[clang-tidy] Non-private member variables in classes (MISRA, CppCoreGuidelines, HICPP)

Summary:
Finds classes that not only contain the data (non-static member variables),
but also have logic (non-static member functions), and diagnoses all member
variables that have any other scope other than `private`. They should be
made `private`, and manipulated exclusively via the member functions.

Optionally, classes with all member variables being `public` could be
ignored, and optionally all `public` member variables could be ignored.

Options
-------

* IgnoreClassesWithAllMemberVariablesBeingPublic

  Allows to completely ignore classes if **all** the member variables in that
  class have `public` visibility.

* IgnorePublicMemberVariables

  Allows to ignore (not diagnose) **all** the member variables with `public`
  visibility scope.

References:
* MISRA 11-0-1 Member data in non-POD class types shall be private.
* https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#c2-use-class-if-the-class-has-an-invariant-use-struct-if-the-data-members-can-vary-independently
* https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#Rc-private
* https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#Rh-protected

Reviewers: JonasToth, aaron.ballman, alexfh, hokein, xazax.hun

Reviewed By: aaron.ballman

Subscribers: Eugene.Zelenko, zinovy.nis, cfe-commits, rnkovacs, nemanjai, mgorny, xazax.hun, kbarton

Tags: #clang-tools-extra

Differential Revision: https://reviews.llvm.org/D52771

4 files changed, 52 insertions, 0 deletions

diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index 17be5cea258..1af6d050206 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -103,6 +103,13 @@ Improvements to clang-tidy
   Flags uses of ``absl::StrCat()`` to append to a ``std::string``. Suggests
   ``absl::StrAppend()`` should be used instead.
 
+- New :doc:`misc-non-private-member-variables-in-classes
+  <clang-tidy/checks/misc-non-private-member-variables-in-classes>` check.
+
+  Finds classes that not only contain the data (non-static member variables),
+  but also have logic (non-static member functions), and diagnoses all member
+  variables that have any other scope other than ``private``.
+
 - New :doc:`modernize-concat-nested-namespaces
   <clang-tidy/checks/modernize-concat-nested-namespaces>` check.
 
@@ -134,6 +141,12 @@ Improvements to clang-tidy
   <clang-tidy/checks/readability-uppercase-literal-suffix>`
   added.
 
+- New alias :doc:`cppcoreguidelines-non-private-member-variables-in-classes
+  <clang-tidy/checks/cppcoreguidelines-non-private-member-variables-in-classes>`
+  to :doc:`misc-non-private-member-variables-in-classes
+  <clang-tidy/checks/misc-non-private-member-variables-in-classes>`
+  added.
+
 - New alias :doc:`hicpp-uppercase-literal-suffix
   <clang-tidy/checks/hicpp-uppercase-literal-suffix>` to
   :doc:`readability-uppercase-literal-suffix
diff --git a/clang-tools-extra/docs/clang-tidy/checks/cppcoreguidelines-non-private-member-variables-in-classes.rst b/clang-tools-extra/docs/clang-tidy/checks/cppcoreguidelines-non-private-member-variables-in-classes.rst
new file mode 100644
index 00000000000..293e1bbe094
--- /dev/null
+++ b/clang-tools-extra/docs/clang-tidy/checks/cppcoreguidelines-non-private-member-variables-in-classes.rst
@@ -0,0 +1,11 @@
+.. title:: clang-tidy - cppcoreguidelines-non-private-member-variables-in-classes
+.. meta::
+   :http-equiv=refresh: 5;URL=misc-non-private-member-variables-in-classes.html
+
+cppcoreguidelines-non-private-member-variables-in-classes
+=========================================================
+
+The cppcoreguidelines-non-private-member-variables-in-classes check is an alias,
+please see
+`misc-non-private-member-variables-in-classes <misc-non-private-member-variables-in-classes.html>`_
+for more information.
diff --git a/clang-tools-extra/docs/clang-tidy/checks/list.rst b/clang-tools-extra/docs/clang-tidy/checks/list.rst
index f5d4ac898ce..fc915d75b76 100644
--- a/clang-tools-extra/docs/clang-tidy/checks/list.rst
+++ b/clang-tools-extra/docs/clang-tidy/checks/list.rst
@@ -91,6 +91,7 @@ Clang-Tidy Checks
    cppcoreguidelines-interfaces-global-init
    cppcoreguidelines-narrowing-conversions
    cppcoreguidelines-no-malloc
+   cppcoreguidelines-non-private-member-variables-in-classes (redirects to misc-non-private-member-variables-in-classes) <cppcoreguidelines-non-private-member-variables-in-classes>
    cppcoreguidelines-owning-memory
    cppcoreguidelines-pro-bounds-array-to-pointer-decay
    cppcoreguidelines-pro-bounds-constant-array-index
@@ -165,6 +166,7 @@ Clang-Tidy Checks
    misc-misplaced-const
    misc-new-delete-overloads
    misc-non-copyable-objects
+   misc-non-private-member-variables-in-classes
    misc-redundant-expression
    misc-static-assert
    misc-throw-by-value-catch-by-reference
diff --git a/clang-tools-extra/docs/clang-tidy/checks/misc-non-private-member-variables-in-classes.rst b/clang-tools-extra/docs/clang-tidy/checks/misc-non-private-member-variables-in-classes.rst
new file mode 100644
index 00000000000..db88c9b1cff
--- /dev/null
+++ b/clang-tools-extra/docs/clang-tidy/checks/misc-non-private-member-variables-in-classes.rst
@@ -0,0 +1,26 @@
+.. title:: clang-tidy - misc-non-private-member-variables-in-classes
+
+misc-non-private-member-variables-in-classes
+============================================
+
+`cppcoreguidelines-non-private-member-variables-in-classes` redirects here
+as an alias for this check.
+
+Finds classes that contain non-static data members in addition to non-static
+member functions and diagnose all data members declared with a non-``public``
+access specifier. The data members should be declared as ``private`` and
+accessed through member functions instead of exposed to derived classes or
+class consumers.
+
+Options
+-------
+
+.. option:: IgnoreClassesWithAllMemberVariablesBeingPublic
+
+   Allows to completely ignore classes if **all** the member variables in that
+   class a declared with a ``public`` access specifier.
+
+.. option:: IgnorePublicMemberVariables
+
+   Allows to ignore (not diagnose) **all** the member variables declared with
+   a ``public`` access specifier.