145 lines
5.4 KiB
Markdown
145 lines
5.4 KiB
Markdown
# php2go
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Convert PHP source code to Go by AST walking.
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The goal is to produce idiomatic, maintainable Go code as part of a one-off conversion. This is not generally possible for highly dynamic PHP code, that may require manual fixups.
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## Progress
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### Phase 1
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[X] Convert some small programs
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[X] Error handling
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- [X] All functions return `(type, error)`
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- [X] Convert `throw` to err return
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- [X] Non-leaf function calls need to check + bubble errors
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[X] Array handling
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- [X] Infer whether to use slice/map for PHP array
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[-] Namespaces
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- [X] Basic support for `namespace` -> package name transformation
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- [ ] Resolve namespace names in calls
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- [ ] Resolve `use` statements
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[X] `if`
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[X] `for`/`foreach`
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[X] `switch`
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[ ] Generators
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[ ] Goto
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[X] `null` -> `nil`
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[X] Consts and `define()`
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- [X] Magic constants (`__LINE__`,`__FILE__` etc)
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[ ] `isset`/`unset`
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[ ] `instanceof`
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[X] `die`
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[X] `try`/`catch`/`finally`
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- [X] Implement using err checks, not panic/recover
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- Any statements within the try block should capture the finally/catch to run within any interior err-check blocks
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- [ ] `finally`
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- Runs before any return statement inside the try block or catch block; also runs after the try block is complete
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- Maybe `finally` would be more concisely implemented as defer inside an IIFE, but that is not idiomatic, maintainable Go code
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[X] Abandon upon sight of highly dynamic constructs
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- [X] `eval`
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- [X] `extract`
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- [ ] variable-variables
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- [ ] Attempts to enable magic_quotes or register_globals
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[X] Detect assignment expressions
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- Go doesn't support assignment in rvalues, only as a statement
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- When walking below stmt level, need to first fully walk and check for any function calls + assignments that may need hoisting (and we can probably only do that correctly if there is no short-circuiting)
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- [X] Add subtree walk + catch error for this case
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[X] Closures
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- [ ] Handle value/reference captures
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[X] Convert top-level calls to `init()`/`main()`
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- [X] Wrap in function
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- [X] Determine init/main based on package name
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[ ] Class/object transformations
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- [X] Convert `new X` constructor calls to `NewX`
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- [X] Visibility
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- [X] Apply PHP visibility modifiers as Go case change
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- [ ] Call mangled function name at call sites
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- *PHP variable names are case-sensitive, function names are case-insensitive*
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- [X] Static methods
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- [X] Inheritance *partial*
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- [X] Interfaces
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- [X] Class constants
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- [X] super
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- [X] Need to track current conversion state through into function generator, to select the concrete parent
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- [X] parent::
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- [X] self::
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- [ ] static::
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- [ ] Traits / `use`
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- [ ] Abstract methods
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[X] Track golang package imports
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[X] Variadic function parameters
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[X] Preserve comments
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### Productionize
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[ ] Multi-file programs
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- [ ] Include/Require
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[ ] Infer whether to declare variable (`var` / `:=`) or reuse (`=`)
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- [ ] Track current visibility scope
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[ ] Comprehensive coverage of all AST node types
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- [X] Create full-coverage interface to implement
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- [ ] Node
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- [ ] Stmt
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- [ ] Expr
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- [ ] Assign
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- [X] Binary
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- [X] Scalar
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- [X] Heredocs/nowdocs
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[ ] Numbered break/continue
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[ ] Type inference
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- [ ] Type declarations for literals (string, slice/map with constant initializer, etc)
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- [ ] Convert known PHP typenames to Go equivalents
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- [ ] Parse extra types from phpdoc blocks
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[ ] Hoisting pass for rvalue expressions
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- [ ] Behaviour of function calls in rvalue cases where err cannot be checked
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- [ ] Assignment expressions
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- [ ] Alternately - we can support the form `if foo := bar(); foo {`
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- [ ] Ternarys
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[ ] Simple standard library transformations
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- [X] common string/array functions
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- [ ] More string/array functions
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- [ ] Top 100 from https://www.exakat.io/top-100-php-functions/
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- [ ] substr -> slice index operator
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- This has the same value semantics for string literals, but not variables
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- [ ] error_reporting(E_ALL) --> just remove it
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- [ ] ini_set('display_errors', 'On') --> remove it when the parameter is known
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[ ] Elide error return for functions that cannot throw
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- ?? Could be a standalone Go refactoring tool
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### Wishlist
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[ ] Extended library/environment transformations
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- [ ] Standard library transformations
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- [X] Track golang package imports
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- [ ] Handle conflicts between golang stdlib packages / local variable names
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- [ ] uasort -> sort.Slice
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- [ ] preg -> regexp
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- [ ] json -> encoding/json
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- [ ] Output buffering (`ob_start` / `ob_get_clean`)
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- Can push/pop os.Stdout onto a private stack, then we can keep using `fmt.Print`
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- [ ] PHP Superglobal transformations
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- [ ] `$_SERVER['argv']` to os.Args
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- [ ] `$_GET['name']` to r.FormValue('name')
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- [ ] Common 3rd party package transformations to popular equivalents (optional)
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- [ ] Guzzle
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- [ ] AWS SDK
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- [ ] PHPUnit -> Go Test
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- [ ] Replace Composer/PSR-4 autoloading with Go imports
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[ ] Preserve rough line spacing
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[ ] Somehow detect whether map use should be order-preserving
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[ ] Support scoped namespace (`namespace { ... }`) and multiple namespaces in file
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[ ] Validation on imported comment formats
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[ ] Convert wordpress / mediawiki / symfony
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- [ ] Option to convert with preset=cli, preset=web, webroot path
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- [ ] Option to generate built-in web server
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[ ] Generate source maps
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- The parser does have full positional information - exporting at the stmt level would be reasonable
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- But the gofmt pass may lose this information
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[ ] Command-line tool option to `go run`
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## Reference
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- [The Go Programming Language Specification](https://golang.org/ref/spec)
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