[Fix] no-unused-prop-types: improve component declared props detection

Fixes #2752.

Author: jzabala

lib/util/Components.js

@@ -16,6 +16,7 @@ const propTypesUtil = require('./propTypes');
 const jsxUtil = require('./jsx');
 const usedPropTypesUtil = require('./usedPropTypes');
 const defaultPropsUtil = require('./defaultProps');
+const isFirstLetterCapitalized = require('./isFirstLetterCapitalized');
 
 function getId(node) {
   return node && node.range.join(':');
@@ -70,14 +71,6 @@ function isReturnsLogicalJSX(node, property, strict) {
     : (returnsLogicalJSXLeft || returnsLogicalJSXRight);
 }
 
-function isFirstLetterCapitalized(word) {
-  if (!word) {
-    return false;
-  }
-  const firstLetter = word.charAt(0);
-  return firstLetter.toUpperCase() === firstLetter;
-}
-
 const Lists = new WeakMap();
 
 /**

lib/util/isFirstLetterCapitalized.js

@@ -0,0 +1,16 @@
+'use strict';
+
+/**
+ * Check if the first letter of a string is capitalized.
+ * @param {String} word String to check
+ * @returns {Boolean} True if first letter is capitalized.
+ */
+function isFirstLetterCapitalized(word) {
+  if (!word) {
+    return false;
+  }
+  const firstLetter = word.charAt(0);
+  return firstLetter.toUpperCase() === firstLetter;
+}
+
+module.exports = isFirstLetterCapitalized;

lib/util/propTypes.js

@@ -12,6 +12,7 @@ const variableUtil = require('./variable');
 const versionUtil = require('./version');
 const propWrapperUtil = require('./propWrapper');
 const astUtil = require('./ast');
+const isFirstLetterCapitalized = require('./isFirstLetterCapitalized');
 
 /**
  * Check if node is function type.
@@ -83,6 +84,13 @@ function isInsideClassBody(node) {
   return false;
 }
 
+function startWithCapitalizedLetter(node) {
+  return (
+    node.parent.type === 'VariableDeclarator'
+    && !isFirstLetterCapitalized(node.parent.id.name)
+  );
+}
+
 module.exports = function propTypesInstructions(context, components, utils) {
   // Used to track the type annotations in scope.
   // Necessary because babel's scopes do not track type annotations.
@@ -878,7 +886,7 @@ module.exports = function propTypesInstructions(context, components, utils) {
     }
 
     // Should ignore function that not return JSXElement
-    if (!utils.isReturningJSXOrNull(node)) {
+    if (!utils.isReturningJSXOrNull(node) || startWithCapitalizedLetter(node)) {
       return;
     }
 

tests/lib/rules/no-unused-prop-types.js

@@ -3689,6 +3689,80 @@ ruleTester.run('no-unused-prop-types', rule, {
         }
         `,
         parser: parsers.BABEL_ESLINT
+      },
+      {
+        code: `
+        const Home = () => {
+          const renderStaticList = ({
+              item,
+          }: {
+              item: IContent;
+          }) => (
+              <Section
+                  icon={<FlashImage />}
+                  title={item.title}
+                  titleFontSize={theme.typography.FONT_SIZE_24}
+              >
+                  <StaticFlatList
+                      data={item.pointsOfSale}
+                      renderItem={renderStaticItem}
+                      keyExtractor={staticItemKeyExtractor}
+                  />
+              </Section>
+          );
+
+          return (
+              <SafeAreaViewWrapper>
+                  <LightStatusBar />
+                  <HomeFlatList
+                      ListHeaderComponent={listHeaderComponent}
+                      data={home?.static}
+                      renderItem={renderStaticList}
+                      keyExtractor={staticListKeyExtractor}
+                  />
+              </SafeAreaViewWrapper>
+          );
+        };
+        `,
+        parser: parsers['@TYPESCRIPT_ESLINT']
+      },
+      {
+        code: `
+        const Home = () => {
+          const renderStaticList = function({
+              item,
+          }: {
+              item: IContent;
+          }) {
+            return (
+              <Section
+                  icon={<FlashImage />}
+                  title={item.title}
+                  titleFontSize={theme.typography.FONT_SIZE_24}
+              >
+                  <StaticFlatList
+                      data={item.pointsOfSale}
+                      renderItem={renderStaticItem}
+                      keyExtractor={staticItemKeyExtractor}
+                  />
+              </Section>
+            )
+          };
+
+          return (
+              <SafeAreaViewWrapper>
+                  <LightStatusBar />
+                  <HomeFlatList
+                      ListHeaderComponent={listHeaderComponent}
+                      data={home?.static}
+                      renderItem={renderStaticList}
+                      keyExtractor={staticListKeyExtractor}
+                  />
+              </SafeAreaViewWrapper>
+          );
+        };
+        `,
+        parser: parsers['@TYPESCRIPT_ESLINT']
       }
     ])
   ),

tests/util/isFirstLetterCapitalized.js

@@ -0,0 +1,23 @@
+'use strict';
+
+const assert = require('assert');
+
+const isFirstLetterCapitalized = require('../../lib/util/isFirstLetterCapitalized');
+
+describe('isFirstLetterCapitalized', () => {
+  it('should return false for invalid input', () => {
+    assert.equal(isFirstLetterCapitalized(), false);
+    assert.equal(isFirstLetterCapitalized(null), false);
+    assert.equal(isFirstLetterCapitalized(''), false);
+  });
+
+  it('should return false for uncapitalized string', () => {
+    assert.equal(isFirstLetterCapitalized('isCapitalized'), false);
+    assert.equal(isFirstLetterCapitalized('lowercase'), false);
+  });
+
+  it('should return true for capitalized string', () => {
+    assert.equal(isFirstLetterCapitalized('IsCapitalized'), true);
+    assert.equal(isFirstLetterCapitalized('UPPERCASE'), true);
+  });
+});