Fix and document make-temp-file optional text parameter

* lisp/files.el (make-temp-file): Fix initial TEXT parameter.
(files--make-magic-temp-file): Support optional TEXT parameter.
* etc/NEWS: Document it.
* doc/lispref/files.texi: Document it.
* test/lisp/auth-source-tests.el: Minor reformat.

4 files changed, 25 insertions, 17 deletions

diff --git a/doc/lispref/files.texi b/doc/lispref/files.texi
index 25f32c231ca..9359d3eaa09 100644
--- a/doc/lispref/files.texi
+++ b/doc/lispref/files.texi
@@ -2467,11 +2467,12 @@ construct a name for such a file:
 The job of @code{make-temp-file} is to prevent two different users or
 two different jobs from trying to use the exact same file name.
 
-@defun make-temp-file prefix &optional dir-flag suffix
+@defun make-temp-file prefix &optional dir-flag suffix text
 This function creates a temporary file and returns its name.  Emacs
 creates the temporary file's name by adding to @var{prefix} some
 random characters that are different in each Emacs job.  The result is
-guaranteed to be a newly created empty file.  On MS-DOS, this function
+guaranteed to be a newly created file, containing @var{text} if that's
+given as a string and empty otherwise. On MS-DOS, this function
 can truncate the @var{string} prefix to fit into the 8+3 file-name
 limits.  If @var{prefix} is a relative file name, it is expanded
 against @code{temporary-file-directory}.
@@ -2494,6 +2495,8 @@ not the directory name, of that directory.  @xref{Directory Names}.
 If @var{suffix} is non-@code{nil}, @code{make-temp-file} adds it at
 the end of the file name.
 
+If @var{text} is a string, @code{make-temp-file} inserts it in the file.
+
 To prevent conflicts among different libraries running in the same
 Emacs, each Lisp program that uses @code{make-temp-file} should have its
 own @var{prefix}.  The number added to the end of @var{prefix}
diff --git a/etc/NEWS b/etc/NEWS
index 9e86af57757..54be0fca4af 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1210,6 +1210,8 @@ propagated to file name handlers now.
 
 * Lisp Changes in Emacs 26.1
 
+** New optional argument TEXT in 'make-temp-file'.
+
 ** New function `define-symbol-prop'.
 
 +++
diff --git a/lisp/files.el b/lisp/files.el
index 4dc1238f955..af5d3ba53e1 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -1404,8 +1404,8 @@ of PREFIX, and expanding against `temporary-file-directory' if necessary),
 is guaranteed to point to a newly created file.
 You can then use `write-region' to write new data into the file.
 
-If TEXT is non-nil, it will be inserted in the new
-file. Otherwise the file will be empty.
+If TEXT is non-nil, it will be inserted in the new file. Otherwise
+the file will be empty.
 
 If DIR-FLAG is non-nil, create a new empty directory instead of a file.
 
@@ -1413,20 +1413,25 @@ If SUFFIX is non-nil, add that at the end of the file name."
   (let ((absolute-prefix
          (if (or (zerop (length prefix)) (member prefix '("." "..")))
              (concat (file-name-as-directory temporary-file-directory) prefix)
-           (expand-file-name prefix temporary-file-directory))))
+           (expand-file-name prefix temporary-file-directory)))
+        (contents (if (stringp text) text "")))
     (if (find-file-name-handler absolute-prefix 'write-region)
-        (files--make-magic-temp-file absolute-prefix dir-flag suffix)
-      (make-temp-file-internal absolute-prefix
-                               (if dir-flag t) (or suffix "")))))
-
-(defun files--make-magic-temp-file (absolute-prefix &optional dir-flag suffix)
-  "Implement (make-temp-file ABSOLUTE-PREFIX DIR-FLAG SUFFIX).
+        (files--make-magic-temp-file absolute-prefix dir-flag suffix contents)
+      (let ((file (make-temp-file-internal absolute-prefix
+                                           (if dir-flag t) (or suffix ""))))
+        (write-region contents nil file nil 'silent)
+        file))))
+
+(defun files--make-magic-temp-file (absolute-prefix
+                                    &optional dir-flag suffix text)
+  "Implement (make-temp-file ABSOLUTE-PREFIX DIR-FLAG SUFFIX TEXT).
 This implementation works on magic file names."
   ;; Create temp files with strict access rights.  It's easy to
   ;; loosen them later, whereas it's impossible to close the
   ;; time-window of loose permissions otherwise.
   (with-file-modes ?\700
-    (let (file)
+    (let ((contents (if (stringp text) text ""))
+          file)
       (while (condition-case ()
                  (progn
                    (setq file (make-temp-name absolute-prefix))
@@ -1434,7 +1439,7 @@ This implementation works on magic file names."
                        (setq file (concat file suffix)))
                    (if dir-flag
                        (make-directory file)
-                     (write-region (or text "") nil file nil 'silent nil 'excl))
+                     (write-region contents nil file nil 'silent nil 'excl))
                    nil)
                (file-already-exists t))
         ;; the file was somehow created by someone else between
diff --git a/test/lisp/auth-source-tests.el b/test/lisp/auth-source-tests.el
index f35c4009535..90a4475ab0d 100644
--- a/test/lisp/auth-source-tests.el
+++ b/test/lisp/auth-source-tests.el
@@ -267,10 +267,8 @@
                    :host "b1" :port "b2" :user "b3")
                   ))
 
-         (netrc-file (make-temp-file
-                      "auth-source-test"
-                      nil nil
-                      (mapconcat 'identity entries "\n")))
+         (netrc-file (make-temp-file "auth-source-test" nil nil
+                                     (mapconcat 'identity entries "\n")))
          (auth-sources (list netrc-file))
          (auth-source-do-cache nil)
          found found-as-string)