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-rw-r--r--src/guile/skribilo/package/diff.scm35
1 files changed, 31 insertions, 4 deletions
diff --git a/src/guile/skribilo/package/diff.scm b/src/guile/skribilo/package/diff.scm
index 3aeed08..12eedb3 100644
--- a/src/guile/skribilo/package/diff.scm
+++ b/src/guile/skribilo/package/diff.scm
@@ -21,6 +21,7 @@
(define-module (skribilo package diff)
:use-module (differ)
:use-module (srfi srfi-1)
+ :use-module (srfi srfi-14)
:use-module (srfi srfi-39)
:use-module (ice-9 optargs)
@@ -197,19 +198,45 @@
;; Return a list (actually an AST) denoting the differences between STR1
;; and STR2. The returned text is actually that of STR2 augmented with
;; `insertion', `deletion', `replacement', and `unchanged' markup.
+
+ (define (space-preserving-substring str start end)
+ ;; Return the substring of STR, possibly inserting unbreakable spaces at
+ ;; the beginning/end if STR starts/ends in whitespaces.
+ (let ((len (- end start)))
+ (if (> len 0)
+ (let* ((lead (string-ref str start))
+ (lead* (if (char-set-contains? char-set:whitespace
+ lead)
+ (~)
+ (string lead))))
+ (if (> len 1)
+ (let* ((trail (string-ref str (- end 1)))
+ (trail* (if (char-set-contains? char-set:whitespace
+ trail)
+ (~)
+ (string trail))))
+ (list lead* (substring str (+ start 1) (- end 1))
+ trail*))
+ (list lead* (substring str (+ start 1) end))))
+ "")))
+
(reverse!
(fold (lambda (edit result)
(let ((start (cadr edit))
(end (+ 1 (caddr edit))))
(cons (case (car edit)
((insertion)
- (insertion (substring str2 start end)))
+ (insertion (space-preserving-substring str2 start
+ end)))
((deletion)
- (deletion (substring str1 start end)))
+ (deletion (space-preserving-substring str1 start
+ end)))
((replacement)
- (replacement (substring str2 start end)))
+ (replacement (space-preserving-substring str2 start
+ end)))
((unchanged)
- (unchanged (substring str2 start end))))
+ (unchanged (space-preserving-substring str2 start
+ end))))
result)))
'()
(string-diff-sequences str1 str2))))