MinItems and MaxItems can be validated once again

The new hcldec dynamic block behavior no longer tried to validate
MinItems and MaxItems when the number of values is unknown.

configs/configschema/decoder_spec.go

@@ -101,15 +101,6 @@ func (b *Block) DecoderSpec() hcldec.Spec {
 
 		childSpec := blockS.Block.DecoderSpec()
 
-		// We can only validate 0 or 1 for MinItems, because a dynamic block
-		// may satisfy any number of min items while only having a single
-		// block in the config. We cannot validate MaxItems because a
-		// configuration may have any number of dynamic blocks.
-		minItems := 0
-		if blockS.MinItems > 1 {
-			minItems = 1
-		}
-
 		switch blockS.Nesting {
 		case NestingSingle, NestingGroup:
 			ret[name] = &hcldec.BlockSpec{
@@ -134,13 +125,15 @@ func (b *Block) DecoderSpec() hcldec.Spec {
 				ret[name] = &hcldec.BlockTupleSpec{
 					TypeName: name,
 					Nested:   childSpec,
-					MinItems: minItems,
+					MinItems: blockS.MinItems,
+					MaxItems: blockS.MaxItems,
 				}
 			} else {
 				ret[name] = &hcldec.BlockListSpec{
 					TypeName: name,
 					Nested:   childSpec,
-					MinItems: minItems,
+					MinItems: blockS.MinItems,
+					MaxItems: blockS.MaxItems,
 				}
 			}
 		case NestingSet:
@@ -154,7 +147,8 @@ func (b *Block) DecoderSpec() hcldec.Spec {
 			ret[name] = &hcldec.BlockSetSpec{
 				TypeName: name,
 				Nested:   childSpec,
-				MinItems: minItems,
+				MinItems: blockS.MinItems,
+				MaxItems: blockS.MaxItems,
 			}
 		case NestingMap:
 			// We prefer to use a list where possible, since it makes our

configs/configschema/decoder_spec_test.go

@@ -344,15 +344,12 @@ func TestBlockDecoderSpec(t *testing.T) {
 					},
 					&hcl.Block{
 						Type: "foo",
-						Body: hcl.EmptyBody(),
+						Body: unknownBody{hcl.EmptyBody()},
 					},
 				},
 			}),
 			cty.ObjectVal(map[string]cty.Value{
-				"foo": cty.ListVal([]cty.Value{
-					cty.EmptyObjectVal,
-					cty.EmptyObjectVal,
-				}),
+				"foo": cty.UnknownVal(cty.List(cty.EmptyObject)),
 			}),
 			0, // max items cannot be validated during decode
 		},
@@ -372,14 +369,12 @@ func TestBlockDecoderSpec(t *testing.T) {
 				Blocks: hcl.Blocks{
 					&hcl.Block{
 						Type: "foo",
-						Body: hcl.EmptyBody(),
+						Body: unknownBody{hcl.EmptyBody()},
 					},
 				},
 			}),
 			cty.ObjectVal(map[string]cty.Value{
-				"foo": cty.ListVal([]cty.Value{
-					cty.EmptyObjectVal,
-				}),
+				"foo": cty.UnknownVal(cty.List(cty.EmptyObject)),
 			}),
 			0,
 		},
@@ -401,6 +396,7 @@ func TestBlockDecoderSpec(t *testing.T) {
 	for name, test := range tests {
 		t.Run(name, func(t *testing.T) {
 			spec := test.Schema.DecoderSpec()
+
 			got, diags := hcldec.Decode(test.TestBody, spec, nil)
 			if len(diags) != test.DiagCount {
 				t.Errorf("wrong number of diagnostics %d; want %d", len(diags), test.DiagCount)
@@ -427,6 +423,16 @@ func TestBlockDecoderSpec(t *testing.T) {
 	}
 }
 
+// this satisfies hcldec.UnknownBody to simulate a dynamic block with an
+// unknown number of values.
+type unknownBody struct {
+	hcl.Body
+}
+
+func (b unknownBody) Unknown() bool {
+	return true
+}
+
 func TestAttributeDecoderSpec(t *testing.T) {
 	tests := map[string]struct {
 		Schema    *Attribute