document & test `trim-whitespace?`

pollen/private/ts.rktd

@@ -1 +1 @@
-1537996006
+1540870700

pollen/scribblings/setup.scrbl

@@ -149,7 +149,9 @@ If the cache can't find a certain file on the watchlist, it will be ignored. The
 
 @defoverridable[index-pages (listof string?)]{List of strings that the project server will use as directory default pages, in order of priority. Has no effect on command-line rendering operations. Also has no effect on your live web server (usually  that's a setting you need to make in an @tt{.htaccess} configuration file).} But with this setting, you can simulate the behavior of your live server, so that internal index-page URLs work correctly.
 
+ @defoverridable[trim-whitespace? boolean?)]{Predicate that controls whether the Pollen source reader trims whitespace from the beginning of a @racket[doc] export. You might set this to @racket[#false] if you're using Pollen as a preprocessor for another programming language and you want to preserve leading whitespace accurately.
 
+ @pollen-history[#:added "1.5"]}
 
 
 @section{Parameters}

pollen/test/data/whitespace/pollen.rkt

@@ -0,0 +1,7 @@
+#lang racket/base
+(require pollen/setup)
+(provide (all-defined-out))
+
+(module setup racket/base
+  (provide (all-defined-out))
+  (define trim-whitespace? #false))

pollen/test/data/whitespace/whitespace-test.txt.pp

@@ -0,0 +1,10 @@
+#lang pollen
+
+
+
+
+
+
+
+
+one

pollen/test/test-trim-whitespace.rkt

@@ -0,0 +1,11 @@
+#lang at-exp racket/base
+(require rackunit pollen/setup racket/runtime-path pollen/render)
+
+;; define-runtime-path only allowed at top level
+(define-runtime-path whitespace-dir "data/whitespace")
+(define-runtime-path whitespace-source "data/whitespace/whitespace-test.txt.pp")
+
+(parameterize ([current-directory whitespace-dir]
+               [current-project-root whitespace-dir]
+               [current-output-port (open-output-string)])
+  (check-equal? (render whitespace-source) "\n\n\n\n\n\n\n\n\none"))