Python: Add wrapper for isPreferredModuleForName

We talked about how it's annoying that we in 4 places have the same fix
`isPreferredModuleForName(<module>.getFile(), <name> + ["", ".__init__"])`
, and that it would be nice to have a simple wrapper predicate that
ensures we never forget to do the `+ ["", ".__init__"]` dance...

I had trouble coming up with a name for this (ironically), but
I think `getModuleFromName` is good enough.

Author: RasmusWL

python/ql/lib/semmle/python/dataflow/new/internal/ImportResolution.qll

@@ -167,9 +167,22 @@ module ImportResolution {
     )
   }
 
+  /**
+   * Gets the (most likely) module for the name `name`, if any.
+   *
+   * Handles the fact that for the name `<pkg>` representing a package the actual module
+   * is `<pkg>.__init__`.
+   *
+   * See `isPreferredModuleForName` for more details on what "most likely" module means.
+   */
+  pragma[inline]
+  private Module getModuleFromName(string name) {
+    isPreferredModuleForName(result.getFile(), name + ["", ".__init__"])
+  }
+
   /** Gets the module from which attributes are imported by `i`. */
   Module getModuleImportedByImportStar(ImportStar i) {
-    isPreferredModuleForName(result.getFile(), i.getImportedModuleName() + ["", ".__init__"])
+    result = getModuleFromName(i.getImportedModuleName())
   }
 
   /**
@@ -224,7 +237,7 @@ module ImportResolution {
     exists(string module_name | result = getReferenceToModuleName(module_name) |
       // Depending on whether the referenced module is a package or not, we may need to add a
       // trailing `.__init__` to the module name.
-      isPreferredModuleForName(m.getFile(), module_name + ["", ".__init__"])
+      m = getModuleFromName(module_name)
       or
       // Module defined via `sys.modules`
       m = sys_modules_module_with_name(module_name)
@@ -235,7 +248,7 @@ module ImportResolution {
       ar.accesses(getModuleReference(p), attr_name) and
       result = ar
     |
-      isPreferredModuleForName(m.getFile(), p.getPackageName() + "." + attr_name + ["", ".__init__"])
+      m = getModuleFromName(p.getPackageName() + "." + attr_name)
     )
     or
     // This is also true for attributes that come from reexports.
@@ -249,8 +262,7 @@ module ImportResolution {
     exists(string submodule, Module package |
       SsaSource::init_module_submodule_defn(result.asVar().getSourceVariable(),
         package.getEntryNode()) and
-      isPreferredModuleForName(m.getFile(),
-        package.getPackageName() + "." + submodule + ["", ".__init__"])
+      m = getModuleFromName(package.getPackageName() + "." + submodule)
     )
   }