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Updated protocol to more recent version
Signed-off-by: JonahSussman <[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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# 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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