ob-shell.el: Delete `org-babel-shell-return-value-is-exit-status'

* lisp/ob-shell.el (org-babel-sh-evaluate): Return the output
by default.  Return exit status as the "value" when :result is
explicitely set to "value".

* lisp/ob-shell.el
(org-babel-shell-return-value-is-exit-status): Delete option.

* doc/org-manual.org (Collection): Be more accurate.

See the whole thread here:
https://lists.gnu.org/archive/html/emacs-orgmode/2020-02/msg00715.html

Thanks to everyone in this discussion.

doc/org-manual.org

@@ -17274,13 +17274,13 @@ they are mutually exclusive.
 
 - =value= ::
 
-  Default.  Functional mode.  Org gets the value by wrapping the code
-  in a function definition in the language of the source block.  That
-  is why when using =:results value=, code should execute like
-  a function and return a value.  For languages like Python, an
-  explicit ~return~ statement is mandatory when using =:results
-  value=.  Result is the value returned by the last statement in the
-  code block.
+  Default for most Babel libraries[fn:142].  Functional mode.  Org
+  gets the value by wrapping the code in a function definition in the
+  language of the source block.  That is why when using =:results
+  value=, code should execute like a function and return a value.  For
+  languages like Python, an explicit ~return~ statement is mandatory
+  when using =:results value=.  Result is the value returned by the
+  last statement in the code block.
 
   When evaluating the code block in a session (see [[*Environment of
   a Code Block]]), Org passes the code to an interpreter running as an
@@ -17873,10 +17873,10 @@ Code blocks in the following languages are supported.
 | Asymptote  | =asymptote=   | Lisp           | =lisp=       |
 | Awk        | =awk=         | Lua            | =lua=        |
 | C          | =C=           | MATLAB         | =matlab=     |
-| C++        | =C++=[fn:142] | Mscgen         | =mscgen=     |
+| C++        | =C++=[fn:143] | Mscgen         | =mscgen=     |
 | Clojure    | =clojure=     | Objective Caml | =ocaml=      |
 | CSS        | =css=         | Octave         | =octave=     |
-| D          | =D=[fn:143]   | Org mode       | =org=        |
+| D          | =D=[fn:144]   | Org mode       | =org=        |
 | ditaa      | =ditaa=       | Oz             | =oz=         |
 | Emacs Calc | =calc=        | Perl           | =perl=       |
 | Emacs Lisp | =emacs-lisp=  | Plantuml       | =plantuml=   |
@@ -18005,7 +18005,7 @@ for Python and Emacs Lisp languages.
 #+cindex: syntax, Noweb
 #+cindex: source code, Noweb reference
 
-Org supports named blocks in Noweb[fn:144] style syntax:
+Org supports named blocks in Noweb[fn:145] style syntax:
 
 : <<CODE-BLOCK-ID>>
 
@@ -18501,7 +18501,7 @@ Org Tempo expands snippets to structures defined in
 ~org-structure-template-alist~ and ~org-tempo-keywords-alist~.  For
 example, {{{kbd(< s TAB)}}} creates a code block.  Enable it by
 customizing ~org-modules~ or add =(require 'org-tempo)= to your Emacs
-init file[fn:145].
+init file[fn:146].
 
 #+attr_texinfo: :columns 0.1 0.9
 | {{{kbd(a)}}} | =#+BEGIN_EXPORT ascii= ... =#+END_EXPORT= |
@@ -18581,7 +18581,7 @@ in the desired amount with hard spaces and hiding leading stars.
 To display the buffer in the indented view, activate Org Indent minor
 mode, using {{{kbd(M-x org-indent-mode)}}}.  Text lines that are not
 headlines are prefixed with virtual spaces to vertically align with
-the headline text[fn:146].
+the headline text[fn:147].
 
 #+vindex: org-indent-indentation-per-level
 To make more horizontal space, the headlines are shifted by two
@@ -18609,9 +18609,9 @@ use =STARTUP= keyword as follows:
 
 It is possible to use hard spaces to achieve the indentation instead,
 if the bare ASCII file should have the indented look also outside
-Emacs[fn:147].  With Org's support, you have to indent all lines to
+Emacs[fn:148].  With Org's support, you have to indent all lines to
 line up with the outline headers.  You would use these
-settings[fn:148]:
+settings[fn:149]:
 
   #+begin_src emacs-lisp
   (setq org-adapt-indentation t
@@ -18878,7 +18878,7 @@ changes.
 
