hcl/parser: Support lists of objects

a.k.a lists of maps

Implementation was pretty straightforward - I had to tweak the `needsComma`
handling since it was stuck inside literal parsing. It happens out front
now. I also promoted the `assign_deep.hcl` parser test to a decoder
test that passes, since it was testing for an error to occur but now it
works! :)

Additionally we make ObjectLists support being comma-delimited, which
enables maps to defined inline like `{one = 1, two = 2}`.

Refs https://github.com/hashicorp/terraform/issues/7142

decoder_test.go

@@ -194,6 +194,27 @@ func TestDecode_interface(t *testing.T) {
 				},
 			},
 		},
+		{
+			"list_of_maps.hcl",
+			false,
+			map[string]interface{}{
+				"foo": []interface{}{
+					map[string]interface{}{"somekey1": "someval1"},
+					map[string]interface{}{"somekey2": "someval2", "someextrakey": "someextraval"},
+				},
+			},
+		},
+		{
+			"assign_deep.hcl",
+			false,
+			map[string]interface{}{
+				"resource": []interface{}{
+					map[string]interface{}{
+						"foo": []interface{}{
+							map[string]interface{}{
+								"bar": []map[string]interface{}{
+									map[string]interface{}{}}}}}}},
+		},
 		{
 			"structure_list.hcl",
 			false,

hcl/parser/parser.go

@@ -79,6 +79,13 @@ func (p *Parser) objectList() (*ast.ObjectList, error) {
 		}
 
 		node.Add(n)
+
+		// object lists can be optionally comma-delimited e.g. when a list of maps
+		// is being expressed, so a comma is allowed here - it's simply consumed
+		tok := p.scan()
+		if tok.Type != token.COMMA {
+			p.unscan()
+		}
 	}
 	return node, nil
 }
@@ -311,15 +318,20 @@ func (p *Parser) listType() (*ast.ListType, error) {
 	needComma := false
 	for {
 		tok := p.scan()
-		switch tok.Type {
-		case token.NUMBER, token.FLOAT, token.STRING, token.HEREDOC:
-			if needComma {
+		if needComma {
+			switch tok.Type {
+			case token.COMMA, token.RBRACK:
+			default:
 				return nil, &PosError{
 					Pos: tok.Pos,
-					Err: fmt.Errorf("unexpected token: %s. Expecting %s", tok.Type, token.COMMA),
+					Err: fmt.Errorf(
+						"error parsing list, expected comma or list end, got: %s",
+						tok.Type),
 				}
 			}
-
+		}
+		switch tok.Type {
+		case token.NUMBER, token.FLOAT, token.STRING, token.HEREDOC:
 			node, err := p.literalType()
 			if err != nil {
 				return nil, err
@@ -343,6 +355,18 @@ func (p *Parser) listType() (*ast.ListType, error) {
 
 			needComma = false
 			continue
+		case token.LBRACE:
+			// Looks like a nested object, so parse it out
+			node, err := p.objectType()
+			if err != nil {
+				return nil, &PosError{
+					Pos: tok.Pos,
+					Err: fmt.Errorf(
+						"error while trying to parse object within list: %s", err),
+				}
+			}
+			l.Add(node)
+			needComma = true
 		case token.BOOL:
 			// TODO(arslan) should we support? not supported by HCL yet
 		case token.LBRACK:

hcl/parser/parser_test.go

@@ -6,6 +6,7 @@ import (
 	"path/filepath"
 	"reflect"
 	"runtime"
+	"strings"
 	"testing"
 
 	"github.com/hashicorp/hcl/hcl/ast"
@@ -99,6 +100,58 @@ EOF
 	}
 }
 
+func TestListOfMaps(t *testing.T) {
+	src := `foo = [
+    {key = "bar"},
+    {key = "baz", key2 = "qux"},
+  ]`
+	p := newParser([]byte(src))
+
+	file, err := p.Parse()
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	// Here we make all sorts of assumptions about the input structure w/ type
+	// assertions. The intent is only for this to be a "smoke test" ensuring
+	// parsing actually performed its duty - giving this test something a bit
+	// more robust than _just_ "no error occurred".
+	expected := []string{`"bar"`, `"baz"`, `"qux"`}
+	actual := make([]string, 0, 3)
+	ol := file.Node.(*ast.ObjectList)
+	objItem := ol.Items[0]
+	list := objItem.Val.(*ast.ListType)
+	for _, node := range list.List {
+		obj := node.(*ast.ObjectType)
+		for _, item := range obj.List.Items {
+			val := item.Val.(*ast.LiteralType)
+			actual = append(actual, val.Token.Text)
+		}
+
+	}
+	if !reflect.DeepEqual(expected, actual) {
+		t.Fatalf("Expected: %#v, got %#v", expected, actual)
+	}
+}
+
+func TestListOfMaps_requiresComma(t *testing.T) {
+	src := `foo = [
+    {key = "bar"}
+    {key = "baz"}
+  ]`
+	p := newParser([]byte(src))
+
+	_, err := p.Parse()
+	if err == nil {
+		t.Fatalf("Expected error, got none!")
+	}
+
+	expected := "error parsing list, expected comma or list end"
+	if !strings.Contains(err.Error(), expected) {
+		t.Fatalf("Expected err:\n  %s\nTo contain:\n  %s\n", err, expected)
+	}
+}
+
 func TestObjectType(t *testing.T) {
 	var literals = []struct {
 		src      string
@@ -263,6 +316,10 @@ func TestParse(t *testing.T) {
 			"multiple.hcl",
 			false,
 		},
+		{
+			"object_list_comma.hcl",
+			false,
+		},
 		{
 			"structure.hcl",
 			false,
@@ -279,10 +336,6 @@ func TestParse(t *testing.T) {
 			"complex.hcl",
 			false,
 		},
-		{
-			"assign_deep.hcl",
-			true,
-		},
 		{
 			"types.hcl",
 			false,

hcl/parser/test-fixtures/object_list_comma.hcl

@@ -0,0 +1 @@
+foo = {one = 1, two = 2}

test-fixtures/list_of_maps.hcl

@@ -0,0 +1,4 @@
+foo = [
+  {somekey1 = "someval1"},
+  {somekey2 = "someval2", someextrakey = "someextraval"},
+]