ccwl: Parse run arguments recursively.

Parsing run arguments recursively allows us to share code between
different pattern matchers. For example, the input matcher and
the (prefix input) matcher can share code. This will come in handy as
our pattern matchers grow more complex.

* ccwl/ccwl.scm (run-args): Parse run arguments recursively.

1 files changed, 39 insertions, 43 deletions

diff --git a/ccwl/ccwl.scm b/ccwl/ccwl.scm
index 9b5132f..d251409 100644
--- a/ccwl/ccwl.scm
+++ b/ccwl/ccwl.scm
@@ -351,49 +351,45 @@ RUN-ARGS. If such an input is not present in RUN-ARGS, return #f."
   "Return a list of run arguments specified in @var{run}
 syntax. @var{defined-input-identifiers} is the list of input
 identifiers defined in the commands."
-  (let ((ensure-input-is-defined
-         ;; Ensure that specified input is defined in #:inputs of
-         ;; command definition.
-         (lambda (input)
-           (unless (memq (syntax->datum input)
-                         defined-input-identifiers)
-             (raise-exception
-              (condition (ccwl-violation input)
-                         (formatted-message "Undefined input ~a"
-                                            (syntax->datum input))))))))
-    (append-map (lambda (x)
-                  (syntax-case x ()
-                    ;; Replace input symbol with quoted symbol.
-                    (input (identifier? #'input)
-                           (begin
-                             (ensure-input-is-defined #'input)
-                             (list #''input)))
-                    ;; Leave string as is.
-                    (string-arg (string? (syntax->datum #'string-arg))
-                                (list #'string-arg))
-                    ;; Replace prefixed input symbol with quoted symbol.
-                    ((prefix input) (and (string? (syntax->datum #'prefix))
-                                         (identifier? #'input))
-                     (begin
-                       (ensure-input-is-defined #'input)
-                       (list #''input)))
-                    ;; Flatten prefixed string arguments. They have no
-                    ;; special meaning.
-                    ((prefix string-arg) (and (string? (syntax->datum #'prefix))
-                                              (string? (syntax->datum #'string-arg)))
-                     (list #'prefix #'string-arg))
-                    ;; Prefixes that are not strings
-                    ((prefix _)
-                     (raise-exception
-                      (condition (ccwl-violation #'prefix)
-                                 (formatted-message "Invalid prefix ~a. Prefixes must be strings."
-                                                    (syntax->datum #'prefix)))))
-                    (_
-                     (raise-exception
-                      (condition (ccwl-violation x)
-                                 (formatted-message "Invalid command element ~a. Command elements must either be input identifiers or literal strings."
-                                                    (syntax->datum x)))))))
-                run)))
+  (define (syntax->run-arg x)
+    (syntax-case x ()
+      ;; Replace input symbol with quoted symbol.
+      (input (identifier? #'input)
+             ;; Ensure that specified input is defined in #:inputs of
+             ;; command definition.
+             (begin
+               (unless (memq (syntax->datum #'input)
+                             defined-input-identifiers)
+                 (raise-exception
+                  (condition (ccwl-violation #'input)
+                             (formatted-message "Undefined input ~a"
+                                                (syntax->datum #'input)))))
+               (list #''input)))
+      ;; Leave string as is.
+      (string-arg (string? (syntax->datum #'string-arg))
+                  (list #'string-arg))
+      ;; Flatten prefixed string arguments. They have no
+      ;; special meaning.
+      ((prefix string-arg) (and (string? (syntax->datum #'prefix))
+                                (string? (syntax->datum #'string-arg)))
+       (list #'prefix #'string-arg))
+      ;; Recurse on prefixed inputs.
+      ((prefix input) (string? (syntax->datum #'prefix))
+       (syntax->run-arg #'input))
+      ;; Prefixes that are not strings
+      ((prefix _)
+       (raise-exception
+        (condition (ccwl-violation #'prefix)
+                   (formatted-message "Invalid prefix ~a. Prefixes must be strings."
+                                      (syntax->datum #'prefix)))))
+      (_
+       (raise-exception
+        (condition (ccwl-violation x)
+                   (formatted-message "Invalid command element ~a. Command elements must either be input identifiers or literal strings."
+                                      (syntax->datum x)))))))
+
+  (append-map syntax->run-arg
+              run))
 
 ;; TODO: Add fine-grained syntax checking.
 (define-syntax command