   #+vindex: org-startup-indented
   Dynamic virtual indentation is controlled by the variable
-  ~org-startup-indented~[fn:149].
+  ~org-startup-indented~[fn:150].
 
   | =indent=   | Start with Org Indent mode turned on.  |
   | =noindent= | Start with Org Indent mode turned off. |
@@ -19694,7 +19694,7 @@ Tags]]) only for those set in these variables.
 
 #+vindex: org-mobile-directory
 The mobile application needs access to a file directory on
-a server[fn:150] to interact with Emacs.  Pass its location through
+a server[fn:151] to interact with Emacs.  Pass its location through
 the ~org-mobile-directory~ variable.  If you can mount that directory
 locally just set the variable to point to that directory:
 
@@ -19715,7 +19715,7 @@ With a public server, consider encrypting the files.  Org also
 requires OpenSSL installed on the local computer.  To turn on
 encryption, set the same password in the mobile application and in
 Emacs.  Set the password in the variable
-~org-mobile-use-encryption~[fn:151].  Note that even after the mobile
+~org-mobile-use-encryption~[fn:152].  Note that even after the mobile
 application encrypts the file contents, the file name remains visible
 on the file systems of the local computer, the server, and the mobile
 device.
@@ -19731,15 +19731,15 @@ The command ~org-mobile-push~ copies files listed in
 ~org-mobile-files~ into the staging area.  Files include agenda files
 (as listed in ~org-agenda-files~).  Customize ~org-mobile-files~ to
 add other files.  File names are staged with paths relative to
-~org-directory~, so all files should be inside this directory[fn:152].
+~org-directory~, so all files should be inside this directory[fn:153].
 
 Push creates a special Org file =agendas.org= with custom agenda views
-defined by the user[fn:153].
+defined by the user[fn:154].
 
 Finally, Org writes the file =index.org=, containing links to other
 files.  The mobile application reads this file first from the server
 to determine what other files to download for agendas.  For faster
-downloads, it is expected to only read files whose checksums[fn:154]
+downloads, it is expected to only read files whose checksums[fn:155]
 have changed.
 
 *** Pulling from the mobile application
@@ -19756,7 +19756,7 @@ data in an inbox file format, through the following steps:
 
 1.
    #+vindex: org-mobile-inbox-for-pull
-   Org moves all entries found in =mobileorg.org=[fn:155] and appends
+   Org moves all entries found in =mobileorg.org=[fn:156] and appends
    them to the file pointed to by the variable
    ~org-mobile-inbox-for-pull~.  It should reside neither in the
    staging area nor on the server.  Each captured entry and each
@@ -20052,9 +20052,9 @@ of these strategies:
 #+cindex: @LaTeX{}, and Orgtbl mode
 
 To wrap a source table in LaTeX, use the =comment= environment
-provided by =comment.sty=[fn:156].  To activate it, put
+provided by =comment.sty=[fn:157].  To activate it, put
 ~\usepackage{comment}~ in the document header.  Orgtbl mode inserts
-a radio table skeleton[fn:157] with the command {{{kbd(M-x
+a radio table skeleton[fn:158] with the command {{{kbd(M-x
 orgtbl-insert-radio-table)}}}, which prompts for a table name.  For
 example, if =salesfigures= is the name, the template inserts:
 
@@ -20073,7 +20073,7 @@ The line =#+ORGTBL: SEND= tells Orgtbl mode to use the function
 ~orgtbl-to-latex~ to convert the table to LaTeX format, then insert
 the table at the target (receive) location named =salesfigures=.  Now
 the table is ready for data entry.  It can even use spreadsheet
-features[fn:158]:
+features[fn:159]:
 
