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✨ Update LSP types to more recent version (#324)
See #324 --------- Signed-off-by: JonahSussman <[email protected]> Signed-off-by: Jonah Sussman <[email protected]>
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| # Protocol generator tool | ||
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| Originally from: https://github.com/golang/tools/tree/master/gopls/internal/lsp/protocol | ||
| Commit id: If4c85191760baef916911130ca315773d2adda1f | ||
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| ## How to use | ||
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| If there is an update to the LSP specification, navigate to the `protocol` directory and run `go generate`. This will generate all the types needed for the analyzer. You need to add `ExtendedClientCapilities map[string]interface{} `json:"extendedClientCapabilities"`` to XInitializeParams struct. Other than that, you should be good to go. | ||
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| ## Changes | ||
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| - Commented out `writeclient()` and `writeserver()` in generate/main.go | ||
| - Commented out `"Or_WorkspaceFoldersServerCapabilities_changeNotifications": "string",` in generate/tables.go | ||
| - Changed `type DocumentURI string` to `type DocumentURI = string` in generate/output.go | ||
| - Need to add `ExtendedClientCapilities map[string]interface{} `json:"extendedClientCapabilities"`` to XInitializeParams struct. Need to figure out why needed. Can remove if not. |
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| // Copyright 2020 The Go Authors. All rights reserved. | ||
| // Use of this source code is governed by a BSD-style | ||
| // license that can be found in the LICENSE file. | ||
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| package protocol | ||
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| // Custom code actions that aren't explicitly stated in LSP | ||
| const ( | ||
| GoTest CodeActionKind = "goTest" | ||
| // TODO: Add GoGenerate, RegenerateCgo etc. | ||
| ) |
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| Original file line number | Diff line number | Diff line change |
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| # LSP Support for gopls | ||
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| ## The protocol | ||
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| The LSP protocol exchanges json-encoded messages between the client and the server. | ||
| (gopls is the server.) The messages are either Requests, which require Responses, or | ||
| Notifications, which generate no response. Each Request or Notification has a method name | ||
| such as "textDocument/hover" that indicates its meaning and determines which function in the server will handle it. | ||
| The protocol is described in a | ||
| [web page](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.18/specification/), | ||
| in words, and in a json file (metaModel.json) available either linked towards the bottom of the | ||
| web page, or in the vscode-languageserver-node repository. This code uses the latter so the | ||
| exact version can be tied to a githash. By default, the command will download the `github.com/microsoft/vscode-languageserver-node` repository to a temporary directory. | ||
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| The specification has five sections | ||
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| 1. Requests, which describe the Request and Response types for request methods (e.g., *textDocument/didChange*), | ||
| 2. Notifications, which describe the Request types for notification methods, | ||
| 3. Structures, which describe named struct-like types, | ||
| 4. TypeAliases, which describe type aliases, | ||
| 5. Enumerations, which describe named constants. | ||
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| Requests and Notifications are tagged with a Method (e.g., `"textDocument/hover"`). | ||
| The specification does not specify the names of the functions that handle the messages. These | ||
| names are specified by the `methodNames` map. Enumerations generate Go `const`s, but | ||
| in Typescript they are scoped to namespaces, while in Go they are scoped to a package, so the Go names | ||
| may need to be modified to avoid name collisions. (See the `disambiguate` map, and its use.) | ||
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| Finally, the specified types are Typescript types, which are quite different from Go types. | ||
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| ### Optionality | ||
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| The specification can mark fields in structs as Optional. The client distinguishes between missing | ||
| fields and `null` fields in some cases. The Go translation for an optional type | ||
| should be making sure the field's value | ||
| can be `nil`, and adding the json tag `,omitempty`. The former condition would be satisfied by | ||
| adding `*` to the field's type if the type is not a reference type. | ||
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| ### Types | ||
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| The specification uses a number of different types, only a few of which correspond directly to Go types. | ||
| The specification's types are "base", "reference", "map", "literal", "stringLiteral", "tuple", "and", "or". | ||
| The "base" types correspond directly to Go types, although some Go types needs to be chosen for `URI` and `DocumentUri`. (The "base" types`RegExp`, `BooleanLiteral`, `NumericLiteral` never occur.) | ||
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| "reference" types are the struct-like types in the Structures section of the specification. The given | ||
| names are suitable for Go to use, except the code needs to change names like `_Initialze` to `XInitialize` so | ||
| they are exported for json marshaling and unmarshaling. | ||
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| "map" types are just like Go. (The key type in all of them is `DocumentUri`.) | ||
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| "stringLiteral" types are types whose type name and value are a single string. The chosen Go equivalent | ||
| is to make the type `string` and the value a constant. (The alternative would be to generate a new | ||
| named type, which seemed redundant.) | ||
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| "literal" types are like Go anonymous structs, so they have to be given a name. (All instances | ||
| of the remaining types have to be given names. One approach is to construct the name from the components | ||
| of the type, but this leads to misleading punning, and is unstable if components are added. The other approach | ||
