add support for the chokidar library

Author: erik-krogh

javascript/change-notes/2021-06-22-chokidar.md

@@ -0,0 +1,5 @@
+lgtm,codescanning
+* Support for `chokidar` has improved. The `js/tainted-path` query recognized calls to `chokidar.watch`, 
+  and the security queries recognize the filenames returned by the library.
+  Affected packages are
+    [chokidar](https://npmjs.com/package/chokidar)

javascript/ql/src/semmle/javascript/frameworks/Files.qll

@@ -452,3 +452,21 @@ private class LibraryAccess extends FileSystemAccess, DataFlow::InvokeNode {
 
   override DataFlow::Node getAPathArgument() { result = getArgument(pathArgument) }
 }
+
+/**
+ * A call to the library [`chokidar`](https://www.npmjs.com/package/chokidar), where a call to `on` receives file names.
+ */
+class Chokidar extends FileNameProducer, FileSystemAccess, API::CallNode {
+  Chokidar() { this = API::moduleImport("chokidar").getMember("watch").getACall() }
+
+  override DataFlow::Node getAPathArgument() { result = getArgument(0) }
+
+  override DataFlow::Node getAFileName() {
+    exists(DataFlow::CallNode onCall, int pathIndex |
+      onCall = getAChainedMethodCall("on") and
+      if onCall.getArgument(0).mayHaveStringValue("all") then pathIndex = 1 else pathIndex = 0
+    |
+      result = onCall.getCallback(1).getParameter(pathIndex)
+    )
+  }
+}

javascript/ql/test/library-tests/frameworks/Concepts/tests.expected

@@ -34,6 +34,7 @@ getPathArgument
 | tst-file-names.js:44:12:44:49 | globule ... o.js"]) | tst-file-names.js:44:39:44:48 | ["foo.js"] |
 | tst-file-names.js:46:12:46:51 | globule ... .js"]}) | tst-file-names.js:46:34:46:49 | ["a.js", "b.js"] |
 | tst-file-names.js:47:12:47:52 | globule ... b.js"]) | tst-file-names.js:47:28:47:51 | ["foo/a ... /b.js"] |
+| tst-file-names.js:55:1:55:19 | chokidar.watch('.') | tst-file-names.js:55:16:55:18 | '.' |
 getReadNode
 | file-access.js:25:1:25:59 | jsonfil ... bj) {}) | file-access.js:25:52:25:54 | obj |
 | file-access.js:26:1:26:39 | jsonfil ... .json') | file-access.js:26:1:26:39 | jsonfil ... .json') |
@@ -78,6 +79,9 @@ fileNameSource
 | tst-file-names.js:46:12:46:51 | globule ... .js"]}) |
 | tst-file-names.js:47:12:47:52 | globule ... b.js"]) |
 | tst-file-names.js:51:15:51:23 | await foo |
+| tst-file-names.js:56:22:56:25 | path |
+| tst-file-names.js:59:17:59:20 | path |
+| tst-file-names.js:62:16:62:19 | path |
 persistentReadAccess_getAWrite
 | persistence.js:3:5:3:33 | localSt ... prop1') | persistence.js:2:5:2:37 | localSt ... 1', v1) |
 | persistence.js:6:5:6:35 | session ... prop2') | persistence.js:5:5:5:39 | session ... 2', v2) |

javascript/ql/test/library-tests/frameworks/Concepts/tst-file-names.js

@@ -49,4 +49,16 @@ var map3 = globule.mapping(["foo/a.js", "foo/b.js"])
 async function bar() {
   var foo = globby(_);
   var files = await foo;
-}
+}
+
+const chokidar = require('chokidar');
+chokidar.watch('.')
+  .on('all', (event, path) => {
+    console.log(event, path);
+  })
+  .on('change', path => {
+    console.log(path);
+  })
+  .on('ready', path => {
+    console.log(path);
+  });