mirror of
https://github.com/danog/psalm.git
synced 2024-12-02 09:37:59 +01:00
83 lines
2.7 KiB
Markdown
83 lines
2.7 KiB
Markdown
# Things that make developing Psalm complicated
|
|
|
|
This is a somewhat informal list that might aid others.
|
|
|
|
## Type inference
|
|
|
|
Type inference is one of the big things Psalm does. It tries to figure out what different PHP elements (function calls, if/for/foreach statements etc.) mean for the data in your code.
|
|
|
|
Within type inference there are a number of tricky areas:
|
|
|
|
#### Loops
|
|
|
|
Loops are hard to reason about - break and continue are a pain. This analysis mainly takes place in `LoopAnalyzer`
|
|
|
|
#### Combining types
|
|
|
|
There are lots of edge-cases when combining types together, given the many types Psalm supports. Type combining occurs in `TypeCombiner`.
|
|
|
|
#### Logical assertions
|
|
|
|
What effect do different PHP elements have on user-asserted logic in if conditionals, ternarys etc. This logic is spread between a number of different classes.
|
|
|
|
#### Generics & Templated code
|
|
|
|
Figuring out how templated code should work (`@template` tags) and how much it should work like it does in other languages (Hack, TypeScript etc.) is tricky. Psalm also supports things like nested templates (`@template T1 of T2`) which makes things trickier
|
|
|
|
## Detecting dead code
|
|
|
|
Detecting unused variables requires some fun [data-flow analysis](https://psalm.dev/articles/better-unused-variable-detection).
|
|
|
|
Detecting unused classes and methods between different runs requires maintaining references to those classes in cache (see below).
|
|
|
|
## Supporting the community
|
|
- **Supporting formal PHPDoc annotations**
|
|
- **Supporting informal PHPDoc annotations**
|
|
e.g. `ArrayIterator|string[]` to denote an `ArrayIterator` over strings
|
|
- **non-Composer projects**
|
|
e.g. WordPress
|
|
|
|
## Making Psalm fast
|
|
|
|
#### Parser-based reflection
|
|
|
|
Requires scanning everything necessary for analysis
|
|
|
|
#### Forking processes** (non-windows)
|
|
|
|
Mostly handled by code borrowed from Phan, but can introduce subtle issues, also requires to think about how to make work happen in processes
|
|
|
|
#### Caching thing
|
|
|
|
see below
|
|
|
|
## Cache invalidation
|
|
|
|
#### Invalidating analysis results
|
|
|
|
Requires tracking what methods/properties are used in what other files, and invalidating those results when linked methods change
|
|
|
|
#### Partial parsing
|
|
|
|
Reparsing bits of files that have changed, which is hard
|
|
|
|
## Language Server Support
|
|
|
|
#### Handling temporary file changes
|
|
|
|
When files change Psalm figures out what's changed within them to avoid re-analysing things unnecessarily
|
|
|
|
#### Dealing with malformed PHP code
|
|
|
|
When people write code, it's not always pretty as they write it. A language server needs to deal with that bad code somehow
|
|
|
|
## Fixing code with Psalter
|
|
|
|
#### Adding/replacing code
|
|
|
|
Figuring out what changed, making edits that could have been made by a human
|
|
|
|
#### Minimal diffs
|
|
|
|
hard to change more than you need
|