Formspec AST

This mod provides an API for other mods and is useless by itself.

API

• formspec_ast.parse(formspec_string): Parses formspec_string and returns an AST.
• formspec_ast.unparse(tree): Unparses the abstract syntax tree provided and returns a formspec string.
• formspec_ast.interpret(string_or_tree): Returns a formspec string after (optionally parsing) and unparsing the formspec provided.
• formspec_ast.walk(tree): Returns an iterator (use this directly in a for loop) that will return all nodes in a tree, including ones inside containers.
• formspec_ast.find(tree, node_type): Similar to walk(tree), however only returns node_type nodes.
• formspec_ast.get_element_by_name(tree, name): Returns the first element in the tree with the name name.
• formspec_ast.get_elements_by_name(tree, name): Returns a list of all the elements with the name name.
• formspec_ast.apply_offset(tree, x, y): Shifts all elements in tree. Similar to container.
• formspec_ast.flatten(tree): Removes all containers and offsets elements that were in containers accordingly. Note that scroll_container[] elements are not flattened.
• formspec_ast.show_formspec(player_or_name, formname, formspec): Similar to minetest.show_formspec, however also accepts player objects and will pass formspec through formspec_ast.interpret first.
• formspec_ast.safe_parse(string_or_tree): Similar to formspec_ast.parse, however will delete any elements that may crash the client (or any I haven't added to the safe element list). The safe element list that this function uses is very limited, it may break complex formspecs.
• formspec_ast.safe_interpret(string_or_tree): Equivalent to formspec_ast.unparse(formspec_ast.safe_parse(string_or_tree)).
• formspec_ast.formspec_escape(text): The same as minetest.formspec_escape, should only be used when formspec_ast is being embedded outside of Minetest.

AST

The AST is similar (and generated from) the formspec element list, however all attributes are lowercase.

Recent backwards incompatibilities

While I try to reduce backwards incompatibilities, sometimes they are necessary to either fix bugs in formspec_ast or for implementing new formspec features.

April 2023

• The current_tab value of tabheader elements is now parsed as a number.

February 2022

• The value of scrollbars is now a number instead of a string.
• The item, listelem, and caption fields are now items, listelems, and captions. The old names still work when unparsing formspecs for now but are no longer used when parsing formspecs.

March 2021

• The index_event value for dropdown is now a boolean instead of a string.

February 2021

• The close_on_enter value for field_close_on_enter is now a boolean instead of a string.
• The frame_count, frame_duration and frame_start values in animated_image are now numbers.

September 2020

• The style[] element has a selectors field instead of name. Using name when unparsing formspecs still works, however parsed formspecs always use selectors.

Special cases

• formspec_version (provided it is the first element) is moved to tree.formspec_version (1 by default).

formspec_ast.parse example

Note that the whitespace in the formspec is optional and exists for readability. Non-numeric table items in the dump() output are re-ordered for readability.

> tree = formspec_ast.parse('size[5,2] '
>>     .. 'style[name;bgcolor=blue;textcolor=yellow]'
>>     .. 'container[1,1]'
>>     .. '    label[0,0;Containers are fun]'
>>     .. '    container[-1,-1]'
>>     .. '        button[0.5,0;4,1;name;Label]'
>>     .. '    container_end[]'
>>     .. '    label[0,1;Nested containers work too.]'
>>     .. 'container_end[]'
>>     .. ' image[0,1;1,1;air.png]')
> print(dump(tree))
{
    formspec_version = 1,
    {
        type = "size",
        w = 5,
        h = 2,
    },
    {
        type = "style",
        selectors = {"name"},
        props = {
            bgcolor = "blue",
            textcolor = "yellow",
        },
    },
    {
        type = "container",
        x = 1,
        y = 1,
        {
            type = "label",
            x = 0,
            y = 0,
            label = "Containers are fun",
        },
        {
            type = "container",
            x = -1,
            y = -1,
            {
                type = "button",
                x = 0.5,
                y = 0,
                w = 4,
                h = 1,
                name = "name",
                label = "Label",
            },
        },
        {
            type = "label",
            x = 0,
            y = 1,
            label = "Nested containers work too.",
        },
    },
    {
        type = "image",
        x = 0,
        y = 1,
        w = 1,
        h = 1,
        texture_name = "air.png",
    },
}

formspec_ast.flatten example

> print(dump(formspec_ast.flatten(tree)))
{
    formspec_version = 1,
    {
        type = "size",
        w = 5,
        h = 2,
    },
    {
        type = "style",
        selectors = {"name"},
        props = {
            bgcolor = "blue",
            textcolor = "yellow",
        },
    },
    {
        type = "label",
        x = 1,
        y = 1,
        label = "Containers are fun",
    },
    {
        type = "button",
        x = 0.5,
        y = 0,
        w = 4
        h = 1,
        name = "name",
        label = "Label",
    },
    {
        type = "label",
        x = 1,
        y = 2,
        label = "Nested containers work too.",
    },
    {
        type = "image",
        x = 0,
        y = 1,
        w = 1,
        h = 1,
        texture_name = "air.png",
    },
}

formspec_ast.unparse example

> print(formspec_ast.unparse(tree))
size[5,2,]style[name;textcolor=yellow;bgcolor=blue]container[1,1]label[0,0;Containers are fun]container[-1,-1]button[0.5,0;4,1;name;Label]container_end[]label[0,1;Nested containers work too.]container_end[]image[0,1;1,1;air.png]

> print(formspec_ast.unparse(formspec_ast.flatten(tree)))
size[5,2,]style[name;textcolor=yellow;bgcolor=blue]label[1,1;Containers are fun]button[0.5,0;4,1;name;Label]label[1,2;Nested containers work too.]image[0,1;1,1;air.png]