fix(api): use more precise Flow types for public APIs. Fix #30

- Replaced Object type annotations with the required shape (not exact, can have extra attributes for convenience). This might raise type issues, but only if there is indeed a problem in the library usage. See [Flow’s `unclear-type`](https://flow.org/en/docs/linting/rule-reference/#toc-unclear-type) rule for further reference.
- Use [$ReadOnlyArray<T>](https://flow.org/en/docs/types/arrays/#toc-readonlyarray) in place of Array<T>. This is a supertype of Array (so no change required in implementation), which guarantees draftjs-filters does not mutate arrays.

src/lib/filters/atomic.js

@@ -79,7 +79,7 @@ export const resetAtomicBlocks = (content: ContentState) => {
  * Removes atomic blocks for which the entity isn't whitelisted.
  */
 export const removeInvalidAtomicBlocks = (
-  whitelist: Array<Object>,
+  whitelist: $ReadOnlyArray<{ type: string }>,
   content: ContentState,
 ) => {
   const blockMap = content.getBlockMap()

src/lib/filters/blocks.js

@@ -36,7 +36,7 @@ export const removeInvalidDepthBlocks = (content: ContentState) => {
  * ends up in the text. Other use cases may not be well covered.
  */
 export const preserveBlockByText = (
-  rules: Array<{
+  rules: $ReadOnlyArray<{
     test: string,
     type: string,
     depth: number,
@@ -125,7 +125,7 @@ export const limitBlockDepth = (max: number, content: ContentState) => {
  * Also sets depth to 0 (for potentially nested list items).
  */
 export const filterBlockTypes = (
-  whitelist: Array<string>,
+  whitelist: $ReadOnlyArray<string>,
   content: ContentState,
 ) => {
   const blockMap = content.getBlockMap()

src/lib/filters/editor.js

@@ -23,22 +23,23 @@ import {
 import { replaceTextBySpaces } from "./text"
 import { applyContentWithSelection } from "./selection"
 
+import { ContentState } from "draft-js"
 import type { EditorState as EditorStateType } from "draft-js"
 
 type FilterOptions = {
   // Whitelist of allowed block types. unstyled and atomic are always included.
-  blocks: Array<string>,
+  blocks: $ReadOnlyArray<string>,
   // Whitelist of allowed inline styles.
-  styles: Array<string>,
+  styles: $ReadOnlyArray<string>,
   // Whitelist of allowed entities.
-  entities: Array<{
+  entities: $ReadOnlyArray<{
     // Entity type, eg. "LINK"
     type: string,
     // Allowed attributes. Other attributes will be removed.
-    attributes: Array<string>,
+    attributes: $ReadOnlyArray<string>,
     // Refine which entities are kept by whitelisting acceptable values with regular expression patterns.
     whitelist: {
-      [attribute: string]: string,
+      [attribute: string]: string | boolean,
     },
   }>,
   // Maximum amount of depth for lists (0 = no nesting).
@@ -137,7 +138,7 @@ export const filterEditorState = (
 
   const content = editorState.getCurrentContent()
   const nextContent = filters.reduce(
-    (c, filter: Function) => filter(c),
+    (c, filter: (ContentState) => ContentState) => filter(c),
     content,
   )
 

src/lib/filters/entities.js

@@ -122,7 +122,7 @@ export const filterEntityRanges = (
  * Keeps all entity types (images, links, documents, embeds) that are enabled.
  */
 export const shouldKeepEntityType = (
-  whitelist: Array<Object>,
+  whitelist: $ReadOnlyArray<{ type: string }>,
   type: string,
 ) => {
   return whitelist.some((e) => e.type === type)
@@ -143,9 +143,14 @@ export const shouldRemoveImageEntity = (
  * Filters entities based on the data they contain.
  */
 export const shouldKeepEntityByAttribute = (
-  entityTypes: Array<Object>,
+  entityTypes: $ReadOnlyArray<{
+    type: string,
+    whitelist: {
+      [attribute: string]: string | boolean,
+    },
+  }>,
   entityType: string,
-  data: Object,
+  data: {},
 ) => {
   const config = entityTypes.find((t) => t.type === entityType)
   // If no whitelist is defined, the filter keeps the entity.
@@ -172,7 +177,10 @@ export const shouldKeepEntityByAttribute = (
  * of unneeded attributes (width, height, etc).
  */
 export const filterEntityData = (
-  entityTypes: Array<Object>,
+  entityTypes: $ReadOnlyArray<{
+    type: string,
+    attributes: $ReadOnlyArray<string>,
+  }>,
   content: ContentState,
 ) => {
   let newContent = content

src/lib/filters/styles.js

@@ -5,7 +5,7 @@ import { ContentState, CharacterMetadata } from "draft-js"
  * Removes all styles not present in the whitelist.
  */
 export const filterInlineStyles = (
-  whitelist: Array<string>,
+  whitelist: $ReadOnlyArray<string>,
   content: ContentState,
 ) => {
   const blockMap = content.getBlockMap()

src/lib/filters/text.js

@@ -5,7 +5,7 @@ import { ContentState } from "draft-js"
  * Replaces the given characters by their equivalent length of spaces, in all blocks.
  */
 export const replaceTextBySpaces = (
-  characters: Array<string>,
+  characters: $ReadOnlyArray<string>,
   content: ContentState,
 ) => {
   const blockMap = content.getBlockMap()