JS: do not resolve arbitrary extensions to JavaScript files

javascript/ql/src/semmle/javascript/Modules.qll

@@ -88,6 +88,7 @@ abstract class Module extends TopLevel {
         result = f.getJavaScriptFile(path.getBaseName())
         or
         // If a js file was not found look for a file that compiles to js
+        path.getExtension() = ".js" and
         not exists(f.getJavaScriptFile(path.getBaseName())) and
         result = f.getJavaScriptFile(path.getStem())
       )

javascript/ql/src/semmle/javascript/Paths.qll

@@ -128,6 +128,14 @@ abstract class PathString extends string {
   /** Gets the path of the parent folder of the folder or file this path refers to. */
   string getDirName() { result = this.regexpCapture(pathRegex(), 1) }
 
+  /**
+   * Gets the extension of the folder or file this path refers to, that is, the suffix of the base name
+   * starting at the last dot character, if there is one.
+   *
+   * Has no result if the base name does not contain a dot.
+   */
+  string getExtension() { result = this.regexpCapture(pathRegex(), 4) }
+
   /**
    * Gets the absolute path that the sub-path consisting of the first `n`
    * components of this path refers to when resolved relative to the
@@ -208,6 +216,14 @@ abstract class PathExpr extends PathExprBase {
   /** Gets the stem, that is, base name without extension, of the folder or file this path refers to. */
   string getStem() { result = getValue().(PathString).getStem() }
 
+  /**
+   * Gets the extension of the folder or file this path refers to, that is, the suffix of the base name
+   * starting at the last dot character, if there is one.
+   *
+   * Has no result if the base name does not contain a dot.
+   */
+  string getExtension() { result = getValue().(PathString).getExtension() }
+
   /**
    * Gets the file or folder that the first `n` components of this path refer to
    * when resolved relative to the root folder of the given `priority`.