1 files changed, 151 insertions, 0 deletions
diff --git a/popperjs/package/lib/utils/validateModifiers.js.flow b/popperjs/package/lib/utils/validateModifiers.js.flow
new file mode 100644
index 0000000..889e5a3
--- /dev/null
+++ b/popperjs/package/lib/utils/validateModifiers.js.flow
@@ -0,0 +1,151 @@
+// @flow
+import format from './format';
+import { modifierPhases } from '../enums';
+
+const INVALID_MODIFIER_ERROR =
+  'Popper: modifier "%s" provided an invalid %s property, expected %s but got %s';
+const MISSING_DEPENDENCY_ERROR =
+  'Popper: modifier "%s" requires "%s", but "%s" modifier is not available';
+const VALID_PROPERTIES = [
+  'name',
+  'enabled',
+  'phase',
+  'fn',
+  'effect',
+  'requires',
+  'options',
+];
+
+export default function validateModifiers(modifiers: Array<any>): void {
+  modifiers.forEach((modifier) => {
+    [...Object.keys(modifier), ...VALID_PROPERTIES]
+      // IE11-compatible replacement for `new Set(iterable)`
+      .filter((value, index, self) => self.indexOf(value) === index)
+      .forEach((key) => {
+        switch (key) {
+          case 'name':
+            if (typeof modifier.name !== 'string') {
+              console.error(
+                format(
+                  INVALID_MODIFIER_ERROR,
+                  String(modifier.name),
+                  '"name"',
+                  '"string"',
+                  `"${String(modifier.name)}"`
+                )
+              );
+            }
+            break;
+          case 'enabled':
+            if (typeof modifier.enabled !== 'boolean') {
+              console.error(
+                format(
+                  INVALID_MODIFIER_ERROR,
+                  modifier.name,
+                  '"enabled"',
+                  '"boolean"',
+                  `"${String(modifier.enabled)}"`
+                )
+              );
+            }
+            break;
+          case 'phase':
+            if (modifierPhases.indexOf(modifier.phase) < 0) {
+              console.error(
+                format(
+                  INVALID_MODIFIER_ERROR,
+                  modifier.name,
+                  '"phase"',
+                  `either ${modifierPhases.join(', ')}`,
+                  `"${String(modifier.phase)}"`
+                )
+              );
+            }
+            break;
+          case 'fn':
+            if (typeof modifier.fn !== 'function') {
+              console.error(
+                format(
+                  INVALID_MODIFIER_ERROR,
+                  modifier.name,
+                  '"fn"',
+                  '"function"',
+                  `"${String(modifier.fn)}"`
+                )
+              );
+            }
+            break;
+          case 'effect':
+            if (
+              modifier.effect != null &&
+              typeof modifier.effect !== 'function'
+            ) {
+              console.error(
+                format(
+                  INVALID_MODIFIER_ERROR,
+                  modifier.name,
+                  '"effect"',
+                  '"function"',
+                  `"${String(modifier.fn)}"`
+                )
+              );
+            }
+            break;
+          case 'requires':
+            if (
+              modifier.requires != null &&
+              !Array.isArray(modifier.requires)
+            ) {
+              console.error(
+                format(
+                  INVALID_MODIFIER_ERROR,
+                  modifier.name,
+                  '"requires"',
+                  '"array"',
+                  `"${String(modifier.requires)}"`
+                )
+              );
+            }
+            break;
+          case 'requiresIfExists':
+            if (!Array.isArray(modifier.requiresIfExists)) {
+              console.error(
+                format(
+                  INVALID_MODIFIER_ERROR,
+                  modifier.name,
+                  '"requiresIfExists"',
+                  '"array"',
+                  `"${String(modifier.requiresIfExists)}"`
+                )
+              );
+            }
+            break;
+          case 'options':
+          case 'data':
+            break;
+          default:
+            console.error(
+              `PopperJS: an invalid property has been provided to the "${
+                modifier.name
+              }" modifier, valid properties are ${VALID_PROPERTIES.map(
+                (s) => `"${s}"`
+              ).join(', ')}; but "${key}" was provided.`
+            );
+        }
+
+        modifier.requires &&
+          modifier.requires.forEach((requirement) => {
+            if (modifiers.find((mod) => mod.name === requirement) == null) {
+              console.error(
+                format(
+                  MISSING_DEPENDENCY_ERROR,
+                  String(modifier.name),
+                  requirement,
+                  requirement
+                )
+              );
+            }
+          });
+      });
+  });
+}