Add r+/w+ support to io library

projects/core/src/main/java/dan200/computercraft/core/apis/FSAPI.java

@@ -309,10 +309,10 @@ public class FSAPI implements ILuaAPI {
      * <p>
      * The {@code mode} string can be any of the following:
      * <ul>
-     * <li><strong>"r"</strong>: Read mode</li>
+     * <li><strong>"r"</strong>: Read mode.</li>
-     * <li><strong>"w"</strong>: Write mode</li>
+     * <li><strong>"w"</strong>: Write mode.</li>
-     * <li><strong>"a"</strong>: Append mode</li>
+     * <li><strong>"a"</strong>: Append mode.</li>
-     * <li><strong>"r+"</strong>: Update mode (allows reading and writing), all data is preserved</li>
+     * <li><strong>"r+"</strong>: Update mode (allows reading and writing), all data is preserved.</li>
      * <li><strong>"w+"</strong>: Update mode, all data is erased.</li>
      * </ul>
      * <p>

projects/core/src/main/resources/data/computercraft/lua/rom/apis/io.lua

@@ -365,24 +365,26 @@ end
 -- or [`nil`], plus an error message.
 --
 -- The `mode` string can be any of the following:
---  - **"r"**: Read mode
+--  - **"r"**: Read mode.
---  - **"w"**: Write mode
+--  - **"w"**: Write mode.
---  - **"a"**: Append mode
+--  - **"a"**: Append mode.
+--  - **"r+"**: Update mode (allows reading and writing), all data is preserved.
+--  - **"w+"**: Update mode, all data is erased.
 --
 -- The mode may also have a `b` at the end, which opens the file in "binary
--- mode". This allows you to read binary files, as well as seek within a file.
+-- mode". This has no impact on functionality.
 --
 -- @tparam string filename The name of the file to open.
--- @tparam[opt] string mode The mode to open the file with. This defaults to `rb`.
+-- @tparam[opt] string mode The mode to open the file with. This defaults to `r`.
 -- @treturn[1] Handle The opened file.
 -- @treturn[2] nil In case of an error.
 -- @treturn[2] string The reason the file could not be opened.
+-- @changed 1.111.0 Add support for `r+` and `w+`.
 function open(filename, mode)
     expect(1, filename, "string")
     expect(2, mode, "string", "nil")
 
-    local sMode = mode and mode:gsub("%+", "") or "r"
+    local file, err = fs.open(filename, mode or "r")
-    local file, err = fs.open(filename, sMode)
     if not file then return nil, err end
 
     return make_file(file)

projects/core/src/test/resources/test-rom/spec/apis/io_spec.lua

@@ -329,4 +329,19 @@ describe("The io library", function()
             expect(read_all(file)):eq("alo\n " .. t .. " ;end of file\n")
         end)
     end)
+
+    describe("read/write handles", function()
+        it("can read and write to a file", function()
+            write_file(file, "an example file")
+
+            local handle = io.open(file, "r+")
+            expect(handle:read(3)):eq("an ")
+
+            handle:write("exciting file")
+            expect(handle:seek("cur")):eq(16)
+
+            handle:seek("set", 0)
+            expect(handle:read("*a")):eq("an exciting file")
+        end)
+    end)
 end)