Merge pull request #20348 from hashicorp/jbardin/list-empty-strings

simple list diffs may also have missing elements

builtin/providers/test/resource.go

@@ -171,7 +171,7 @@ func testResourceUpdate(d *schema.ResourceData, meta interface{}) error {
 	if errMsg != "" {
 		return errors.New(errMsg)
 	}
-	return nil
+	return testResourceRead(d, meta)
 }
 
 func testResourceDelete(d *schema.ResourceData, meta interface{}) error {

builtin/providers/test/resource_list.go

@@ -30,6 +30,13 @@ func testResourceList() *schema.Resource {
 							Optional: true,
 							ForceNew: true,
 						},
+						"sublist": {
+							Type:     schema.TypeList,
+							Optional: true,
+							Elem: &schema.Schema{
+								Type: schema.TypeString,
+							},
+						},
 						"sublist_block": {
 							Type:     schema.TypeList,
 							Optional: true,

builtin/providers/test/resource_list_test.go

@@ -218,3 +218,61 @@ resource "test_resource_list" "foo" {
 		},
 	})
 }
+
+func TestResourceList_emptyStrings(t *testing.T) {
+	resource.UnitTest(t, resource.TestCase{
+		Providers:    testAccProviders,
+		CheckDestroy: testAccCheckResourceDestroy,
+		Steps: []resource.TestStep{
+			resource.TestStep{
+				Config: strings.TrimSpace(`
+resource "test_resource_list" "foo" {
+  list_block {
+    sublist = ["a", ""]
+  }
+
+  list_block {
+    sublist = [""]
+  }
+
+  list_block {
+    sublist = ["", "c", ""]
+  }
+}
+				`),
+				Check: resource.ComposeTestCheckFunc(
+					resource.TestCheckResourceAttr("test_resource_list.foo", "list_block.0.sublist.0", "a"),
+					resource.TestCheckResourceAttr("test_resource_list.foo", "list_block.0.sublist.1", ""),
+					resource.TestCheckResourceAttr("test_resource_list.foo", "list_block.1.sublist.0", ""),
+					resource.TestCheckResourceAttr("test_resource_list.foo", "list_block.2.sublist.0", ""),
+					resource.TestCheckResourceAttr("test_resource_list.foo", "list_block.2.sublist.1", "c"),
+					resource.TestCheckResourceAttr("test_resource_list.foo", "list_block.2.sublist.2", ""),
+				),
+			},
+			resource.TestStep{
+				Config: strings.TrimSpace(`
+resource "test_resource_list" "foo" {
+  list_block {
+    sublist = [""]
+  }
+
+  list_block {
+    sublist = []
+  }
+
+  list_block {
+    sublist = ["", "c"]
+  }
+}
+			`),
+				Check: resource.ComposeTestCheckFunc(
+					resource.TestCheckResourceAttr("test_resource_list.foo", "list_block.0.sublist.#", "1"),
+					resource.TestCheckResourceAttr("test_resource_list.foo", "list_block.0.sublist.0", ""),
+					resource.TestCheckResourceAttr("test_resource_list.foo", "list_block.1.sublist.#", "0"),
+					resource.TestCheckResourceAttr("test_resource_list.foo", "list_block.2.sublist.1", "c"),
+					resource.TestCheckResourceAttr("test_resource_list.foo", "list_block.2.sublist.#", "2"),
+				),
+			},
+		},
+	})
+}

terraform/diff.go

@@ -624,7 +624,7 @@ func (d *InstanceDiff) applyBlockDiff(path []string, attrs map[string]string, sc
 						if err != nil {
 							// this shouldn't happen since we added these
 							// ourself, but make note of it just in case.
-							log.Printf("[ERROR] bas list index in %q: %s", k, err)
+							log.Printf("[ERROR] bad list index in %q: %s", k, err)
 							continue
 						}
 						if i >= length {
@@ -811,10 +811,61 @@ func (d *InstanceDiff) applyCollectionDiff(path []string, attrs map[string]strin
 		}
 	}
 
+	// Just like in nested list blocks, for simple lists we may need to fill in
+	// missing empty strings.
+	countKey := name + "." + idx
+	count := result[countKey]
+	length, _ := strconv.Atoi(count)
+
+	if count != "" && count != hcl2shim.UnknownVariableValue &&
+		attrSchema.Type.Equals(cty.List(cty.String)) {
+		// insert empty strings into missing indexes
+		for i := 0; i < length; i++ {
+			key := fmt.Sprintf("%s.%d", name, i)
+			if _, ok := result[key]; !ok {
+				result[key] = ""
+			}
+		}
+	}
+
+	// now check for truncation in any type of list
+	if attrSchema.Type.IsListType() {
+		for key := range result {
+			if key == countKey {
+				continue
+			}
+
+			if len(key) <= len(name)+1 {
+				// not sure what this is, but don't panic
+				continue
+			}
+
+			index := key[len(name)+1:]
+
+			// It is possible to have nested sets or maps, so look for another dot
+			dot := strings.Index(index, ".")
+			if dot > 0 {
+				index = index[:dot]
+			}
+
+			// This shouldn't have any more dots, since the element type is only string.
+			num, err := strconv.Atoi(index)
+			if err != nil {
+				log.Printf("[ERROR] bad list index in %q: %s", currentKey, err)
+				continue
+			}
+
+			if num >= length {
+				delete(result, key)
+			}
+		}
+	}
+
 	// Fill in the count value if it was missing for some reason:
-	if result[name+"."+idx] == "" {
-		result[name+"."+idx] = countFlatmapContainerValues(name+"."+idx, result)
+	if result[countKey] == "" {
+		result[countKey] = countFlatmapContainerValues(countKey, result)
 	}
+
 	return result, nil
 }