Add-ED

The standard editor, now as a library

Some time ago I decided to write an ED clone with syntax highlighting, hired. On my way to that I found that the macro commands (g, v, G, V, :) pretty much require that you write an ED library for them. So I did, and here it is.

Differences from GNU Ed

I have taken some liberties in the commands I have found less than ergonomic, so especially advanced commands have some differences (both syntax and behaviour) from GNU Ed. This strives to be a list of these changes.

• g and related commands take command list in input mode (with the regex separator as terminator instead of '.'). (Also, the 'I' suffix for case insensitive matching isn't implemented)
• # accepts a selection and will set state.selection to it without printing anything. This is added to be able to set selection without printing.

Core concepts

The selection:

The original ED keeps track of the last line you interacted with and defaults to working on that for most commands. I felt this deserved expanding, so add-ed instead tracks the last span of lines you interacted with. My hope is that this is more intuitive. (To avoid unpleasantries such as partial saving some commands default to the whole buffer instead, ie. w .)

Flexible APIs

The library has been designed with clear traits to enable changing out most components easily. For example it should be somewhat easy to create a SSH/SFTP IO implementation for remote editing, a GUI frontend implementing the UI trait or a MacroGetter that loads macros from any given filepath.

New features compared to Ed

• A and I commands, which first a/i and then j the preceding/following line. Perfect for commenting out a single line or adding a forgotten ';'.

• C command, acts as c but hands out the selection's previous value to the UI's input method. This enables you to edit the selection instead of replacing it.

  (Availability depends on UI and the initial_input_data feature.)

• P command, toggles the default for the given print flags.

• : command, runs the macro with the name given as argument (whitespace trimmed). Macro execution behaves like 'g' execution. 'q' or error returns early.

• | command, pipes selection through given shell command (like <selection>! does in vim). It is distinct from ! to enable defaulting to current selection when no explicit selection is given.

Feature flags:

local_io:

Include and expose a simple local fs and shell IO implementation.

initial_input_data:

Add 'C' command. This modifies the UI trait.

serde:

#[derive(serde::Serialize, serde::Deserialize)] on Macro struct.

Other structs can get derived on upon request, but Macro (and its members) was the only one that seemed relevant.

Attributions:

This project is essentially built upon the regex crate, as regex is the heart of Ed.

Contributing:

There are two main contributions welcomed as of now.

1. Adding tests. Though core uses for command are tested, more behaviours should be validated. If you have the time, add test cases that validate that:
   • Commands behave as COMMANDS.md states.
   • Commands behave same as in GNU Ed, unless otherwise documented in the Differences from GNU Ed section above.
2. Checking off ToDo:s. Look into the TODOS.md file, pick a task to do and go wild. You can add a PR to prevent others from working on the same task (mark it as WIP until relevant to review).
3. Create issues for undocumented or unexpected behaviour.
4. Request support for your use-cases. Create a feature request issue for what you need. (Look into POTENTIAL_FEATURES.md to see if a similar feature is prepared and if so note it in the feature request.)