mediawiki-extensions-Scribunto/engines/LuaStandalone/protocol.txt
Tim Starling da06273ede Nicer errors with backtraces etc.
* Added error backtrace collection to MWServer:handleCall()
* When there is an error on parse, show a short and simple inline error
  message to the user, which when clicked, expands to a full error with
  HTML-formatted backtrace.
* When an error is encountered during module validation, have the code
  editor jump directly to the line. Requires r115011.
* Expose the code location of most errors to Scribunto, by parsing the
  standard error message format.
* During module validation, abbreviate the error location if the error
  is in the same module.
* Do not execute the module during validation, just parse it. Execution
  does not really work without an active parse operation in progress.
  It already caused a fatal error if you called require() from the main
  chunk, and problems would have become more visible as more
  parser-related APIs were added.
* LuaSandbox does not yet provide backtraces, but this is planned.

Change-Id: Id9f6564a41b310792b3fe3ebb527cbf8f8771bd1
2012-04-23 21:58:30 +10:00

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The Lua standalone engine has a message-based protocol for communicating between
PHP and Lua.
Messages start with a 16 byte header. The first 8 bytes are the body length in
hexadecimal. The second 8 bytes are (length * 2 - 1) also in hexadecimal.
For messages passed from PHP to Lua, the body is encoded as a Lua expression.
The expression may reference a table in a variable called "chunks", which
contains an array of functions.
Messages passed from Lua to PHP have their body encoded in PHP serialize() format.
They may include instances of function objects which have an "id" member for
passing back to Lua as an index in the chunk table.
The expressions encoded into the message bodies are associative arrays. The "op"
member of the array gives the operation to be performed by the message.
Every request message demands exactly one response message in reply. When a
request message is sent, the responder does not need to send the corresponding
response message as its next message. It may instead send its own request
message. In this way, a stack of pending requests can be accumulated. This
mechanism allows re-entrant and recursive calls.
All numerically-indexed arrays should start from index 1 unless otherwise
specified.
== Request messages sent from PHP to Lua ==
=== loadString ===
Load some executable Lua code (a "chunk") and return the resulting function ID.
Message parameters:
* op: "loadString"
* text: The string to load
* chunkName: The name of the string, for use in error messages
On success, the response message is:
* op: "return"
* values: An array with a single element with the ID in it
On failure, the response message is:
* op: "error"
* value: The error message
=== call ===
Call a Lua function.
Message parameters:
* op: "call"
* id: The chunk ID
* args: The argument array
On success, the response message is:
* op: "return"
* values: All return values as an array
On failure, the response message is:
* op: "error"
* value: The value given to error(), usually an error message
* trace: A table giving a backtrace of the stack as it was when error() was
called, in a similar format to the one used by debug.getinfo(). Element 1 of
the table is the function that called error(), element 2 is the function that
called that, and so on.
=== registerLibrary ===
Register a set of functions in the sandbox environment.
Message parameters:
* op: "registerLibrary"
* name: The global variable name to register. May contain "." characters to
specify a global variable subtable.
* functions: An associative array mapping function name to ID
On success, the response message is:
* op: "return"
* values: An empty array
On failure the response message is:
* op: "error"
* value: The error message
=== getStatus ===
Get status information about the Lua process.
Message parameters:
* op: "getStatus"
On success, the response message is:
* op: "return"
* values: An array with a single element, which is an associative array mapping
status key to value. The status keys are:
** pid: The process identifier
** time: The amount of user and system time spent by the process, measured in clock ticks
** vsize: The virtual memory size in bytes
** rss: The resident set size in bytes
On failure, the response message is:
* op: "return"
* values: An empty array
=== quit ===
Request graceful shutdown.
Message parameters:
* op: "quit"
No return message will be sent.
== Request messages sent from Lua to PHP ==
=== call ===
Call a PHP function.
Message parameters:
* op: "call"
* id: The function ID given by registerLibrary
* args: An array giving the function arguments
On success, the response message is:
* op: "return"
* values: All return values as an array
On failure the response message is:
* op: "error"
* value: The error message