[PATCH] lisp/ob-plantuml.el: Insert results in buffer

[Joseph Turner]

Allow src block execution without ":file" header arg. When ":file" is
omitted, insert txt output in buffer below src block.

TINYCHANGE
---
 etc/ORG-NEWS        |  5 +++++
 lisp/ob-plantuml.el | 10 +++++++---
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/etc/ORG-NEWS b/etc/ORG-NEWS
index 4cda357f1..1613fdab5 100644
--- a/etc/ORG-NEWS
+++ b/etc/ORG-NEWS
@@ -295,6 +295,11 @@ files that are exported to Texinfo.
 
 =org-at-heading-p= now returns t by default on headings inside folds.
 Passing optional argument will produce the old behaviour.
+
+*** =org-babel-execute:plantuml= can output ASCII graphs in the buffer
+
+Previously, executing PlantUML src blocks required a ":file" header argument. 
Now, if that header argument is omitted, an ASCII graph will be inserted below 
the src block.
+
 ** Removed or renamed functions and variables
 *** =org-plantump-executable-args= is renamed and applies to jar as well
 
diff --git a/lisp/ob-plantuml.el b/lisp/ob-plantuml.el
index ebbcdf166..f9b41c140 100644
--- a/lisp/ob-plantuml.el
+++ b/lisp/ob-plantuml.el
@@ -109,8 +109,9 @@ If BODY does not contain @startXXX ... @endXXX clauses, 
@startuml
 (defun org-babel-execute:plantuml (body params)
   "Execute a block of plantuml code with org-babel.
 This function is called by `org-babel-execute-src-block'."
-  (let* ((out-file (or (cdr (assq :file params))
-                      (error "PlantUML requires a \":file\" header argument")))
+  (let* ((do-export (cdr (assq :file params)))
+         (out-file (or do-export
+                      (org-babel-temp-file "plantuml-" ".txt"))) ; if ":file" 
is not provided, don't export, just print ASCII results
         (cmdline (cdr (assq :cmdline params)))
         (in-file (org-babel-temp-file "plantuml-"))
         (java (or (cdr (assq :java params)) ""))
@@ -155,7 +156,10 @@ This function is called by `org-babel-execute-src-block'."
     (if (and (string= (file-name-extension out-file) "svg")
              org-babel-plantuml-svg-text-to-path)
         (org-babel-eval (format "inkscape %s -T -l %s" out-file out-file) ""))
-    nil)) ;; signal that output has already been written to file
+    (unless do-export (with-temp-buffer
+                        (insert-file-contents out-file)
+                        (buffer-substring-no-properties (point-min) 
(point-max))
+                        ))))
 
 (defun org-babel-prep-session:plantuml (_session _params)
   "Return an error because plantuml does not support sessions."
-- 
2.37.0