detect uses of jsxFactory and jsxFragmentFactory in js/unused-local-variable

javascript/ql/src/Declarations/UnusedVariable.ql

@@ -58,6 +58,16 @@ predicate isReactForJSX(UnusedLocal v) {
         plugin.getJsxFactoryVariableName() = v.getName()
       )
     )
+    or
+    exists(JSONObject tsconfig |
+      tsconfig.isTopLevel() and tsconfig.getFile().getBaseName() = "tsconfig.json"
+    |
+      v.getName() =
+        tsconfig
+            .getPropValue("compilerOptions")
+            .(JSONObject)
+            .getPropStringValue(["jsxFactory", "jsxFragmentFactory"])
+    )
   )
 }
 

javascript/ql/test/query-tests/Declarations/UnusedVariable/ts/tsconfig.json

@@ -0,0 +1,6 @@
+{
+    "compilerOptions": {
+        "jsx": "react",
+        "jsxFactory": "m"
+    }
+}

javascript/ql/test/query-tests/Declarations/UnusedVariable/ts/usesreact.tsx

@@ -0,0 +1,5 @@
+import {m} from 'some-react-library';
+
+export default function doAThing() {
+    return <span>foo</span>;
+}