master 0b099e3 2/7: Use ambient lexical-binding value in ert-deftest body (bug#50738)

[Mattias Engdegård]

branch: master
commit 0b099e34dc726c3ed0e7b63028f42c2a2720ba7c
Author: Mattias Engdegård <mattiase@acm.org>
Commit: Mattias Engdegård <mattiase@acm.org>

    Use ambient lexical-binding value in ert-deftest body (bug#50738)
    
    * lisp/emacs-lisp/ert.el (ert-deftest):
    Evaluate the body of `ert-deftest` with the `lexical-binding` value of
    the source file (or more precisely the value in force when the
    definition is evaluated), which is what everyone expected, instead of
    always using dynamic binding which is what they got until now.
    * test/lisp/emacs-lisp/ert-tests.el
    (ert-test-deftest-lexical-binding-t): New test.
---
 lisp/emacs-lisp/ert.el            | 6 +++++-
 test/lisp/emacs-lisp/ert-tests.el | 4 ++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/lisp/emacs-lisp/ert.el b/lisp/emacs-lisp/ert.el
index d4d8510..6d867ab 100644
--- a/lisp/emacs-lisp/ert.el
+++ b/lisp/emacs-lisp/ert.el
@@ -218,7 +218,11 @@ it has to be wrapped in `(eval (quote ...))'.
                             `(:expected-result-type ,expected-result))
                         ,@(when tags-supplied-p
                             `(:tags ,tags))
-                        :body (lambda () ,@body)))
+                        :body (lambda ()
+                                ;; Use the value of `lexical-binding' in
+                                ;; the source file when evaluating the body.
+                                (let ((lexical-binding ,lexical-binding))
+                                  ,@body))))
          ',name))))
 
 (defvar ert--find-test-regexp
diff --git a/test/lisp/emacs-lisp/ert-tests.el 
b/test/lisp/emacs-lisp/ert-tests.el
index 5c96961..a18664b 100644
--- a/test/lisp/emacs-lisp/ert-tests.el
+++ b/test/lisp/emacs-lisp/ert-tests.el
@@ -816,6 +816,10 @@ This macro is used to test if macroexpansion in `should' 
works."
     (should (equal (ert-test-failed-condition result)
                    '(ert-test-failed "Boo")))))
 
+(ert-deftest ert-test-deftest-lexical-binding-t ()
+  "Check that `lexical-binding' in `ert-deftest' has the file value."
+  (should (equal lexical-binding t)))
+
 
 (provide 'ert-tests)