Document HTTP rules a little better

It turns out we don't document the "port" option anywhere, so probably
worth doing a bit of an overhaul here.

 - Expand the top-level HTTP rules comment, clarifying how things are
   matched and describing each field.

 - Improve the comments on the default HTTP rule. We now also describe
   the $private rule and its motivation.

 - Don't drop/ignore invalid rules. This gets written back to the
   original config file, so is very annoying! Instead we now log an
   error and convert the rule into a "deny all" rule, which should make
   it obvious something is wrong.

projects/core/src/main/java/dan200/computercraft/core/apis/http/options/AddressPredicate.java

@@ -5,10 +5,7 @@
 package dan200.computercraft.core.apis.http.options;
 
 import com.google.common.net.InetAddresses;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 
-import javax.annotation.Nullable;
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
 import java.util.regex.Pattern;
@@ -19,8 +16,6 @@ import java.util.regex.Pattern;
  * @see AddressRule#apply(Iterable, String, InetSocketAddress) for the actual handling of this rule.
  */
 interface AddressPredicate {
-    Logger LOG = LoggerFactory.getLogger(AddressPredicate.class);
-
     default boolean matches(String domain) {
         return false;
     }
@@ -51,28 +46,25 @@ interface AddressPredicate {
             return true;
         }
 
-        @Nullable
         public static HostRange parse(String addressStr, String prefixSizeStr) {
             int prefixSize;
             try {
                 prefixSize = Integer.parseInt(prefixSizeStr);
             } catch (NumberFormatException e) {
-                LOG.error(
-                    "Malformed http whitelist/blacklist entry '{}': Cannot extract size of CIDR mask from '{}'.",
+                throw new InvalidRuleException(String.format(
+                    "Invalid host host '%s': Cannot extract size of CIDR mask from '%s'.",
                     addressStr + '/' + prefixSizeStr, prefixSizeStr
-                );
-                return null;
+                ));
             }
 
             InetAddress address;
             try {
                 address = InetAddresses.forString(addressStr);
             } catch (IllegalArgumentException e) {
-                LOG.error(
-                    "Malformed http whitelist/blacklist entry '{}': Cannot extract IP address from '{}'.",
+                throw new InvalidRuleException(String.format(
+                    "Invalid host '%s': Cannot extract IP address from '%s'.",
                     addressStr + '/' + prefixSizeStr, addressStr
-                );
-                return null;
+                ));
             }
 
             // Mask the bytes of the IP address.
@@ -112,7 +104,6 @@ interface AddressPredicate {
         }
     }
 
-
     final class PrivatePattern implements AddressPredicate {
         static final PrivatePattern INSTANCE = new PrivatePattern();
 

projects/core/src/main/java/dan200/computercraft/core/apis/http/options/AddressRule.java

@@ -35,14 +35,13 @@ public final class AddressRule {
         this.port = port;
     }
 
-    @Nullable
     public static AddressRule parse(String filter, OptionalInt port, PartialOptions partial) {
         var cidr = filter.indexOf('/');
         if (cidr >= 0) {
             var addressStr = filter.substring(0, cidr);
             var prefixSizeStr = filter.substring(cidr + 1);
             var range = HostRange.parse(addressStr, prefixSizeStr);
-            return range == null ? null : new AddressRule(range, port, partial);
+            return new AddressRule(range, port, partial);
         } else if (filter.equalsIgnoreCase("$private")) {
             return new AddressRule(PrivatePattern.INSTANCE, port, partial);
         } else {

projects/core/src/main/java/dan200/computercraft/core/apis/http/options/InvalidRuleException.java

@@ -0,0 +1,23 @@
+// SPDX-FileCopyrightText: 2023 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.core.apis.http.options;
+
+import java.io.Serial;
+import java.util.OptionalInt;
+
+/**
+ * Throw when a {@link AddressRule} cannot be parsed.
+ *
+ * @see AddressRule#parse(String, OptionalInt, PartialOptions)
+ * @see AddressPredicate.HostRange#parse(String, String)
+ */
+public class InvalidRuleException extends RuntimeException {
+    @Serial
+    private static final long serialVersionUID = 1303376302865132758L;
+
+    public InvalidRuleException(String message) {
+        super(message);
+    }
+}

projects/core/src/main/resources/data/computercraft/lua/rom/programs/lua.lua

@@ -90,9 +90,8 @@ while running do
 
         local results = table.pack(exception.try(func))
         if results[1] then
-            local n = 1
-            while n < results.n do
-                local value = results[n + 1]
+            for i = 2, results.n do
+                local value = results[i]
                 local ok, serialised = pcall(pretty.pretty, value, {
                     function_args = settings.get("lua.function_args"),
                     function_source = settings.get("lua.function_source"),
@@ -102,7 +101,6 @@ while running do
                 else
                     print(tostring(value))
                 end
-                n = n + 1
             end
         else
             printError(results[2])