Migrating to v1.0¶

The most notable change of the v1.0 release of pygls is the removal of its hand written LSP type and method definitions in favour of relying on the types provided by the lsprotocol library which are automatically generated from the LSP specification. As as side effect this has also meant the removal of pydantic as a dependency, since lsprotocol uses attrs and cattrs for serialisation and validation.

This guide outlines how to adapt an existing server to the breaking changes introduced in this release.

Known Migrations¶

You may find insight and inspiration from these projects that have already successfully migrated to v1:

Updating Imports¶

The pygls.lsp.methods and pygls.lsp.types modules no longer exist. Instead, all types and method names should now be imported from the lsprotocol.types module.

Additionally, the following types and constants have been renamed.

pygls	lsprotocol
`CODE_ACTION`	`TEXT_DOCUMENT_CODE_ACTION`
`CODE_LENS`	`TEXT_DOCUMENT_CODE_LENS`
`COLOR_PRESENTATION`	`TEXT_DOCUMENT_COLOR_PRESENTATION`
`COMPLETION`	`TEXT_DOCUMENT_COMPLETION`
`DECLARATION`	`TEXT_DOCUMENT_DECLARATION`
`DEFINITION`	`TEXT_DOCUMENT_DEFINITION`
`DOCUMENT_COLOR`	`TEXT_DOCUMENT_DOCUMENT_COLOR`
`DOCUMENT_HIGHLIGHT`	`TEXT_DOCUMENT_DOCUMENT_HIGHLIGHT`
`DOCUMENT_LINK`	`TEXT_DOCUMENT_DOCUMENT_LINK`
`DOCUMENT_SYMBOL`	`TEXT_DOCUMENT_DOCUMENT_SYMBOL`
`FOLDING_RANGE`	`TEXT_DOCUMENT_FOLDING_RANGE`
`FORMATTING`	`TEXT_DOCUMENT_FORMATTING`
`HOVER`	`TEXT_DOCUMENT_HOVER`
`IMPLEMENTATION`	`TEXT_DOCUMENT_IMPLEMENTATION`
`LOG_TRACE_NOTIFICATION`	`LOG_TRACE`
`ON_TYPE_FORMATTING`	`TEXT_DOCUMENT_ON_TYPE_FORMATTING`
`PREPARE_RENAME`	`TEXT_DOCUMENT_PREPARE_RENAME`
`PROGRESS_NOTIFICATION`	`PROGRESS`
`RANGE_FORMATTING`	`TEXT_DOCUMENT_RANGE_FORMATTING`
`REFERENCES`	`TEXT_DOCUMENT_REFERENCES`
`RENAME`	`TEXT_DOCUMENT_RENAME`
`SELECTION_RANGE`	`TEXT_DOCUMENT_SELECTION_RANGE`
`SET_TRACE_NOTIFICATION`	`SET_TRACE`
`SIGNATURE_HELP`	`TEXT_DOCUMENT_SIGNATURE_HELP`
`TEXT_DOCUMENT_CALL_HIERARCHY_INCOMING_CALLS`	`CALL_HIERARCHY_INCOMING_CALLS`
`TEXT_DOCUMENT_CALL_HIERARCHY_OUTGOING_CALLS`	`CALL_HIERARCHY_OUTGOING_CALLS`
`TEXT_DOCUMENT_CALL_HIERARCHY_PREPARE`	`TEXT_DOCUMENT_PREPARE_CALL_HIERARCHY`
`TYPE_DEFINITION`	`TEXT_DOCUMENT_TYPE_DEFINITION`
`WORKSPACE_FOLDERS`	`WORKSPACE_WORKSPACE_FOLDERS`
`ApplyWorkspaceEditResponse`	`ApplyWorkspaceEditResult`
`ClientInfo`	`InitializeParamsClientInfoType`
`CodeActionDisabled`	`CodeActionDisabledType`
`CodeActionLiteralSupportActionKindClientCapabilities`	`CodeActionClientCapabilitiesCodeActionLiteralSupportTypeCodeActionKindType`
`CodeActionLiteralSupportClientCapabilities`	`CodeActionClientCapabilitiesCodeActionLiteralSupportType`
`CompletionItemClientCapabilities`	`CompletionClientCapabilitiesCompletionItemType`
`CompletionItemKindClientCapabilities`	`CompletionClientCapabilitiesCompletionItemKindType`
`CompletionTagSupportClientCapabilities`	`CompletionClientCapabilitiesCompletionItemTypeTagSupportType`
`DocumentSymbolCapabilitiesTagSupport`	`DocumentSymbolClientCapabilitiesTagSupportType`
`InsertTextModeSupportClientCapabilities`	`CompletionClientCapabilitiesCompletionItemTypeInsertTextModeSupportType`
`MarkedStringType`	`MarkedString`
`MarkedString`	`MarkedString_Type1`
`PrepareRename`	`PrepareRenameResult_Type1`
`PublishDiagnosticsTagSupportClientCapabilities`	`PublishDiagnosticsClientCapabilitiesTagSupportType`
`ResolveSupportClientCapabilities`	`CodeActionClientCapabilitiesResolveSupportType`
`SemanticTokensRequestsFull`	`SemanticTokensRegistrationOptionsFullType1`
`SemanticTokensRequests`	`SemanticTokensClientCapabilitiesRequestsType`
`ServerInfo`	`InitializeResultServerInfoType`
`ShowMessageRequestActionItem`	`ShowMessageRequestClientCapabilitiesMessageActionItemType`
`SignatureHelpInformationClientCapabilities`	`SignatureHelpClientCapabilitiesSignatureInformationType`
`SignatureHelpInformationParameterInformationClientCapabilities`	`SignatureHelpClientCapabilitiesSignatureInformationTypeParameterInformationType`
`TextDocumentContentChangeEvent`	`TextDocumentContentChangeEvent_Type1`
`TextDocumentContentChangeTextEvent`	`TextDocumentContentChangeEvent_Type2`
`TextDocumentSyncOptionsServerCapabilities`	`TextDocumentSyncOptions`
`Trace`	`TraceValues`
`URI`	`str`
`WorkspaceCapabilitiesSymbolKind`	`WorkspaceSymbolClientCapabilitiesSymbolKindType`
`WorkspaceCapabilitiesTagSupport`	`WorkspaceSymbolClientCapabilitiesTagSupportType`
`WorkspaceFileOperationsServerCapabilities`	`FileOperationOptions`
`WorkspaceServerCapabilities`	`ServerCapabilitiesWorkspaceType`

