Expander.ExpandResource

It turns out that within terraform resource expansion will normally
happen with an absolute address. This is because in order to evaluate
the expansion expression, we need to already have the context within a
module instance.

This leaves the existing ExpandResource logic in place as
ExpandModuleResource since it's working, and in case we do find a
location where it's useful to get a full expansion (which may be needed
for instance dependency tracking)

Reword some of the resource related arguments and comments, as they were
copied from the module methods and not entirely accurate.

instances/expander.go

@@ -70,26 +70,26 @@ func (e *Expander) SetModuleForEach(parentAddr addrs.ModuleInstance, callAddr ad
 	e.setModuleExpansion(parentAddr, callAddr, expansionForEach(mapping))
 }
 
-// SetResourceSingle records that the given module inside the given parent
+// SetResourceSingle records that the given resource inside the given module
-// module does not use any repetition arguments and is therefore a singleton.
+// does not use any repetition arguments and is therefore a singleton.
-func (e *Expander) SetResourceSingle(parentAddr addrs.ModuleInstance, resourceAddr addrs.Resource) {
+func (e *Expander) SetResourceSingle(moduleAddr addrs.ModuleInstance, resourceAddr addrs.Resource) {
-	e.setResourceExpansion(parentAddr, resourceAddr, expansionSingleVal)
+	e.setResourceExpansion(moduleAddr, resourceAddr, expansionSingleVal)
 }
 
-// SetResourceCount records that the given module inside the given parent
+// SetResourceCount records that the given resource inside the given module
-// module uses the "count" repetition argument, with the given value.
+// uses the "count" repetition argument, with the given value.
-func (e *Expander) SetResourceCount(parentAddr addrs.ModuleInstance, resourceAddr addrs.Resource, count int) {
+func (e *Expander) SetResourceCount(moduleAddr addrs.ModuleInstance, resourceAddr addrs.Resource, count int) {
-	e.setResourceExpansion(parentAddr, resourceAddr, expansionCount(count))
+	e.setResourceExpansion(moduleAddr, resourceAddr, expansionCount(count))
 }
 
-// SetResourceForEach records that the given module inside the given parent
+// SetResourceForEach records that the given resource inside the given module
-// module uses the "for_each" repetition argument, with the given map value.
+// uses the "for_each" repetition argument, with the given map value.
 //
 // In the configuration language the for_each argument can also accept a set.
 // It's the caller's responsibility to convert that into an identity map before
 // calling this method.
-func (e *Expander) SetResourceForEach(parentAddr addrs.ModuleInstance, resourceAddr addrs.Resource, mapping map[string]cty.Value) {
+func (e *Expander) SetResourceForEach(moduleAddr addrs.ModuleInstance, resourceAddr addrs.Resource, mapping map[string]cty.Value) {
-	e.setResourceExpansion(parentAddr, resourceAddr, expansionForEach(mapping))
+	e.setResourceExpansion(moduleAddr, resourceAddr, expansionForEach(mapping))
 }
 
 // ExpandModule finds the exhaustive set of module instances resulting from
@@ -120,13 +120,13 @@ func (e *Expander) ExpandModule(addr addrs.Module) []addrs.ModuleInstance {
 	return ret
 }
 
-// ExpandResource finds the exhaustive set of resource instances resulting from
+// ExpandModuleResource finds the exhaustive set of resource instances resulting from
 // the expansion of the given resource and all of its containing modules.
 //
 // All of the modules on the path to the identified resource and the resource
 // itself must already have had their expansion registered using one of the
 // SetModule*/SetResource* methods before calling, or this method will panic.
-func (e *Expander) ExpandResource(parentAddr addrs.Module, resourceAddr addrs.Resource) []addrs.AbsResourceInstance {
+func (e *Expander) ExpandModuleResource(moduleAddr addrs.Module, resourceAddr addrs.Resource) []addrs.AbsResourceInstance {
 	e.mu.RLock()
 	defer e.mu.RUnlock()
 
@@ -136,13 +136,33 @@ func (e *Expander) ExpandResource(parentAddr addrs.Module, resourceAddr addrs.Re
 	// (moduleInstances does plenty of allocations itself, so the benefit of
 	// pre-allocating this is marginal but it's not hard to do.)
 	moduleInstanceAddr := make(addrs.ModuleInstance, 0, 4)
-	ret := e.exps.resourceInstances(parentAddr, resourceAddr, moduleInstanceAddr)
+	ret := e.exps.resourceInstances(moduleAddr, resourceAddr, moduleInstanceAddr)
 	sort.SliceStable(ret, func(i, j int) bool {
 		return ret[i].Less(ret[j])
 	})
 	return ret
 }
 
+// ExpandResource finds the set of resource instances resulting from
+// the expansion of the given resource within its module instance.
+//
+// All of the modules on the path to the identified resource and the resource
+// itself must already have had their expansion registered using one of the
+// SetModule*/SetResource* methods before calling, or this method will panic.
+func (e *Expander) ExpandResource(resourceAddr addrs.AbsResource) []addrs.AbsResourceInstance {
+	var ret []addrs.AbsResourceInstance
+
+	// Take the full set of expanded resource instances and filter for only
+	// those within our module instance.
+	for _, r := range e.ExpandModuleResource(resourceAddr.Module.Module(), resourceAddr.Resource) {
+		if !r.Module.Equal(resourceAddr.Module) {
+			continue
+		}
+		ret = append(ret, r)
+	}
+	return ret
+}
+
 // GetModuleInstanceRepetitionData returns an object describing the values
 // that should be available for each.key, each.value, and count.index within
 // the call block for the given module instance.

