From 90617e2bfb73e40e04dc83fa526538be96dcd9ff Mon Sep 17 00:00:00 2001
From: Matthew Butterick <mb@mbtype.com>
Date: Thu, 28 Jan 2016 18:39:44 -0800
Subject: [PATCH] add `when/splice/text`

---
 pollen/core.rkt           | 29 ++++++++++++++++++-----------
 pollen/private/splice.rkt | 11 +++++++----
 2 files changed, 25 insertions(+), 15 deletions(-)

diff --git a/pollen/core.rkt b/pollen/core.rkt
index dfa3a94..ac1c53b 100644
--- a/pollen/core.rkt
+++ b/pollen/core.rkt
@@ -1,11 +1,13 @@
 #lang racket/base
-(require (for-syntax racket/base "world.rkt"))
+(require (for-syntax racket/base "world.rkt" "private/splice.rkt"))
 (require txexpr xml/path sugar/define sugar/coerce sugar/test racket/string)
 (require "private/file-utils.rkt"
          "world.rkt"
          "cache.rkt"
          "pagetree.rkt"
-         "private/to-string.rkt")
+         "tag.rkt"
+         "private/to-string.rkt"
+         "private/splice.rkt")
 
 (define is-meta-value? hash?)
 (define is-doc-value? txexpr?)
@@ -13,7 +15,7 @@
 (define not-false? identity)
 
 (define+provide define-meta identity) ;; stub so it will be picked up for docs
-
+(define+provide @ (make-default-tag-function '@))
 
 (define+provide/contract (select* key value-source)
   (coerce/symbol? (or/c is-meta-value? is-doc-value? pagenode? pathish?) . -> . (or/c #f txexpr-elements?))
@@ -108,17 +110,22 @@
     [(_ COND BODY ...)
      (with-syntax ([SPLICING-TAG (datum->syntax stx (world:current-splicing-tag))])
        #'(if COND
-             (with-handlers ([exn:fail? (λ(exn) (error (format "within when/block, ~a" (exn-message exn))))])
+             (with-handlers ([exn:fail? (λ(exn) (error (format "within when/splice, ~a" (exn-message exn))))])
                (list 'SPLICING-TAG BODY ...)) 
              ""))]))
 
-(provide when/block) ; bw compat
-(define-syntax (when/block stx)
+
+(provide when/splice/text)
+(define-syntax (when/splice/text stx)
   (syntax-case stx ()
-    [(_ condition body ...)
-     #'(if condition (string-append* 
-                      (with-handlers ([exn:fail? (λ(exn) (error (format "within when/block, ~a" (exn-message exn))))])
-                        (map to-string (list body ...)))) 
-           "")]))
+    [(_ COND BODY ...)
+     (with-syntax ([SPLICING-TAG (datum->syntax stx (world:current-splicing-tag))])
+       #'(if COND
+             (with-handlers ([exn:fail? (λ(exn) (error (format "within when/splice, ~a" (exn-message exn))))])
+               (map to-string (list BODY ...))) 
+             ""))]))
 
 
+(provide when/block) ; bw compat
+(define-syntax-rule (when/block cond body ...)
+  (when/splice/text cond body ...))
diff --git a/pollen/private/splice.rkt b/pollen/private/splice.rkt
index b6dc9c0..e0877a7 100644
--- a/pollen/private/splice.rkt
+++ b/pollen/private/splice.rkt
@@ -1,7 +1,10 @@
 #lang racket/base
 (provide (all-defined-out))
 
-(define (splice x [splicing-tag '@])
+;; (string->symbol (format "~a" #\u200B))
+(define splice-signal-tag '@)
+
+(define (splice x [splicing-tag splice-signal-tag])
   ;  (listof txexpr-elements?) . -> . (listof txexpr-elements?))
   (define spliceable? (λ(x) (and (pair? x) (eq? (car x) splicing-tag))))
   (define not-null-string? (λ(x) (not (and (string? x) (= (string-length x) 0)))))
@@ -14,9 +17,9 @@
 
 (module+ test
   (require rackunit)
-  (check-equal? (splice '((div 1 (@ 2 "" (@ 3 (div 4 (@ 5))) 6) "" 7)))
+  (check-equal? (splice `((div 1 (,splice-signal-tag 2 "" (,splice-signal-tag 3 (div 4 (,splice-signal-tag 5))) 6) "" 7)))
                 '((div 1 2 3 (div 4 5) 6 7)))
-  (check-equal? (splice '((@ 1 (@ 2 "" (@ 3 (div 4 (@ 5))) 6) "" 7)))
+  (check-equal? (splice `((,splice-signal-tag 1 (,splice-signal-tag 2 "" (,splice-signal-tag 3 (div 4 (,splice-signal-tag 5))) 6) "" 7)))
                 '(1 2 3 (div 4 5) 6 7))
-  (check-equal? (splice '((@ "foo" "" "bar"))) '("foo" "bar"))
+  (check-equal? (splice `((,splice-signal-tag "foo" "" "bar"))) '("foo" "bar"))
   (check-equal? (splice null) null))
\ No newline at end of file