From 5b942166f50034b4ff134e8d93dc3d16243791d7 Mon Sep 17 00:00:00 2001
From: David Florness <david@florness.com>
Date: Sat, 7 Mar 2020 13:32:04 -0700
Subject: [PATCH] Repl errors should not kill the bulletin

---
 bulletin.rkt | 96 +++++++++++++++++++++++++++-------------------------
 1 file changed, 50 insertions(+), 46 deletions(-)

diff --git a/bulletin.rkt b/bulletin.rkt
index 7c8a4f9..9d05013 100644
--- a/bulletin.rkt
+++ b/bulletin.rkt
@@ -194,49 +194,53 @@
   (let loop ()
     (let ([line (readline "> ")])
       (when (not (eq? line eof))
-        (let ([sp (open-input-string line)])
-          (match (read sp)
-            ['add (match (read sp)
-                    ['cand
-                     (let* ([cand (read sp)]
-                            [cand (if (symbol? cand)
-                                      (symbol->string cand)
-                                      cand)])
-                       (hash-update! election->candidates
-                                     election
-                                     (λ (l)
-                                       (cons cand l))))]
-                    [else (displayln "cannot add that")])]
-            ['list (match (read sp)
-                     ['cands
-                      (displayln (hash-ref election->candidates election))]
-                     ['peers
-                      (displayln _peers)])]
-            ['set (match (read sp)
-                    ['election (let ([election (read sp)])
-                                 (election-set! election))]
-                    [else (displayln "cannot set that")])]
-            ['open
-             (if (memq state '(closed registering))
-                 (transition 'committing)
-                 (displayln "election is not closed"))]
-            ['close
-             (transition 'closed)
-             (reset)]
-            ['register
-             (transition 'registering)
-             (reset)]
-            ['kick (if (eq? state 'closed)
-                       (let* ([peer-uname (read sp)]
-                              [peer-uname (if (symbol? peer-uname)
-                                        (symbol->string peer-uname)
-                                        peer-uname)])
-                         (for ([peer _peers]
-                               #:when (equal? (hash-ref peer 'username)
-                                              peer-uname))
-                           (set-remove! _peers peer)))
-                       (displayln "close the election first"))]
-            [else (displayln "unknown command")])
-          (when (not (equal? line ""))
-            (add-history line))
-          (loop))))))
+        (when (not (equal? line ""))
+          (add-history line))
+        (with-handlers ([exn:fail? (λ (ex)
+                                     (displayln (exn-message ex))
+                                     (break-enabled #t)
+                                     (loop))])
+          (let ([sp (open-input-string line)])
+            (match (read sp)
+              ['add (match (read sp)
+                      ['cand
+                       (let* ([cand (read sp)]
+                              [cand (if (symbol? cand)
+                                        (symbol->string cand)
+                                        cand)])
+                         (hash-update! election->candidates
+                                       election
+                                       (λ (l)
+                                         (cons cand l))))]
+                      [else (displayln "cannot add that")])]
+              ['list (match (read sp)
+                       ['cands
+                        (displayln (hash-ref election->candidates election))]
+                       ['peers
+                        (displayln _peers)])]
+              ['set (match (read sp)
+                      ['election (let ([election (read sp)])
+                                   (election-set! election))]
+                      [else (displayln "cannot set that")])]
+              ['open
+               (if (memq state '(closed registering))
+                   (transition 'committing)
+                   (displayln "election is not closed"))]
+              ['close
+               (transition 'closed)
+               (reset)]
+              ['register
+               (transition 'registering)
+               (reset)]
+              ['kick (if (eq? state 'closed)
+                         (let* ([peer-uname (read sp)]
+                                [peer-uname (if (symbol? peer-uname)
+                                                (symbol->string peer-uname)
+                                                peer-uname)])
+                           (for ([peer _peers]
+                                 #:when (equal? (hash-ref peer 'username)
+                                                peer-uname))
+                             (set-remove! _peers peer)))
+                         (displayln "close the election first"))]
+              [else (displayln "unknown command")])
+            (loop)))))))
-- 
2.38.4