instances/expander_test.go

@@ -130,7 +130,7 @@ func TestExpander(t *testing.T) {
 		}
 	})
 	t.Run("resource single", func(t *testing.T) {
-		got := ex.ExpandResource(
+		got := ex.ExpandModuleResource(
 			addrs.RootModule,
 			singleResourceAddr,
 		)
@@ -142,7 +142,7 @@ func TestExpander(t *testing.T) {
 		}
 	})
 	t.Run("resource count2", func(t *testing.T) {
-		got := ex.ExpandResource(
+		got := ex.ExpandModuleResource(
 			addrs.RootModule,
 			count2ResourceAddr,
 		)
@@ -155,7 +155,7 @@ func TestExpander(t *testing.T) {
 		}
 	})
 	t.Run("resource count0", func(t *testing.T) {
-		got := ex.ExpandResource(
+		got := ex.ExpandModuleResource(
 			addrs.RootModule,
 			count0ResourceAddr,
 		)
@@ -165,7 +165,7 @@ func TestExpander(t *testing.T) {
 		}
 	})
 	t.Run("resource for_each", func(t *testing.T) {
-		got := ex.ExpandResource(
+		got := ex.ExpandModuleResource(
 			addrs.RootModule,
 			forEachResourceAddr,
 		)
@@ -187,7 +187,7 @@ func TestExpander(t *testing.T) {
 		}
 	})
 	t.Run("module single resource single", func(t *testing.T) {
-		got := ex.ExpandResource(
+		got := ex.ExpandModuleResource(
 			mustModuleAddr("single"),
 			singleResourceAddr,
 		)
@@ -199,7 +199,7 @@ func TestExpander(t *testing.T) {
 		}
 	})
 	t.Run("module single resource count2", func(t *testing.T) {
-		got := ex.ExpandResource(
+		got := ex.ExpandModuleResource(
 			mustModuleAddr(`single`),
 			count2ResourceAddr,
 		)
@@ -222,7 +222,7 @@ func TestExpander(t *testing.T) {
 		}
 	})
 	t.Run("module count2 resource single", func(t *testing.T) {
-		got := ex.ExpandResource(
+		got := ex.ExpandModuleResource(
 			mustModuleAddr(`count2`),
 			singleResourceAddr,
 		)
@@ -235,7 +235,7 @@ func TestExpander(t *testing.T) {
 		}
 	})
 	t.Run("module count2 resource count2", func(t *testing.T) {
-		got := ex.ExpandResource(
+		got := ex.ExpandModuleResource(
 			mustModuleAddr(`count2`),
 			count2ResourceAddr,
 		)
@@ -262,7 +262,7 @@ func TestExpander(t *testing.T) {
 		}
 	})
 	t.Run("module count2 resource count2 resource count2", func(t *testing.T) {
-		got := ex.ExpandResource(
+		got := ex.ExpandModuleResource(
 			mustModuleAddr(`count2.count2`),
 			count2ResourceAddr,
 		)
@@ -280,6 +280,18 @@ func TestExpander(t *testing.T) {
 			t.Errorf("wrong result\n%s", diff)
 		}
 	})
+	t.Run("module count2 resource count2 resource count2", func(t *testing.T) {
+		got := ex.ExpandResource(
+			count2ResourceAddr.Absolute(mustModuleInstanceAddr(`module.count2[0].module.count2[1]`)),
+		)
+		want := []addrs.AbsResourceInstance{
+			mustAbsResourceInstanceAddr(`module.count2[0].module.count2[1].test.count2[0]`),
+			mustAbsResourceInstanceAddr(`module.count2[0].module.count2[1].test.count2[1]`),
+		}
+		if diff := cmp.Diff(want, got); diff != "" {
+			t.Errorf("wrong result\n%s", diff)
+		}
+	})
 	t.Run("module count0", func(t *testing.T) {
 		got := ex.ExpandModule(mustModuleAddr(`count0`))
 		want := []addrs.ModuleInstance(nil)
@@ -288,7 +300,7 @@ func TestExpander(t *testing.T) {
 		}
 	})
 	t.Run("module count0 resource single", func(t *testing.T) {
-		got := ex.ExpandResource(
+		got := ex.ExpandModuleResource(
 			mustModuleAddr(`count0`),
 			singleResourceAddr,
 		)
@@ -311,7 +323,7 @@ func TestExpander(t *testing.T) {
 		}
 	})
 	t.Run("module for_each resource single", func(t *testing.T) {
-		got := ex.ExpandResource(
+		got := ex.ExpandModuleResource(
 			mustModuleAddr(`for_each`),
 			singleResourceAddr,
 		)
@@ -324,7 +336,7 @@ func TestExpander(t *testing.T) {
 		}
 	})
 	t.Run("module for_each resource count2", func(t *testing.T) {
-		got := ex.ExpandResource(
+		got := ex.ExpandModuleResource(
 			mustModuleAddr(`for_each`),
 			count2ResourceAddr,
 		)
@@ -338,6 +350,18 @@ func TestExpander(t *testing.T) {
 			t.Errorf("wrong result\n%s", diff)
 		}
 	})
+	t.Run("module for_each resource count2", func(t *testing.T) {
+		got := ex.ExpandResource(
+			count2ResourceAddr.Absolute(mustModuleInstanceAddr(`module.for_each["a"]`)),
+		)
+		want := []addrs.AbsResourceInstance{
+			mustAbsResourceInstanceAddr(`module.for_each["a"].test.count2[0]`),
+			mustAbsResourceInstanceAddr(`module.for_each["a"].test.count2[1]`),
+		}
+		if diff := cmp.Diff(want, got); diff != "" {
+			t.Errorf("wrong result\n%s", diff)
+		}
+	})
 
 	t.Run(`module.for_each["b"] repetitiondata`, func(t *testing.T) {
 		got := ex.GetModuleInstanceRepetitionData(