help.home: don't flip out if an article in the recent list does not exist. Fixes problem where forgetting a vocab screws up help browser

basis/help/apropos/apropos.factor

@@ -1,4 +1,4 @@
-! Copyright (C) 2008, 2009 Slava Pestov.
+! Copyright (C) 2008, 2010 Slava Pestov.
 ! See http://factorcode.org/license.txt for BSD license.
 USING: accessors arrays assocs fry help.markup help.topics io
 kernel make math math.parser namespaces sequences sorting
@@ -19,6 +19,8 @@ TUPLE: more-completions seq ;
 
 CONSTANT: max-completions 5
 
+M: more-completions valid-article? drop t ;
+
 M: more-completions article-title
     seq>> length number>string " results" append ;
 
@@ -60,6 +62,8 @@ TUPLE: apropos search ;
 
 C: <apropos> apropos
 
+M: apropos valid-article? drop t ;
+
 M: apropos article-title
     search>> "Search results for “" "”" surround ;
 

basis/help/help.factor

@@ -1,4 +1,4 @@
-! Copyright (C) 2005, 2009 Slava Pestov.
+! Copyright (C) 2005, 2010 Slava Pestov.
 ! See http://factorcode.org/license.txt for BSD license.
 USING: accessors arrays io io.styles kernel namespaces make
 parser prettyprint sequences words words.symbol assocs
@@ -48,6 +48,8 @@ M: predicate word-help* drop \ $predicate ;
 : all-errors ( -- seq )
     all-words [ error? ] filter sort-articles ;
 
+M: word valid-article? drop t ;
+
 M: word article-name name>> ;
 
 M: word article-title

basis/help/home/home.factor

@@ -1,4 +1,4 @@
-! Copyright (C) 2009 Slava Pestov.
+! Copyright (C) 2009, 2010 Slava Pestov.
 ! See http://factorcode.org/license.txt for BSD license.
 USING: arrays compiler.units fry hashtables help.topics io
 kernel math namespaces sequences sets help.vocabs
@@ -21,7 +21,8 @@ M: apropos add-recent-where recent-searches ;
 M: object add-recent-where f ;
 
 : $recent ( element -- )
-    first get reverse [ nl ] [ 1array $pretty-link ] interleave ;
+    first get [ valid-article? ] filter <reversed>
+    [ nl ] [ 1array $pretty-link ] interleave ;
 
 : $recent-searches ( element -- )
     drop recent-searches get [ <$link> ] map $list ;

basis/help/topics/topics.factor

@@ -1,4 +1,4 @@
-! Copyright (C) 2005, 2008 Slava Pestov.
+! Copyright (C) 2005, 2010 Slava Pestov.
 ! See http://factorcode.org/license.txt for BSD license.x
 USING: accessors arrays definitions generic assocs
 io kernel namespaces make prettyprint prettyprint.sections
@@ -38,6 +38,7 @@ SYMBOL: article-xref
 
 article-xref [ H{ } clone ] initialize
 
+GENERIC: valid-article? ( topic -- ? )
 GENERIC: article-name ( topic -- string )
 GENERIC: article-title ( topic -- string )
 GENERIC: article-content ( topic -- content )
@@ -49,6 +50,7 @@ TUPLE: article title content loc ;
 : <article> ( title content -- article )
     f \ article boa ;
 
+M: article valid-article? drop t ;
 M: article article-name title>> ;
 M: article article-title title>> ;
 M: article article-content content>> ;
@@ -61,12 +63,14 @@ M: no-article summary
 : article ( name -- article )
     articles get ?at [ no-article ] unless ;
 
+M: object valid-article? articles get key? ;
 M: object article-name article article-name ;
 M: object article-title article article-title ;
 M: object article-content article article-content ;
 M: object article-parent article-xref get at ;
 M: object set-article-parent article-xref get set-at ;
 
+M: link valid-article? name>> valid-article? ;
 M: link article-name name>> article-name ;
 M: link article-title name>> article-title ;
 M: link article-content name>> article-content ;
@@ -74,6 +78,7 @@ M: link article-parent name>> article-parent ;
 M: link set-article-parent name>> set-article-parent ;
 
 ! Special case: f help
+M: f valid-article? drop t ;
 M: f article-name drop \ f article-name ;
 M: f article-title drop \ f article-title ;
 M: f article-content drop \ f article-content ;

basis/help/vocabs/vocabs.factor

@@ -1,4 +1,4 @@
-! Copyright (C) 2007, 2009 Slava Pestov.
+! Copyright (C) 2007, 2010 Slava Pestov.
 ! See http://factorcode.org/license.txt for BSD license.
 USING: accessors arrays assocs classes classes.builtin
 classes.intersection classes.mixin classes.predicate
@@ -278,6 +278,8 @@ INSTANCE: vocab topic
 
 INSTANCE: vocab-link topic
 
+M: vocab-spec valid-article? drop t ;
+
 M: vocab-spec article-title vocab-name " vocabulary" append ;
 
 M: vocab-spec article-name vocab-name ;
@@ -289,6 +291,8 @@ M: vocab-spec article-parent drop "vocab-index" ;
 
 M: vocab-tag >link ;
 
+M: vocab-tag valid-article? drop t ;
+
 M: vocab-tag article-title
     name>> "Vocabularies tagged “" "”" surround ;
 
@@ -303,6 +307,8 @@ M: vocab-tag summary article-title ;
 
 M: vocab-author >link ;
 
+M: vocab-author valid-article? drop t ;
+
 M: vocab-author article-title
     name>> "Vocabularies by " prepend ;