From 91a6a956980eef1dc12720f716c5ca64acc503f6 Mon Sep 17 00:00:00 2001
From: Matthew Butterick <mb@mbtype.com>
Date: Wed, 29 May 2019 13:58:06 -0700
Subject: [PATCH] support expressions in meta values

---
 pollen/private/main-base.rkt   |  6 ++++--
 pollen/private/split-metas.rkt | 31 ++++++++++++++++---------------
 2 files changed, 20 insertions(+), 17 deletions(-)

diff --git a/pollen/private/main-base.rkt b/pollen/private/main-base.rkt
index ba34524..cd06c3d 100644
--- a/pollen/private/main-base.rkt
+++ b/pollen/private/main-base.rkt
@@ -36,7 +36,7 @@
   (syntax-case stx ()
     [(_ PARSER-MODE . EXPRS)
      (with-syntax ([EXPRS (replace-context #'here #'EXPRS)]
-                   [META-HASH (split-metas #'EXPRS (setup:define-meta-name))]
+                   [((META-KEY . META-VAL) ...) (split-metas #'EXPRS (setup:define-meta-name))]
                    [METAS-ID (setup:meta-export)]
                    [META-MOD-ID (setup:meta-export)]
                    [ROOT-ID (setup:main-root-node)]
@@ -51,7 +51,9 @@
               (proc doc-elements))) ;  positional arg for doclang-raw: post-processor
           (module META-MOD-ID racket/base
             (provide METAS-ID)
-            (define METAS-ID META-HASH))
+            (define METAS-ID (for/hasheq ([k (in-list (list 'META-KEY ...))]
+                                          [v (in-list (list META-VAL ...))])
+                               (values k v))))
           (require pollen/top pollen/core pollen/setup (submod "." META-MOD-ID))
           (provide (all-defined-out) METAS-ID DOC-ID)
           (define prev-metas (current-metas))
diff --git a/pollen/private/split-metas.rkt b/pollen/private/split-metas.rkt
index a77ed4b..ef27bfd 100644
--- a/pollen/private/split-metas.rkt
+++ b/pollen/private/split-metas.rkt
@@ -4,22 +4,23 @@
 (provide (all-defined-out))
 
 (define (split-metas x [meta-key 'define-meta])
-  (apply hasheq
-         (let loop ([x ((if (syntax? x) syntax->datum values) x)])
-           (match x
-             [(list (== meta-key eq?) key val)
-              (unless (symbol? key)
-                (raise-argument-error meta-key "valid meta key" key))
-              (list key val)]
-             [(? list? xs) (append-map loop xs)]
-             [_ null]))))
+  (let loop ([x ((if (syntax? x) syntax->datum values) x)])
+    (match x
+      [(list (== meta-key eq?) key)
+       (raise-argument-error meta-key "meta value missing" key)]
+      [(list (== meta-key eq?) key val)
+       (unless (symbol? key)
+         (raise-argument-error meta-key "valid meta key" key))
+       (list (cons key val))]
+      [(? list? xs) (append-map loop xs)]
+      [_ null])))
 
 (module+ test
   (require rackunit)
-  (check-equal? (split-metas 'root) (hasheq))
-  (check-equal? (split-metas '(root)) (hasheq))
+  (check-equal? (split-metas 'root) null)
+  (check-equal? (split-metas '(root)) null)
   (check-exn exn:fail:contract? (λ () (split-metas '(root (define-meta 42 "bar")))))
-  (check-equal? (split-metas '(root (div #:kw #f (define-meta foo "bar") "hi") "zim" (define-meta foo "boing") "zam")) '#hasheq((foo . "boing")))
-  (check-equal? (split-metas '(root (div #:kw #f (define-meta foo 'bar) "hi") "zim" (define-meta foo 'boing) "zam")) '#hasheq((foo . 'boing)))
-  (check-equal? (split-metas #'(root (define-meta dog "Roxy") (define-meta dog "Lex"))) '#hasheq((dog . "Lex")))
-  (check-equal? (split-metas #'(root (define-meta dog "Roxy") (div (define-meta dog "Lex")))) '#hasheq((dog . "Lex"))))
\ No newline at end of file
+  (check-equal? (split-metas '(root (div #:kw #f (define-meta foo "bar") "hi") "zim" (define-meta foo "boing") "zam")) '((foo . "bar") (foo . "boing")))
+  (check-equal? (split-metas '(root (div #:kw #f (define-meta foo 'bar) "hi") "zim" (define-meta foo 'boing) "zam")) '((foo . 'bar) (foo . 'boing)))
+  (check-equal? (split-metas #'(root (define-meta dog "Roxy") (define-meta dog "Lex"))) '((dog . "Roxy") (dog . "Lex")))
+  (check-equal? (split-metas #'(root (define-meta dog "Roxy") (div (define-meta dog "Lex")))) '((dog . "Roxy") (dog . "Lex"))))
\ No newline at end of file