# Does anyone want to take over maintenance of the Kowainik ecosystem?

> Source: <https://discourse.haskell.org/t/does-anyone-want-to-take-over-maintenance-of-the-kowainik-ecosystem/15010#post_9>
> Published: 2026-11-09 22:54:07+00:00

Hi! I really like tomland, especially for its bidirectional codecs, and it made […](https://github.com/kowainik/tomland/pull/470)me a bit sad to see it fall behind the spec.
Now that I have Claude at my side, I thought I'd put in the effort to push through some changes that were planned years ago (#248, #264, #373). There are a few of them and they are necessarily API-breaking, so I made sure to split them into individual commits that add up to full TOML 1.1.0 support.
The short version: against the official [toml-test](https://github.com/toml-lang/toml-test) suite (the `files-toml-1.1.0` list), the parser now accepts all 218 valid documents and rejects all 494 invalid ones.
Closes #373, closes #248, closes #264.
### What's in here
The commits fall roughly into three groups.
**Parser** (`dc09f7d`..` dac66c7`). Mostly about the TOML 1.0 rules that weren't enforced, plus the 1.1 additions:
- whitespace, newlines and comments are only consumed where the spec allows them. `sc` now consumes only spaces and tabs and a new `scn` handles newlines/comments. A key/value pair or header has to be followed by a newline;
- whitespace around dots in keys, ASCII-only bare keys;
- string rules: `\e` and `\xHH` (1.1), tabs and non-ASCII in basic strings, control characters rejected in literal strings, `""` before the closing `"""`, etc.;
- times without seconds (1.1), lowercase `t`/` z`, range-checked offsets, no leading zeros in floats or `0_1`;
- inline tables can span lines and have a trailing comma (1.1), and can be nested in inline tables and arrays.
There are two printer fixes in this group too, because the round-trip tests started failing on them. `MultiLine` mode printed `key =` followed by a newline, which isn't valid TOML. Control characters were printed with `show`, so you'd get `\ESC`, which no TOML parser accepts.
**Mixed arrays and unquoted keys** (`c4d29d5`, `20fd317`).
- `Array` holds `[AnyValue]` instead of `[Value t]`. There's a new `array` helper for the homogeneous case and an `_Either` BiMap to decode into a sum type.
- `Piece` used to keep the quotes, so `key`, `"key"` and `'key'` were three different keys. The spec says they're the same key, and a codec had to know how the file spelled it. Now the parser strips the quotes and the printer adds them back when a piece isn't a bare key.
**New AST and validator** (`a9b79c2`). This one is the big one and it's basically #264. The old `TOML` had two ways to encode a nested table, either as a prefix-tree sibling or as a nested sub-document, and which one you got depended on the order of headers in the file. As a result:
- lookups and `Eq` depended on header order;
- reopening a parent after a subtable duplicated the subtree;
- `int "a.b"` and `table (int "b") "a"` read different places;
- the validator had no idea which tables could still be extended, so it accepted 43 invalid documents from toml-test.
Now `TOML` is a map from a single `Piece` to an `Entry`:
``` haskell
data Entry
    = EValue AnyValue
    | ETable TableKind TOML
    | ETableArray (NonEmpty TOML)
data TableKind = HeaderTable | ImplicitTable | DottedTable | InlineTable
```
Every level of nesting is exactly one piece, so `a.b.c = 1`, `[a.b]` + `c = 1` and `a = { b = { c = 1 } }` all produce the same document. `TableKind` exists only so the validator can apply the 1.1 rules (inline tables are closed, dotted tables can't be reopened with a header, and so on). `Eq` ignores it. `Value` and `TOML` are now mutually recursive (`Table :: TOML -> Value 'TTable` for inline tables inside arrays), so they both live in `Toml.Type.Value`.
The validator is now a single sequential pass that tracks scopes, with a new `ExtendClosedTable` error.
### Compatibility
This is a breaking change, so I've bumped the version to 1.4.0.0. I tried to keep the damage limited to people who work with the AST directly:
- the codec API is unchanged, and existing codecs should keep working. `list`/` nonEmpty` read both `[[key]]` and `key = [ {..}, {..} ]`;
- `tomlPairs`, `tomlTables` and `tomlTableArrays` are still there as deprecated read-only functions with their old types, and `Toml.Type.PrefixTree` is kept as a deprecated module. My suggestion would be to drop them in 1.5;
- two things can't be shimmed: `Array` holding `AnyValue`, and `Piece` being unquoted. The second one is the nasty one, because `Piece "\"a.b\""` still compiles but now means something different. I wrote a "Migrating from 1.3" section in the changelog that covers both.
### Testing
- `cabal test`: 328 examples, 0 failures (GHC 9.12.4 locally; I haven't tried the rest of the CI matrix yet, so let's see what CI says).
- toml-test, 1.1.0 list: 218/218 valid accepted, 494/494 invalid rejected. tomland doesn't ship a toml-test decoder, so this is an accept/reject sweep with a small `runghc` script that calls `Toml.Parser.parse`. It doesn't check the decoded values against the expected JSON. Happy to add the script (or a proper decoder executable) to the repo if you think it's worth it.
- For what it's worth, the 1.0.0 list gives 208/208 and 492/501. The 9 misses are exactly the things 1.1 relaxed: times without seconds, multi-line inline tables and trailing commas in them, and `\x` escapes. There's no "1.0 mode", and I don't think one is needed.
### Open questions
- Even split into commits, it's still a lot to review. The parser commits come before the AST change and stand on their own (the test suite passes at `dac66c7`), so I can split them into a separate PR if that's easier for you.
- I haven't measured performance. The new representation should be in the same ballpark (`HashMap` per level instead of a prefix tree), but I haven't checked.