testharness: "resource" context constructor

The result of calling this can be passed into the first argument of
"describe" to create a description with a resource as context. In child
blocks it can also be used to access the attributes of a resource selected
by a parent block.

testharness/context_setters.go

@@ -42,7 +42,7 @@ type resourceContextSetter struct {
 	DefRange tfdiags.SourceRange
 }
 
-func (s resourceContextSetter) Context(parent *Context, subject *Subject) (*Context, tfdiags.Diagnostics) {
+func (s *resourceContextSetter) Context(parent *Context, subject *Subject) (*Context, tfdiags.Diagnostics) {
 	// TODO: Set the resource object too
 	return parent.WithNameSuffix(s.Addr.String()), nil
 }

testharness/loader.go

@@ -140,10 +140,12 @@ func loadSpec(r io.Reader, filename string, L *lua.LState) (*Spec, tfdiags.Diagn
 		Diags: builderDiags,
 	}
 	testersB := testersBuilder{
-		Diags: builderDiags,
+		Context: RootContext,
+		Diags:   builderDiags,
 	}
 	topEnv.RawSet(lua.LString("scenario"), L.NewFunction(scenariosB.luaScenarioFunc))
 	topEnv.RawSet(lua.LString("describe"), L.NewFunction(testersB.luaDescribeFunc))
+	topEnv.RawSet(lua.LString("resource"), testersB.luaResourceObj(L))
 
 	L.Push(fn)
 	err = L.PCall(0, 0, nil)

testharness/loader_test.go

@@ -61,7 +61,7 @@ func TestLoadSpecDir(t *testing.T) {
 	}
 
 	{
-		if got, want := len(spec.testers), 1; got != want {
+		if got, want := len(spec.testers), 2; got != want {
 			t.Fatalf("wrong number of testers %d; want %d", got, want)
 		}
 
@@ -77,5 +77,18 @@ func TestLoadSpecDir(t *testing.T) {
 		} else {
 			t.Errorf("spec.testers[0] is %T; want *describe", spec.testers[0])
 		}
+
+		resourceTester := spec.testers[1]
+		if resourceTester, isResource := resourceTester.(*describe); isResource {
+			if resourceCtxSet, isResource := resourceTester.Described.(*resourceContextSetter); isResource {
+				if got, want := resourceCtxSet.Addr.String(), "test.foo"; got != want {
+					t.Errorf("spec.testers[1] has wrong resource address %q; want %q", got, want)
+				}
+			} else {
+				t.Errorf("spec.testers[1].Described is %T; want resourceContextSetter", resourceTester.Described)
+			}
+		} else {
+			t.Errorf("spec.testers[1] is %T; want *describe", spec.testers[0])
+		}
 	}
 }

testharness/test-fixtures/basic-specs/b.tfspec

@@ -6,3 +6,7 @@ end)
 describe("foo", function ()
 
 end)
+
+describe(resource("test.foo"), function ()
+
+end)

testharness/testers_builder.go

@@ -1,14 +1,19 @@
 package testharness
 
 import (
+	"fmt"
+
 	"github.com/hashicorp/hcl2/hcl"
+	"github.com/hashicorp/terraform/terraform"
 	"github.com/hashicorp/terraform/tfdiags"
 	lua "github.com/yuin/gopher-lua"
+	"github.com/zclconf/gopherlua-cty/luacty"
 )
 
 // testersBuilder provides functions for constructing a sequence of testers
 // from within a Lua test spec.
 type testersBuilder struct {
+	Context *Context
 	Testers Testers
 	Diags   *Diagnostics
 }
@@ -71,3 +76,51 @@ func (b *testersBuilder) luaDescribeFunc(L *lua.LState) int {
 
 	return 0
 }
+
+func (b *testersBuilder) luaResourceObj(L *lua.LState) lua.LValue {
+	ret := L.NewUserData()
+	meta := L.NewTable()
+
+	conv := luacty.NewConverter(L)
+
+	if b.Context.HasResource() {
+		meta.RawSet(lua.LString("__index"), conv.WrapCtyValue(b.Context.Resource()))
+		meta.RawSet(lua.LString("__call"), L.NewFunction(func(L *lua.LState) int {
+			L.Error(lua.LString("a resource is already being described by a parent block"), 2)
+			return 0
+		}))
+	} else {
+		meta.RawSet(lua.LString("__index"), L.NewFunction(func(L *lua.LState) int {
+			L.Error(lua.LString("no resource is being described by the current block"), 2)
+			return 0
+		}))
+		meta.RawSet(lua.LString("__call"), L.NewFunction(func(L *lua.LState) int {
+			addrS := L.CheckString(2)
+			addr, err := terraform.ParseResourceAddress(addrS)
+			if err != nil {
+				L.Error(lua.LString(fmt.Sprintf("invalid resource address: %s", err)), 2)
+				return 0
+			}
+			if addr.Name == "" {
+				L.Error(lua.LString("invalid resource address: must refer to specific resource"), 2)
+				return 0
+			}
+
+			ctxSet := &resourceContextSetter{
+				Addr: addr,
+			}
+			if rng := callingRange(L, 1); rng != nil {
+				ctxSet.DefRange = tfdiags.SourceRangeFromHCL(*rng)
+			}
+
+			ret := L.NewUserData()
+			ret.Value = ctxSet
+			L.Push(ret)
+			return 1
+		}))
+	}
+
+	ret.Metatable = meta
+
+	return ret
+}