 #+begin_example
 % BEGIN RECEIVE ORGTBL salesfigures
@@ -20289,7 +20289,7 @@ Dynamic blocks, like any other block, can be narrowed with
 #+vindex: org-agenda-skip-function
 #+vindex: org-agenda-skip-function-global
 Org provides a special hook to further limit items in agenda views:
-~agenda~, ~agenda*~[fn:159], ~todo~, ~alltodo~, ~tags~, ~tags-todo~,
+~agenda~, ~agenda*~[fn:160], ~todo~, ~alltodo~, ~tags~, ~tags-todo~,
 ~tags-tree~.  Specify a custom function that tests inclusion of every
 matched item in the view.  This function can also skip as much as is
 needed.
@@ -20332,7 +20332,7 @@ meaningful string suitable for the agenda view.
 #+vindex: org-agenda-skip-function
 Search for entries with a limit set on levels for the custom search.
 This is a general approach to creating custom searches in Org.  To
-include all levels, use =LEVEL>0=[fn:160].  Then to selectively pick
+include all levels, use =LEVEL>0=[fn:161].  Then to selectively pick
 the matched entries, use ~org-agenda-skip-function~, which also
 accepts Lisp forms, such as ~org-agenda-skip-entry-if~ and
 ~org-agenda-skip-subtree-if~.  For example:
@@ -21744,64 +21744,68 @@ to remove code evaluation from the {{{kbd(C-c C-c)}}} key binding.
 are not evaluated when they appear in a keyword (see [[*Summary of
 In-Buffer Settings]]).
 
-[fn:142] C++ language is handled in =ob-C.el=.  Even though the
+[fn:142] For shell source blocks, the default is to return the output.
+If you want to enforce returning the exit status, add =:results value=
+explicitely.
+
+[fn:143] C++ language is handled in =ob-C.el=.  Even though the
 identifier for such source blocks is =C++=, you activate it by loading
 the C language.
 
-[fn:143] D language is handled in =ob-C.el=.  Even though the
+[fn:144] D language is handled in =ob-C.el=.  Even though the
 identifier for such source blocks is =D=, you activate it by loading
 the C language.
 
-[fn:144] For Noweb literate programming details, see
+[fn:145] For Noweb literate programming details, see
 http://www.cs.tufts.edu/~nr/noweb/.
 
-[fn:145] For more information, please refer to the commentary section
+[fn:146] For more information, please refer to the commentary section
 in =org-tempo.el=.
 
-[fn:146] Org Indent mode also sets ~wrap-prefix~ correctly for
+[fn:147] Org Indent mode also sets ~wrap-prefix~ correctly for
 indenting and wrapping long lines of headlines or text.  This minor
 mode also handles Visual Line mode and directly applied settings
 through ~word-wrap~.
 
-[fn:147] This works, but requires extra effort.  Org Indent mode is
+[fn:148] This works, but requires extra effort.  Org Indent mode is
 more convenient for most applications.
 
-[fn:148] ~org-adapt-indentation~ can also be set to ='headline-data=,
+[fn:149] ~org-adapt-indentation~ can also be set to ='headline-data=,
 in which case only data lines below the headline will be indented.
 
-[fn:149] Note that Org Indent mode also sets the ~wrap-prefix~
+[fn:150] Note that Org Indent mode also sets the ~wrap-prefix~
 property, such that Visual Line mode (or purely setting ~word-wrap~)
 wraps long lines, including headlines, correctly indented.
 
-[fn:150] For a server to host files, consider using a WebDAV server,
+[fn:151] For a server to host files, consider using a WebDAV server,
 such as [[https://nextcloud.com][Nextcloud]].  Additional help is at this [[https://orgmode.org/worg/org-faq.html#mobileorg_webdav][FAQ entry]].
 
-[fn:151] If Emacs is configured for safe storing of passwords, then
+[fn:152] If Emacs is configured for safe storing of passwords, then
 configure the variable ~org-mobile-encryption-password~; please read
 the docstring of that variable.
 
-[fn:152] Symbolic links in ~org-directory~ need to have the same name
+[fn:153] Symbolic links in ~org-directory~ need to have the same name
 as their targets.
 
-[fn:153] While creating the agendas, Org mode forces =ID= properties
+[fn:154] While creating the agendas, Org mode forces =ID= properties
 on all referenced entries, so that these entries can be uniquely
 identified if Org Mobile flags them for further action.  To avoid
 setting properties configure the variable
 ~org-mobile-force-id-on-agenda-items~ to ~nil~.  Org mode then relies
 on outline paths, assuming they are unique.
 
-[fn:154] Checksums are stored automatically in the file
+[fn:155] Checksums are stored automatically in the file
 =checksums.dat=.
 
-[fn:155] The file will be empty after this operation.
+[fn:156] The file will be empty after this operation.
 
