improved error diagnostics of cron tab (#1406)

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@7782 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/java/hudson/scheduler/CronTab.java

@@ -23,6 +23,11 @@ public final class CronTab {
 
     int dayOfWeek;
 
+    /**
+     * Textual representation.
+     */
+    private String spec;
+
     public CronTab(String format) throws ANTLRException {
         this(format,1);
     }
@@ -35,6 +40,7 @@ public final class CronTab {
         CrontabLexer lexer = new CrontabLexer(new StringReader(format));
         lexer.setLine(line);
         CrontabParser parser = new CrontabParser(lexer);
+        spec = format;
 
         parser.startRule(this);
         if((dayOfWeek&(1<<7))!=0)
@@ -83,4 +89,34 @@ public final class CronTab {
     private String toString(String key, long bit) {
         return key+'='+Long.toHexString(bit);
     }
+
+    /**
+     * Checks if this crontab entry looks reasonable,
+     * and if not, return an warning message.
+     *
+     * <p>
+     * The point of this method is to catch syntactically correct
+     * but semantically suspicious combinations, like
+     * "* 0 * * *"
+     */
+    public String checkSanity() {
+        for( int i=0; i<5; i++ ) {
+            for( int j=LOWER_BOUNDS[i]; j<=UPPER_BOUNDS[i]; j++ ) {
+                if(!checkBits(bits[i],j)) {
+                    // this rank has a sparse entry.
+                    // if we have a sparse rank, one of them better be the left-most.
+                    if(i>0)
+                        return "Do you really mean \"every minute\" when you say \""+spec+"\"?";
+                    // once we find a sparse rank, upper ranks don't matter
+                    return null;
+                }
+            }
+        }
+
+        return null;
+    }
+
+    // lower/uppser bounds of fields
+    private static final int[] LOWER_BOUNDS = new int[] {0,0,1,0,0};
+    private static final int[] UPPER_BOUNDS = new int[] {59,23,31,12,7};
 }

core/src/main/java/hudson/scheduler/CronTabList.java

@@ -26,6 +26,23 @@ public final class CronTabList {
         return false;
     }
 
+    /**
+     * Checks if this crontab entry looks reasonable,
+     * and if not, return an warning message.
+     *
+     * <p>
+     * The point of this method is to catch syntactically correct
+     * but semantically suspicious combinations, like
+     * "* 0 * * *"
+     */
+    public String checkSanity() {
+        for (CronTab tab : tabs) {
+            String s = tab.checkSanity();
+            if(s!=null)     return s;
+        }
+        return null;
+    }
+
     public static CronTabList create(String format) throws ANTLRException {
         Vector<CronTab> r = new Vector<CronTab>();
         int lineNumber = 0;

core/src/main/java/hudson/triggers/TimerTrigger.java

@@ -59,8 +59,11 @@ public class TimerTrigger extends Trigger<BuildableItem> {
             new FormFieldValidator(req,rsp,true) {
                 protected void check() throws IOException, ServletException {
                     try {
-                        CronTabList.create(fixNull(request.getParameter("value")));
-                        ok();
+                        String msg = CronTabList.create(fixNull(request.getParameter("value"))).checkSanity();
+                        if(msg!=null)
+                            warning(msg);
+                        else
+                            ok();
                     } catch (ANTLRException e) {
                         error(e.getMessage());
                     }