From 2bd7cfd5fe7b9e3cccbef8b96fd49f59e419cc7b Mon Sep 17 00:00:00 2001
From: James Bardin <j.bardin@gmail.com>
Date: Tue, 19 Jul 2016 13:39:40 -0400
Subject: [PATCH] Expand list interpolation to lists and maps

Allow lists and maps within the list interpolation function via variable
interpolation. Since this requires setting the variadic type to TypeAny,
we check for non-heterogeneous lists in the callback.
---
 config/interpolate_funcs.go                   | 29 ++++++++--
 config/interpolate_funcs_test.go              | 55 ++++++++++++++++++-
 .../docs/configuration/interpolation.html.md  |  2 +-
 3 files changed, 79 insertions(+), 7 deletions(-)

diff --git a/config/interpolate_funcs.go b/config/interpolate_funcs.go
index f73df85e6..a3cdf828b 100644
--- a/config/interpolate_funcs.go
+++ b/config/interpolate_funcs.go
@@ -91,15 +91,34 @@ func interpolationFuncList() ast.Function {
 		ArgTypes:     []ast.Type{},
 		ReturnType:   ast.TypeList,
 		Variadic:     true,
-		VariadicType: ast.TypeString,
+		VariadicType: ast.TypeAny,
 		Callback: func(args []interface{}) (interface{}, error) {
-			var outputList []string
+			var outputList []ast.Variable
 
-			for _, val := range args {
-				outputList = append(outputList, val.(string))
+			for i, val := range args {
+				switch v := val.(type) {
+				case string:
+					outputList = append(outputList, ast.Variable{Type: ast.TypeString, Value: v})
+				case []ast.Variable:
+					outputList = append(outputList, ast.Variable{Type: ast.TypeList, Value: v})
+				case map[string]ast.Variable:
+					outputList = append(outputList, ast.Variable{Type: ast.TypeMap, Value: v})
+				default:
+					return nil, fmt.Errorf("unexpected type %T for argument %d in list", v, i)
+				}
 			}
 
-			return stringSliceToVariableValue(outputList), nil
+			// we don't support heterogeneous types, so make sure all types match the first
+			if len(outputList) > 0 {
+				firstType := outputList[0].Type
+				for i, v := range outputList[1:] {
+					if v.Type != firstType {
+						return nil, fmt.Errorf("unexpected type %s for argument %d in list", v.Type, i+1)
+					}
+				}
+			}
+
+			return outputList, nil
 		},
 	}
 }
diff --git a/config/interpolate_funcs_test.go b/config/interpolate_funcs_test.go
index 7ee10372f..5b9800c14 100644
--- a/config/interpolate_funcs_test.go
+++ b/config/interpolate_funcs_test.go
@@ -38,7 +38,28 @@ func TestInterpolateFuncList(t *testing.T) {
 
 			// not a string input gives error
 			{
-				`${list("hello", "${var.list}")}`,
+				`${list("hello", 42)}`,
+				nil,
+				true,
+			},
+
+			// list of lists
+			{
+				`${list("${var.list}", "${var.list2}")}`,
+				[]interface{}{[]interface{}{"Hello", "World"}, []interface{}{"bar", "baz"}},
+				false,
+			},
+
+			// list of maps
+			{
+				`${list("${var.map}", "${var.map2}")}`,
+				[]interface{}{map[string]interface{}{"key": "bar"}, map[string]interface{}{"key2": "baz"}},
+				false,
+			},
+
+			// error on a heterogeneous list
+			{
+				`${list("first", "${var.list}")}`,
 				nil,
 				true,
 			},
@@ -57,6 +78,38 @@ func TestInterpolateFuncList(t *testing.T) {
 					},
 				},
 			},
+			"var.list2": {
+				Type: ast.TypeList,
+				Value: []ast.Variable{
+					{
+						Type:  ast.TypeString,
+						Value: "bar",
+					},
+					{
+						Type:  ast.TypeString,
+						Value: "baz",
+					},
+				},
+			},
+
+			"var.map": {
+				Type: ast.TypeMap,
+				Value: map[string]ast.Variable{
+					"key": {
+						Type:  ast.TypeString,
+						Value: "bar",
+					},
+				},
+			},
+			"var.map2": {
+				Type: ast.TypeMap,
+				Value: map[string]ast.Variable{
+					"key2": {
+						Type:  ast.TypeString,
+						Value: "baz",
+					},
+				},
+			},
 		},
 	})
 }
diff --git a/website/source/docs/configuration/interpolation.html.md b/website/source/docs/configuration/interpolation.html.md
index b2f66efd2..338550377 100644
--- a/website/source/docs/configuration/interpolation.html.md
+++ b/website/source/docs/configuration/interpolation.html.md
@@ -172,7 +172,7 @@ The supported built-in functions are:
       This function provides a way of representing list literals in interpolation.
       * `${list("a", "b", "c")}` returns a list of `"a", "b", "c"`.
       * `${list()}` returns an empty list.
- 
+
   * `lookup(map, key [, default])` - Performs a dynamic lookup into a mapping
       variable. The `map` parameter should be another variable, such
       as `var.amis`. If `key` does not exist in `map`, the interpolation will