JS: Implement some PackageJson members using new path resolution

Author: asgerf

javascript/ql/lib/semmle/javascript/NPM.qll

@@ -4,6 +4,7 @@
 
 import javascript
 private import NodeModuleResolutionImpl
+private import semmle.javascript.internal.paths.PackageJsonEx
 
 /** A `package.json` configuration object. */
 class PackageJson extends JsonObject {
@@ -93,7 +94,10 @@ class PackageJson extends JsonObject {
    * `module` paths to be exported under the relative path `"."`.
    */
   string getExportedPath(string relativePath) {
-    result = MainModulePath::of(this, relativePath).getValue()
+    this.(PackageJsonEx).hasExactPathMapping(relativePath, result)
+    or
+    relativePath = "." and
+    result = this.(PackageJsonEx).getMainPath()
   }
 
   /** Gets the path of a command defined for this package. */
@@ -220,20 +224,18 @@ class PackageJson extends JsonObject {
   /**
    * Gets the main module of this package.
    */
-  Module getMainModule() { result = this.getExportedModule(".") }
+  Module getMainModule() { result.getFile() = this.(PackageJsonEx).getMainFileOrBestGuess() }
 
   /**
    * Gets the module exported under the given relative path.
    *
    * The main module is considered exported under the path `"."`.
    */
   Module getExportedModule(string relativePath) {
-    result =
-      min(Module m, int prio |
-        m.getFile() = resolveMainModule(this, prio, relativePath)
-      |
-        m order by prio
-      )
+    this.(PackageJsonEx).hasExactPathMappingTo(relativePath, result.getFile())
+    or
+    relativePath = "." and
+    result = this.getMainModule()
   }
 
   /**