From 6455efa5d327377b41e708a063d1b7a71a131165 Mon Sep 17 00:00:00 2001
From: Matthew Holt <mholt@users.noreply.github.com>
Date: Tue, 17 Dec 2019 10:11:45 -0700
Subject: admin: POST /... expands and appends all array elements

Makes it easy to append many items to an array in one command
---
 admin.go      | 39 +++++++++++++++++++++++++++++++++------
 admin_test.go |  6 ++++++
 2 files changed, 39 insertions(+), 6 deletions(-)

diff --git a/admin.go b/admin.go
index 0f8144b..89c007d 100644
--- a/admin.go
+++ b/admin.go
@@ -636,6 +636,19 @@ func unsyncedConfigAccess(method, path string, body []byte, out io.Writer) error
 		return fmt.Errorf("path missing")
 	}
 
+	// A path that ends with "..." implies:
+	// 1) the part before it is an array
+	// 2) the payload is an array
+	// and means that the user wants to expand the elements
+	// in the payload array and append each one into the
+	// destination array, like so:
+	//     array = append(array, elems...)
+	// This special case is handled below.
+	ellipses := parts[len(parts)-1] == "..."
+	if ellipses {
+		parts = parts[:len(parts)-1]
+	}
+
 	var ptr interface{} = rawCfg
 
 traverseLoop:
@@ -666,7 +679,15 @@ traverseLoop:
 						return fmt.Errorf("encoding config: %v", err)
 					}
 				case http.MethodPost:
-					v[part] = append(arr, val)
+					if ellipses {
+						valArray, ok := val.([]interface{})
+						if !ok {
+							return fmt.Errorf("final element is not an array")
+						}
+						v[part] = append(arr, valArray...)
+					} else {
+						v[part] = append(arr, val)
+					}
 				case http.MethodPut:
 					// avoid creation of new slice and a second copy (see
 					// https://github.com/golang/go/wiki/SliceTricks#insert)
@@ -692,13 +713,19 @@ traverseLoop:
 						return fmt.Errorf("encoding config: %v", err)
 					}
 				case http.MethodPost:
+					// if the part is an existing list, POST appends to
+					// it, otherwise it just sets or creates the value
 					if arr, ok := v[part].([]interface{}); ok {
-						// if the part is an existing list, POST appends to it
-						// TODO: Do we ever reach this point, since we handle arrays
-						// separately above?
-						v[part] = append(arr, val)
+						if ellipses {
+							valArray, ok := val.([]interface{})
+							if !ok {
+								return fmt.Errorf("final element is not an array")
+							}
+							v[part] = append(arr, valArray...)
+						} else {
+							v[part] = append(arr, val)
+						}
 					} else {
-						// otherwise, it simply sets the value
 						v[part] = val
 					}
 				case http.MethodPut:
diff --git a/admin_test.go b/admin_test.go
index e8563b7..cfb4ab7 100644
--- a/admin_test.go
+++ b/admin_test.go
@@ -77,6 +77,12 @@ func TestUnsyncedConfigAccess(t *testing.T) {
 			payload: `"d"`,
 			expect:  `{"foo": "jet", "bar": {"aa": "bb"}, "list": ["a", "b", "c", "d"]}`,
 		},
+		{
+			method:  "POST",
+			path:    "/list/...",
+			payload: `["e", "f", "g"]`,
+			expect:  `{"foo": "jet", "bar": {"aa": "bb"}, "list": ["a", "b", "c", "d", "e", "f", "g"]}`,
+		},
 	} {
 		err := unsyncedConfigAccess(tc.method, rawConfigKey+tc.path, []byte(tc.payload), nil)
 
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