must honor that meaning here so computed references can be
 674                 // treated properly during the plan phase.
 675                 if lengthAttr == config.UnknownVariableValue {
 676                         return unknownVariable(), nil
 677                 }
 678
 679                 expanded := flatmap.Expand(attributes, resourceID)
 680                 return hil.InterfaceToVariable(expanded)
 681         }
 682
 683         return ast.Variable{}, fmt.Errorf("No complex type %s found", resourceID)
 684 }
 685
 686 func (i *Interpolater) resourceVariableInfo(
 687         scope *InterpolationScope,
 688         v *config.ResourceVariable) (*ModuleState, *config.Resource, error) {
 689         // Get the module tree that contains our current path. This is
 690         // either the current module (path is empty) or a child.
 691         modTree := i.Module
 692         if len(scope.Path) > 1 {
 693                 modTree = i.Module.Child(scope.Path[1:])
 694         }
 695
 696         // Get the resource from the configuration so we can verify
 697         // that the resource is in the configuration and so we can access
 698         // the configuration if we need to.
 699         var cr *config.Resource
 700         for _, r := range modTree.Config().Resources {
 701                 if r.Id() == v.ResourceId() {
 702                         cr = r
 703                         break
 704                 }
 705         }
 706
 707         // Get the relevant module
 708         module := i.State.ModuleByPath(scope.Path)
 709         return module, cr, nil
 710 }
 711
 712 func (i *Interpolater) resourceCountMax(
 713         ms *ModuleState,
 714         cr *config.Resource,
 715         v *config.ResourceVariable) (int, error) {
 716         id := v.ResourceId()
 717
 718         // If we're NOT applying, then we assume we can read the count
 719         // from the state. Plan and so on may not have any state yet so
 720         // we do a full interpolation.
 721         if i.Operation != walkApply {
 722                 if cr == nil {
 723                         return 0, nil
 724                 }
 725
 726                 count, err := cr.Count()
 727                 if err != nil {
 728                         return 0, err
 729                 }
 730
 731                 return count, nil
 732         }
 733
 734         // We need to determine the list of resource keys to get values from.
 735         // This needs to be sorted so the order is deterministic. We used to
 736         // use "cr.Count()" but that doesn't work if the count is interpolated
 737         // and we can't guarantee that so we instead depend on the state.
 738         max := -1
 739         for k, _ := range ms.Resources {
 740                 // Get the index number for this resource
 741                 index := ""
 742                 if k == id {
 743                         // If the key is the id, then its just 0 (no explicit index)
 744                         index = "0"
 745                 } else if strings.HasPrefix(k, id+".") {
 746                         // Grab the index number out of the state
 747                         index = k[len(id+"."):]
 748                         if idx := strings.IndexRune(index, '.'); idx >= 0 {
 749                                 index = index[:idx]
 750                         }
 751                 }
 752
 753                 // If there was no index then this resource didn't match
 754                 // the one we're looking for, exit.
 755                 if index == "" {
 756                         continue
 757                 }
 758
 759                 // Turn the index into an int
 760                 raw, err := strconv.ParseInt(index, 0, 0)
 761                 if err != nil {
 762                         return 0, fmt.Errorf(
 763                                 "%s: error parsing index %q as int: %s",
 764                                 id, index, err)
 765                 }
 766
 767                 // Keep track of this index if its the max
 768                 if new := int(raw); new > max {
 769                         max = new
 770                 }
 771         }
 772
 773         // If we never found any matching resources in the state, we
 774         // have zero.
 775         if max == -1 {
 776                 return 0, nil
 777         }
 778
 779         // The result value is "max+1" because we're returning the
 780         // max COUNT, not the max INDEX, and we zero-index.
 781         return max + 1, nil
 782 }