regsub: Fix regsub -all with \A

regsub -all matches \A against the start of each match, but
correctly handle a pattern like ^ which does not advance the
match

Signed-off-by: Steve Bennett <steveb@workware.net.au>

3 files changed, 18 insertions, 11 deletions

diff --git a/jim-regexp.c b/jim-regexp.c
index b0411f8..880bf33 100644
--- a/jim-regexp.c
+++ b/jim-regexp.c
@@ -540,7 +540,14 @@ int Jim_RegsubCmd(Jim_Interp *interp, int argc, Jim_Obj *const *argv)
             n--;
         }
 
-        regexec_flags |= REG_NOTBOL;
+        if (pmatch[0].rm_eo == pmatch[0].rm_so) {
+            /* The match did not advance the string, so set REG_NOTBOL to force the next match */
+            regexec_flags = REG_NOTBOL;
+        }
+        else {
+            regexec_flags = 0;
+        }
+
     } while (n);
 
     /*
diff --git a/jim_tcl.txt b/jim_tcl.txt
index 159dea9..0ba2e5b 100644
--- a/jim_tcl.txt
+++ b/jim_tcl.txt
@@ -61,6 +61,7 @@ Changes between 0.78 and 0.79
 5. Add support for `file split`
 6. Add support for `json::encode` and `json::decode`
 7. `aio tty` now allows setting +echo+ without full +raw+ mode
+8. `regsub` now fully supports +{backslash}A+
 
 Changes between 0.77 and 0.78
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -1088,12 +1089,11 @@ and POSIX are highlighted below.
 2. All Tcl character classes are supported (e.g. +[:alnum:]+, +[:digit:]+, +[:space:]+), but...
 3. Character classes apply to ASCII characters only
 4. Supported shorthand character classes: +{backslash}w+ = +[:alnum:]+, +{backslash}W+ = +^[:alnum:]+, +{backslash}d+ = +[:digit:],+ +{backslash}D+ = +^[:digit:],+ +{backslash}s+ = +[:space:]+, + +{backslash}S+ = +^[:space:]+
-5. Supported constraint escapes: +{backslash}m+ = +{backslash}<+ = start of word, +{backslash}M+ = +{backslash}>+ = end of word
+5. Supported constraint escapes: +{backslash}m+ = +{backslash}<+ = start of word, +{backslash}M+ = +{backslash}>+ = end of word, +{backslash}A+ = start of string, +{backslash}Z+ = end of string
 6. Backslash escapes may be used within regular expressions, such as +{backslash}n+ = newline, +{backslash}uNNNN+ = unicode
-7. Partially supported constraint escapes: +{backslash}A+ = start of string, +{backslash}Z+ = end of string
-8. Support for the +?+ non-greedy quantifier. e.g. +*?+
-9. Support for non-capturing parentheses +(?:...)+
-10. Jim Tcl considers that both patterns and strings end at a null character (+\x00+)
+7. Support for the +?+ non-greedy quantifier. e.g. +*?+
+8. Support for non-capturing parentheses +(?:...)+
+9. Jim Tcl considers that both patterns and strings end at a null character (+\x00+)
 
 STRING MATCHING
 ---------------
diff --git a/tests/regexp.test b/tests/regexp.test
index c6133e7..45eddbb 100644
--- a/tests/regexp.test
+++ b/tests/regexp.test
@@ -489,11 +489,11 @@ test regexp-16.3 {regsub -start} {
     catch {unset x}
     list [regsub -all -start 3 {z} hello {/&} x] $x
 } {0 hello}
-#test regexp-16.4 {regsub -start, \A behavior} {
-#    set out {}
-#    lappend out [regsub -start 0 -all {\A(\w)} {abcde} {/\1} x] $x
-#    lappend out [regsub -start 2 -all {\A(\w)} {abcde} {/\1} x] $x
-#} {5 /a/b/c/d/e 3 ab/c/d/e}
+test regexp-16.4 {regsub -start, \A behavior} {
+    set out {}
+    lappend out [regsub -start 0 -all {\A(\w)} {abcde} {/\1} x] $x
+    lappend out [regsub -start 2 -all {\A(\w)} {abcde} {/\1} x] $x
+} {5 /a/b/c/d/e 3 ab/c/d/e}
 test regexp-16.5 {regsub -start, double option} {
     list [regsub -start 2 -start 0 a abc c x] $x
 } {1 cbc}