Mob.Formatter (mob v0.5.16)

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mix format plugin for the ~MOB sigil.

Add Mob.Formatter to your project's .formatter.exs and mix format will automatically normalise every ~MOB sigil in your codebase alongside all other Elixir code:

# .formatter.exs
[
  plugins: [Mob.Formatter],
  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
]

What it normalises

  • Consistent indentation — children are indented 2 spaces per nesting level.
  • Attribute wrapping — when a tag's inline attributes would exceed line_length, each attribute moves to its own line with the closing /> or > on a separate line.
  • Expression children — {expr} slots are indented to match their sibling nodes.
  • Idempotent — running mix format twice produces the same result.

See the Tooling & Formatting guide for before/after examples and CI setup instructions.

Configuration

Respects the standard line_length option from .formatter.exs:

[
  plugins: [Mob.Formatter],
  line_length: 120,
  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
]

The default line length is 98 characters.

Pass-through behaviour

If the ~MOB template cannot be parsed (e.g. the file is in a mid-edit incomplete state), the formatter returns the content unchanged rather than raising. mix format never breaks a file it cannot fully understand.

Mismatched open/close tag names (e.g. <Column>...</Row>) are silently corrected to use the open tag name. The ~MOB sigil itself raises a CompileError at compile time for mismatched tags, so the formatted file will still surface the error on the next mix compile.