From 4734fc1e40e2fac93fca59a9deb4206513ffe999 Mon Sep 17 00:00:00 2001
From: Alex Shinn <alexshinn@gmail.com>
Date: Mon, 15 Jun 2020 11:51:32 +0900
Subject: [PATCH] friendlier report for error on module files with the wrong
 name (issue #624)

---
 lib/chibi/repl.scm | 52 +++++++++++++++++++++++++++++++++++++---------
 1 file changed, 42 insertions(+), 10 deletions(-)

diff --git a/lib/chibi/repl.scm b/lib/chibi/repl.scm
index 45c9084a..82877800 100644
--- a/lib/chibi/repl.scm
+++ b/lib/chibi/repl.scm
@@ -323,17 +323,49 @@
                                  0
                                  (- (string-length mod-file) 4))
                       ".scm")))
-      (display "Searched module path " out)
-      (display (current-module-path) out)
-      (display " for " out)
-      (write mod-file out)
-      (display ".\n" out)
       (cond
-       ((find-module-file scm-file)
-        => (lambda (file)
-             (display "But found non-module-definition file " out)
-             (write file out)
-             (display ".\nNote module files must end in \".sld\".\n" out)))))
+       ((find-module-file mod-file)
+        => (lambda (path)
+             (let ((defined-mod-name
+                     (protect (exn (else #f))
+                       (let ((x (call-with-input-file path read)))
+                         (and (pair? x)
+                              (pair? (cdr x))
+                              (eq? 'define-library (car x))
+                              (cadr x))))))
+               (cond
+                ((not defined-mod-name)
+                 (display "File '" out)
+                 (display path out)
+                 (display "' does not appear to define module " out)
+                 (display mod-name out)
+                 (display ".\n" out))
+                ((equal? defined-mod-name mod-name)
+                 (display "File '" out)
+                 (display path out)
+                 (display "' failed to define module " out)
+                 (display mod-name out)
+                 (display ".\n" out))
+                (else
+                 (display "Expected file '" out)
+                 (display path out)
+                 (display "' to define module " out)
+                 (display mod-name out)
+                 (display " but found " out)
+                 (display defined-mod-name out)
+                 (display ".\n" out))))))
+       (else
+        (display "Searched module path " out)
+        (display (current-module-path) out)
+        (display " for " out)
+        (write mod-file out)
+        (display ".\n" out)
+        (cond
+         ((find-module-file scm-file)
+          => (lambda (file)
+               (display "But found non-module-definition file " out)
+               (write file out)
+               (display ".\nNote module files must end in \".sld\".\n" out)))))))
     )))
 
 (define undefined-value (if #f #f))