-[fn:156] https://www.ctan.org/pkg/comment
+[fn:157] https://www.ctan.org/pkg/comment
 
-[fn:157] By default this works only for LaTeX, HTML, and Texinfo.
+[fn:158] By default this works only for LaTeX, HTML, and Texinfo.
 Configure the variable ~orgtbl-radio-table-templates~ to install
 templates for other modes.
 
-[fn:158] If the =TBLFM= keyword contains an odd number of dollar
+[fn:159] If the =TBLFM= keyword contains an odd number of dollar
 characters, this may cause problems with Font Lock in LaTeX mode.  As
 shown in the example you can fix this by adding an extra line inside
 the =comment= environment that is used to balance the dollar
@@ -21809,9 +21813,9 @@ expressions.  If you are using AUCTeX with the font-latex library,
 a much better solution is to add the =comment= environment to the
 variable ~LaTeX-verbatim-environments~.
 
-[fn:159] The ~agenda*~ view is the same as ~agenda~ except that it
+[fn:160] The ~agenda*~ view is the same as ~agenda~ except that it
 only considers /appointments/, i.e., scheduled and deadline items that
 have a time specification =[h]h:mm= in their time-stamps.
 
-[fn:160] Note that, for ~org-odd-levels-only~, a level number
+[fn:161] Note that, for ~org-odd-levels-only~, a level number
 corresponds to order in the hierarchy, not to the number of stars.

etc/ORG-NEWS

@@ -251,17 +251,6 @@ and headings will be visually numeroted.
 You can turn this on/off on a per-file basis with =#+startup: num= or
 =#+startup: nonum=.
 
-*** New option ~org-babel-shell-return-value-is-exit-status~
-
-When set to =t=, consider the return value of a shell source code
-block is the exit status of its last command.  
-
-The default for this option is =nil=, i.e. the return value of a shell
-block is the output of the commands.
-
-You can turn this on individual blocks by setting the header argument
-=:value-is-exit-status= to =t=.
-
 ** Removed or renamed functions and variables
 
 *** Renamed ~org-columns-set-tags-or-toggle~
@@ -323,6 +312,7 @@ Org refile variables and functions have been moved to a new file.
 This bug [[https://lists.gnu.org/archive/html/emacs-orgmode/2013-08/msg00072.html][originally reported]] by Matt Lundin and investigated by Andrew
 Hyatt has been fixed.  Thanks to both of them.
 
+
 * Version 9.3
 
 ** Incompatible changes

lisp/ob-shell.el

@@ -71,16 +71,6 @@ outside the Customize interface."
 	 (set-default symbol value)
 	 (org-babel-shell-initialize)))
 
-(defcustom org-babel-shell-return-value-is-exit-status nil
-  "Should we consider the shell exit status as the return value?
-When this is set to nil (the default), consider that the return
-value of a shell source block is the output of the commands.
-Otherwise, consider the return value to be the exit status of the
-last command of the block."
-  :group 'org-babel
-  :type 'boolean
-  :package-version '(Org . "9.4"))
-
 (defun org-babel-execute:shell (body params)
   "Execute a block of Shell commands with Babel.
 This function is called by `org-babel-execute-src-block'."
@@ -89,8 +79,8 @@ This function is called by `org-babel-execute-src-block'."
 	 (stdin (let ((stdin (cdr (assq :stdin params))))
                   (when stdin (org-babel-sh-var-to-string
                                (org-babel-ref-resolve stdin)))))
-	 (value-is-exit-status (or (cdr (assq :value-is-exit-status params))
-				   org-babel-shell-return-value-is-exit-status))
+	 (value-is-exit-status
+	  (member "value" (cdr (assq :result-params params))))
 	 (cmdline (cdr (assq :cmdline params)))
          (full-body (concat
 		     (org-babel-expand-body:generic
@@ -223,8 +213,8 @@ If RESULT-TYPE equals `output' then return a list of the outputs
 of the statements in BODY, if RESULT-TYPE equals `value' then
 return the value of the last statement in BODY."
   (let* ((shebang (cdr (assq :shebang params)))
-	 (value-is-exit-status (or (cdr (assq :value-is-exit-status params))
-				   org-babel-shell-return-value-is-exit-status))
+	 (value-is-exit-status
+	  (member "value" (cdr (assq :result-params params))))
 	 (results
 	  (cond
 	   ((or stdin cmdline)	       ; external shell script w/STDIN