| is to construct the name from the context of the definition, that is, from the types it is defined within. | ||
| For instance `Lit__InitializeParams_clientInfo` is the "literal" type at the | ||
| `clientInfo` field in the `_InitializeParams` | ||
| struct. Although this choice is sensitive to the ordering of the components, the code uses this approach, | ||
| presuming that reordering components is an unlikely protocol change.) | ||
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| "tuple" types are generated as Go structs. (There is only one, with two `uint32` fields.) | ||
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| "and" types are Go structs with embedded type names. (There is only one, `And_Param_workspace_configuration`.) | ||
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| "or" types are the most complicated. There are a lot of them and there is no simple Go equivalent. | ||
| They are defined as structs with a single `Value interface{}` field and custom json marshaling | ||
| and unmarshaling code. Users can assign anything to `Value` but the type will be checked, and | ||
| correctly marshaled, by the custom marshaling code. The unmarshaling code checks types, so `Value` | ||
| will have one of the permitted types. (`nil` is always allowed.) There are about 40 "or" types that | ||
| have a single non-null component, and these are converted to the component type. | ||
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| ## Processing | ||
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| The code parses the json specification file, and scans all the types. It assigns names, as described | ||
| above, to the types that are unnamed in the specification, and constructs Go equivalents as required. | ||
| (Most of this code is in typenames.go.) | ||
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| There are four output files. tsclient.go and tsserver.go contain the definition and implementation | ||
| of the `protocol.Client` and `protocol.Server` types and the code that dispatches on the Method | ||
| of the Request or Notification. tsjson.go contains the custom marshaling and unmarshaling code. | ||
| And tsprotocol.go contains the type and const definitions. | ||
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| ### Accommodating gopls | ||
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| As the code generates output, mostly in generateoutput.go and main.go, | ||
| it makes adjustments so that no changes are required to the existing Go code. | ||
| (Organizing the computation this way makes the code's structure simpler, but results in | ||
| a lot of unused types.) | ||
| There are three major classes of these adjustments, and leftover special cases. | ||
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| The first major | ||
| adjustment is to change generated type names to the ones gopls expects. Some of these don't change the | ||
| semantics of the type, just the name. | ||
| But for historical reasons a lot of them replace "or" types by a single | ||
| component of the type. (Until fairly recently Go only saw or used only one of components.) | ||
| The `goplsType` map in tables.go controls this process. | ||
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| The second major adjustment is to the types of fields of structs, which is done using the | ||
| `renameProp` map in tables.go. | ||
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| The third major adjustment handles optionality, controlling `*` and `,omitempty` placement when | ||
| the default rules don't match what gopls is expecting. (The map is `goplsStar`, also in tables.go) | ||
| (If the intermediate components in expressions of the form `A.B.C.S` were optional, the code would need | ||
| a lot of useless checking for nils. Typescript has a language construct to avoid most checks.) | ||
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| Then there are some additional special cases. There are a few places with adjustments to avoid | ||
| recursive types. For instance `LSPArray` is `[]LSPAny`, but `LSPAny` is an "or" type including `LSPArray`. | ||
| The solution is to make `LSPAny` an `interface{}`. Another instance is `_InitializeParams.trace` | ||
| whose type is an "or" of 3 stringLiterals, which just becomes a `string`. | ||
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| ### Checking | ||
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| `TestAll(t *testing.T)` checks that there are no unexpected fields in the json specification. | ||
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| While the code is executing, it checks that all the entries in the maps in tables.go are used. | ||
| It also checks that the entries in `renameProp` and `goplsStar` are not redundant. | ||
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| As a one-time check on the first release of this code, diff-ing the existing and generated tsclient.go | ||
| and tsserver.go code results in only whitespace and comment diffs. The existing and generated | ||
| tsprotocol.go differ in whitespace and comments, and in a substantial number of new type definitions | ||
| that the older, more heuristic, code did not generate. (And the unused type `_InitializeParams` differs | ||
| slightly between the new and the old, and is not worth fixing.) | ||
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| ### Some history | ||
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| The original stub code was written by hand, but with the protocol under active development, that | ||
| couldn't last. The web page existed before the json specification, but it lagged the implementation | ||
| and was hard to process by machine. So the earlier version of the generating code was written in Typescript, and | ||
| used the Typescript compiler's API to parse the protocol code in the repository. | ||
| It then used a set of heuristics | ||
| to pick out the elements of the protocol, and another set of overlapping heuristics to create the Go code. | ||
| The output was functional, but idiosyncratic, and the code was fragile and barely maintainable. | ||
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| ### The future | ||
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| Most of the adjustments using the maps in tables.go could be removed by making changes, mostly to names, | ||
| in the gopls code. Using more "or" types in gopls requires more elaborate, but stereotyped, changes. | ||
| But even without all the adjustments, making this its own module would face problems; a number of | ||
| dependencies would have to be factored out. And, it is fragile. The custom unmarshaling code knows what | ||
| types it expects. A design that return an 'any' on unexpected types would match the json | ||
| 'ignore unexpected values' philosophy better, but the Go code would need extra checking. |
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