Fix (htm ...) output resetting indentation to zero.

This is an issue present in the original Common Lisp
implementation. When the (htm ...) inner macros are
being expanded, they are not receiving the *indent*
level.

We address this by adding yet another unreleased feature
to TXR Lisp that will appear in TXR 287: expander-let.

* who.tl (tree-to-template): Here, instead of generating
a ^(let ((*indent* , *indent*)) ...) which does nothing,
we use expander-let. All the expansion of the structured
code to HTML text fragments happens at macro-expansion
time. But macro-expansion time will not execute a binding
form like (let ((*indent* <value>)) ...). It will just
expand it! The (htm ...) subforms get expanded in a
context in which all the functions that expanded the outer
macro have already terminated and undone their own
local binding of *indent*. The expander-let construct
causes the macro expander itself to do the binding. So
it will pick up the indentation where the previous
expansion pass left off.
(with-html-output): The previous fix isn't enough, because
the way the local html macro is defined also wrecks
indentation. htm expands to an invocation of with-html-output
which copies the :indent argument value from the surrouning
with-html-output. If that is 0 or t, it will reset the
indentation to zero. The htm macro should just leave the
indentation alone; not pass that keyword argument so that
the current *indent* value gets propagated.

1 files changed, 2 insertions, 2 deletions

diff --git a/who.tl b/who.tl
index 85f5a34..3ea8d80 100644
--- a/who.tl
+++ b/who.tl
@@ -168,7 +168,7 @@
          (ncon [process-tag element tree-to-template]))
         (@(consp)
          ;; list - insert as sexp
-         (add ^(let ((*indent* , *indent*)) ,element)))
+         (add ^(expander-let ((*indent* , *indent*)) ,element)))
         ;; something else - insert verbatim
         (@else (add else))))))
 
@@ -229,7 +229,7 @@
                             . body)
   ^(let ((,var ,(or stream var)))
      (macrolet ((htm (. body)
-                  ^(with-html-output (,',var nil :prologue nil :indent ,,indent)
+                  ^(with-html-output (,',var nil :prologue nil)
                      ,*body))
                 (fmt (. args)
                   ^(format ,',var ,*args))