JS: Move utility code into JSPaths

Author: asgerf

javascript/ql/lib/semmle/javascript/internal/paths/JSPaths.qll

@@ -6,6 +6,22 @@
 private import javascript
 private import semmle.javascript.TSConfig
 
+/**
+ * Holds if `path` is relative, in the sense that it should be resolved relative to its enclosing folder.
+ */
+bindingset[path]
+pragma[inline_late]
+predicate isRelativePath(string path) { path.regexpMatch("\\.\\.?(?:[/\\\\].*)?") }
+
+/**
+ * Gets the NPM package name from the beginning of the given import path, e.g.
+ * gets `foo` from `foo/bar`, and `@example/foo` from `@example/foo/bar`.
+ */
+bindingset[path]
+string getPackagePrefixFromString(string path) {
+  result = path.regexpFind("^(@[^/\\\\]+[/\\\\])?[^@./\\\\][^/\\\\]*", _, _)
+}
+
 /**
  * Gets a folder name that is a common source folder name.
  */

javascript/ql/lib/semmle/javascript/internal/paths/PathExprResolver.qll

@@ -88,20 +88,13 @@ module ResolveExpr<exprSig/1 shouldResolveExpr> {
     result.getAnAffectedFile() = expr.getFile()
   }
 
-  /**
-   * Holds if `path` is relative, in the sense that it should be resolved relative to its enclosing folder.
-   */
-  bindingset[path]
-  pragma[inline_late]
-  predicate isRelativePath(string path) { path.regexpMatch("\\.\\.?(?:[/\\\\].*)?") }
-
   /**
    * Gets the NPM package name from the beginning of the given import path, e.g.
    * gets `foo` from `foo/bar`, and `@example/foo` from `@example/foo/bar`.
    */
   pragma[nomagic]
   private string getPackagePrefixFromPathExpr(RelevantExpr expr) {
-    result = expr.getValue().regexpFind("^(@[^/\\\\]+[/\\\\])?[^@./\\\\][^/\\\\]*", _, _)
+    result = getPackagePrefixFromString(expr.getValue())
   }
 
   /**