EmmyLua Formatter Examples

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This page groups representative before-and-after examples by scenario. The point is not that every construct is formatted the same way, but that the formatter chooses between flat, fill, packed, aligned, and one-per-line layouts based on the rendered result.

1. Basic Flat Formatting

Flat when it fits

Before:

local point={x=1,y=2}

After:

local point = { x = 1, y = 2 }

Small stable structures stay on one line, with spacing and separators normalized.

2. Calls And Parameter Lists

Progressive fill for call arguments

Before:

some_function(first_arg, second_arg, third_arg, fourth_arg)

After:

some_function(
    first_arg, second_arg, third_arg,
    fourth_arg
)

This keeps the argument list compact without immediately forcing one argument per line.

Outer calls may break while inner calls stay compact

Before:

cannotload("attempt to load a text chunk", load(read1(x), "modname", "b", {}))

After:

cannotload(
    "attempt to load a text chunk",
    load(read1(x), "modname", "b", {})
)

The outer call expands because of width pressure, but short nested calls are not blown apart unnecessarily.

Inline comments in parameter lists are preserved

Before:

local f = function(a -- first
, b)
    return a + b
end

After:

local f = function(a -- first
, b)
    return a + b
end

Inline comments in parameter lists are treated conservatively because rewriting them can change how the signature reads.

3. Table Constructors

Small tables stay compact

Before:

local t = { a = 1, b = 2, c = 3 }

After:

local t = { a = 1, b = 2, c = 3 }

Auto mode uses progressive breaking when field alignment is off

Before:

local t = { alpha, beta, gamma, delta }

After:

local t = {
    alpha, beta, gamma,
    delta
}

The formatter tries a compact multi-line distribution before falling back to one item per line.

Nested tables expand by shape, not by blanket rules

Before:

local t = { user = { name = "a", age = 1 }, enabled = true }

After:

local t = { user = { name = "a", age = 1 }, enabled = true }

Having a nested table is not enough on its own to force full expansion.

4. Chains And Expression Sequences

Balanced packed layout for binary chains

Before:

local value = aaaa + bbbb + cccc + dddd + eeee + ffff

After:

local value = aaaa + bbbb
    + cccc + dddd
    + eeee + ffff

Binary-chain candidates are scored with the real first-line prefix width, so long anchors such as local value = affect candidate selection.

Statement expression lists also use balanced packed layouts

Before:

for key, value in first_long_expr, second_long_expr, third_long_expr, fourth_long_expr, fifth_long_expr do
    print(key, value)
end

After:

for key, value in first_long_expr,
    second_long_expr, third_long_expr,
    fourth_long_expr, fifth_long_expr do
    print(key, value)
end

This keeps the first item attached to the keyword line and then packs later items more evenly.

One segment per line when necessary

Before:

builder:set_name(name):set_age(age):build()

After:

builder
    :set_name(name)
    :set_age(age)
    :build()

When fill or packed layouts are clearly worse, the formatter still falls back to one segment per line.

5. Comments And Conservative Preservation

Comment alignment is input-driven

Before:

foo(
    alpha,  -- first
    beta   -- second
)

After:

foo(
    alpha, -- first
    beta   -- second
)

Trailing comments are aligned only when the input already signals alignment intent. The formatter does not manufacture wide alignment blocks across unrelated code.

Inline comments on statement headers stay on the header

Before:

if ready then -- inline comment
    work()
end

After:

if ready then -- inline comment
    work()
end

Moving this kind of comment into the body changes how the control flow reads, so the formatter preserves the header structure.