apache / apache/datafusion-sqlparser-rs

[EPIC] Complete Span (source location) information / feature

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Rust
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Description

This ticket tracks the work remaining to complete adding source location information into sqlparser

## Background
- @Nyrox and @iffyio introduced the foundations for storing source location information in the AST nodes in https://github.com/apache/datafusion-sqlparser-rs/pull/1435. This information can be used to provide more specific error messages, and potentially syntax highlighting among other great things.
- In order to 1. minimize the disruption to downstream projects that use `sqlparser-rs` and 2. avoid a single massive PR and 3. work together as a community, we are implementing this feature incrementally over several releases.

Let's use this ticket to organize needed / remaining work. If you find additional features are needed / issues, please leave a comment on this ticket

## Source Span Contributing Guidelines

For contributing source spans improvement in addition to the general
[contribution guidelines], please make sure to pay attention to the
following:

- `Ident` always have correct source spans

- We try to minimize downstream breaking changes

- Consider using [`Span::union`] in favor of storing spans on all nodes
- Any metadata added to compute spans must not change semantics (`Eq`, `Ord`, `Hash`, etc.). See [`AttachedToken`] for more information.

[contribution guidelines]: https://github.com/apache/datafusion-sqlparser-rs/blob/main/README.md#contributing
[`Span::union`]: ast::Span::union
[`AttachedToken`]: ast::helpers::attached_token::AttachedToken

When adding support for source spans on a type, consider the impact to consumers of that type and whether your change would require a consumer to do non-trivial changes to their code.

Example of a trivial change

```rust
match node {
ast::Query {
field1,
field2,
location: _, // add a new line to ignored location
}

If adding source spans to a type would require a significant change like wrapping the type, please open an issue to discuss.

# AST Node Equality and Hashes

When adding tokens to AST nodes, make sure to store them using the [AttachedToken](https://docs.rs/sqlparser/latest/sqlparser/ast/helpers/struct.AttachedToken.html) (TODO UPDATE SOURCE REFERENCE)to ensure that semantically equivalent AST nodes compare as equal and hash to the same value. i.e. `select 5` and `SELECT 5` would compare as different `Select` nodes, if the select token was stored directly. f.e.

```rust
struct Select {
select_token: AttachedToken, // only used for spans
/// remaining fields
field1,
field2,
...
}
```

Some high level work (list from https://github.com/apache/datafusion-sqlparser-rs/pull/1435)
- Store keyword `TokenWithLocation` for expressions that currently don't have them
- Implement spans for the rest of the AST, namely `Statement`s

## Tasks

- [ ] https://github.com/apache/datafusion-sqlparser-rs/issues/1563
- [ ] Look into reducing AST size with smaller offset sizes (e.g. `u32` rather than `usize`)
- [ ] Store spans for ast::value::Value
- [x] https://github.com/apache/datafusion-sqlparser-rs/issues/1858
- [ ] https://github.com/apache/datafusion-sqlparser-rs/issues/1548

Contributor guide

No contributing guide indexed for this repository

Research direction

Start by reading PR 1435 and the source-span contributing guidelines, especially ast::Span::union and ast::helpers::attached_token::AttachedToken. Review the unchecked tasks and the AST areas they name, including Statements and ast::value::Value. Done would require completing a clearly scoped remaining task while preserving AST semantics and minimizing downstream changes.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust, sql
Domain
compilers, databases
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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