Custom Models¶

One of the most obvious changes is the switch to attrs and cattrs for serialization and deserialisation. This means that any custom models used by your language server will need to be converted to an attrs style class.

# Before
from pydantic import BaseModel, Field

class ExampleConfig(BaseModel):
    build_dir: Optional[str] = Field(None, alias="buildDir")

    builder_name: str = Field("html", alias="builderName")

    conf_dir: Optional[str] = Field(None, alias="confDir")

# After
import attrs

@attrs.define
class ExampleConfig:
    build_dir: Optional[str] = attrs.field(default=None)

    builder_name: str = attrs.field(default="html")

    conf_dir: Optional[str] = attrs.field(default=None)

Pygls provides a default converter that it will use when converting your models to/from JSON, which should be sufficient for most scenarios.

>>> from pygls.protocol import default_converter
>>> converter = default_converter()

>>> config = ExampleConfig(builder_name='epub', conf_dir='/path/to/conf')
>>> converter.unstructure(config)
{'builderName': 'epub', 'confDir': '/path/to/conf'}   # Note how snake_case is converted to camelCase

>>> converter.structure({'builderName': 'epub', 'confDir': '/path/to/conf'}, ExampleConfig)
ExampleConfig(build_dir=None, builder_name='epub', conf_dir='/path/to/conf')

However, depending on the complexity of your type definitions you may find the default converter fail to parse some of your types.

>>> from typing import Literal, Union

>>> @attrs.define
... class ExampleConfig:
...     num_jobs: Union[Literal["auto"], int] = attrs.field(default='auto')
...

>>> converter.structure({'numJobs': 'auto'}, ExampleConfig)
  + Exception Group Traceback (most recent call last):
  |   File "<stdin>", line 1, in <module>
  |   File "/.../python3.10/site-packages/cattrs/converters.py", li
ne 309, in structure
  |     return self._structure_func.dispatch(cl)(obj, cl)
  |   File "<cattrs generated structure __main__.ExampleConfig-2>", line 10, in structure_ExampleConfig
  |     if errors: raise __c_cve('While structuring ' + 'ExampleConfig', errors, __cl)
  | cattrs.errors.ClassValidationError: While structuring ExampleConfig (1 sub-exception)
  +-+---------------- 1 ----------------
    | Traceback (most recent call last):
    |   File "<cattrs generated structure __main__.ExampleConfig-2>", line 6, in structure_ExampleConfig
    |     res['num_jobs'] = __c_structure_num_jobs(o['numJobs'], __c_type_num_jobs)
    |   File "/.../python3.10/site-packages/cattrs/converters.py",
line 377, in _structure_error
    |     raise StructureHandlerNotFoundError(msg, type_=cl)
    | cattrs.errors.StructureHandlerNotFoundError: Unsupported type: typing.Union[typing.Literal['auto'], int].
 Register a structure hook for it.
    | Structuring class ExampleConfig @ attribute num_jobs
    +------------------------------------

In which case you can extend the converter provided by pygls with your own structure hooks

from pygls.protocol import default_converter

def custom_converter():
    converter = default_converter()
    converter.register_structure_hook(Union[Literal['auto', int], lambda obj, _: obj)

    return converter

You can then override the default converter used by pygls when constructing your language server instance

server = LanguageServer(
    name="my-language-server", version="v1.0", converter_factory=custom_converter
)

See the hooks.py module in lsprotocol for some example structure hooks

Miscellaneous¶

Mandatory `name` and `version`¶

It is now necessary to provide a name and version when constructing an instance of the LanguageServer class

from pygls.server import LanguageServer

server = LanguageServer(name="my-language-server", version="v1.0")

`ClientCapabilities.get_capability` is now `get_capability`¶

# Before
from pygls.lsp.types import ClientCapabilities

client_capabilities = ClientCapabilities()
commit_character_support = client_capabilities.get_capability(
   "text_document.completion.completion_item.commit_characters_support", False
)

# After
from lsprotocol.types import ClientCapabilities
from pygls.capabilities import get_capability

client_capabilities = ClientCapabilities()
commit_character_support = get_capability(
   client_capabilities,
   "text_document.completion.completion_item.commit_characters_support",
   False
)