Keep uppercase characters in kernel language names

Converting to lowercase was done arbitrarily.  So that one could write
`(jupyter-lang wolfram-language)` instead of
`(jupyter-lang Wolfram-Language)`.

fixes #241

* CHANGELOG.org: Add note.

* README.org: Update relevant sections.

* jupyter-base.el (jupyter-canonicalize-language-string): Do it.

* ob-jupyter.el (org-babel-jupyter-aliases-from-kernelspecs):

CHANGELOG.org

@@ -1,3 +1,9 @@
+* master
+
+- Fixed regression due to uppercase characters in kernel language
+  names, e.g. R.  =emacs-jupyter= would not work at all with language
+  specific features.
+
 * v0.8.2
 
 - Fix recursive loading error caused by =jupyter-tramp.el= autoloads.

README.org

@@ -419,10 +419,9 @@ to change the defaults for the =julia= kernel, you can set
 #+END_SRC
 *** Note on the language name provided by a kernelspec
 
-Some kernelspecs use spaces or uppercase characters in the name of the kernel
-language. Those get replaced by dashes or lowercase characters in the language
-name you need to use for the source block, e.g. =Wolfram Language=
-becomes =jupyter-wolfram-language=.
+Some kernelspecs use spaces in the name of the kernel language. Those
+get replaced by dashes in the language name you need to use for the
+source block, e.g. =Wolfram Language= becomes =jupyter-Wolfram-Language=.
 
 *** Integration with =ob-async=
 
@@ -1427,9 +1426,9 @@ kernel language is =julia= for indenting the current line:
   (call-interactively #'julia-latexsub-or-indent))
 #+END_SRC
 
-Note, when spaces or uppercase characters appear in the name of the kernel
-language they become dashes or lowercase characters in the symbol used for
-the =jupyter-lang= context, e.g. =Wolfram Language= becomes =wolfram-language=.
+Note, when spaces appear in the name of the kernel language they
+become dashes in the symbol used for the =jupyter-lang= context,
+e.g. =Wolfram Language= becomes =Wolfram-Language=.
 
 There are many other entry points where methods may be overridden in such a
 way. Below is the full list of methods that can be overridden in this way

jupyter-base.el

@@ -537,12 +537,14 @@ Note only SSH tunnels are currently supported."
 ;;; Helper functions
 
 (defun jupyter-canonicalize-language-string (str)
-  "Return STR with \" \" converted to \"-\" and all characters in lower case."
+  "Return STR with \" \" converted to \"-\".
+The `file-name-nondirectory' of STR will be converted and
+returned if it looks like a file path."
   ;; The call to `file-name-nondirectory' is here to be more robust when
   ;; running on systems like Guix or Nix. Some builders on those kinds of
   ;; systems will indiscriminately replace "python" with something like
   ;; "/gnu/store/.../bin/python" when building the kernelspecs.
-  (downcase (replace-regexp-in-string " " "-" (file-name-nondirectory str))))
+  (replace-regexp-in-string " " "-" (file-name-nondirectory str)))
 
 (defvar server-buffer)
 (defvar jupyter-current-client)

ob-jupyter.el

@@ -636,11 +636,10 @@ SPECS defaults to `jupyter-available-kernelspecs'.  Optional
 argument REFRESH has the same meaning as in
 `jupyter-available-kernelspecs'.
 
-Note, spaces or uppercase characters in the kernel language name
-are converted into dashes or lowercase characters in the language
-alias, e.g.
+Note, spaces in the kernel language name are converted into
+dashes in the language alias, e.g.
 
-    Wolfram Language -> jupyter-wolfram-language
+    Wolfram Language -> jupyter-Wolfram-Language
 
 For convenience, after creating a language alias for a kernel
 language LANG, set the :kernel default header argument if not

test/jupyter-test.el

@@ -678,7 +678,8 @@
 (ert-deftest jupyter-canonicalize-language-string ()
   :tags '(base env)
   (should (equal (jupyter-canonicalize-language-string "Wolfram Language")
-                 "wolfram-language"))
+                 "Wolfram-Language"))
+  (should (equal (jupyter-canonicalize-language-string "R") "R"))
   (should (equal (jupyter-canonicalize-language-string "/gnu/store/python")
                  "python")))