Say which basedpython constructs a document uses, from the tree rather than from the text

`by/explainTranspilation` reports every basedpython-specific construct in a
document and what each lowers to. A client that wanted this had to guess from the
source text — one regex for `?.`, another for `??`, another for `data class` —
and a regex cannot tell an operator from the same characters inside a string or a
comment, cannot see that `?` in a type position means something else, and drifts
from the language the moment a construct is added.

The parser here is the one the transpiler runs, so the answer is the one the
lowering is about to act on. `?.` in particular is not looked for at all: the
parser records it as a flag on the access, so this reports what was written
rather than what the characters resemble.

`by/transpile` also takes a fragment now. A selection has no document of its own,
and the alternative — writing it to a temp file and running the CLI over that —
is the thing the request exists to remove; the document it names is only what
routes the request to a server.

Author: KotlinIsland

Cargo.lock

@@ -9,9 +9,9 @@ pub use locator::Locator;
 pub use noqa::{SuppressionKind, generate_suppression_edits};
 #[cfg(feature = "clap")]
 pub use registry::clap_completion::RuleParser;
+pub use rule_documentation::rule_documentation;
 #[cfg(feature = "clap")]
 pub use rule_selector::clap_completion::UnresolvedRuleSelectorParser;
-pub use rule_documentation::rule_documentation;
 pub use rule_selector::{RuleSelector, UnresolvedRuleSelector};
 pub use rules::pycodestyle::rules::IOError;
 
@@ -41,8 +41,8 @@ pub mod packaging;
 pub mod preview;
 pub mod registry;
 mod renamer;
-mod rule_redirects;
 pub mod rule_documentation;
+mod rule_redirects;
 pub mod rule_selector;
 pub mod rules;
 pub mod settings;

crates/basedpython/Cargo.lock

@@ -20,6 +20,7 @@ ruff_diagnostics = { workspace = true }
 ruff_macros = { workspace = true }
 ruff_notebook = { workspace = true }
 ruff_python_ast = { workspace = true }
+ruff_python_parser = { workspace = true }
 ruff_source_file = { workspace = true }
 ruff_ranged_value = { workspace = true }
 ruff_text_size = { workspace = true }

crates/ruff_linter/src/lib.rs

@@ -94,6 +94,9 @@ pub(super) fn request(req: server::Request) -> Task {
         requests::TranspileRequestHandler::METHOD => background_document_request_task::<
             requests::TranspileRequestHandler,
         >(req, BackgroundSchedule::Worker),
+        requests::ExplainTranspilationHandler::METHOD => background_document_request_task::<
+            requests::ExplainTranspilationHandler,
+        >(req, BackgroundSchedule::Worker),
         requests::SemanticTokensRequestHandler::METHOD => background_document_request_task::<
             requests::SemanticTokensRequestHandler,
         >(req, BackgroundSchedule::Worker),

crates/ty_server/Cargo.toml

@@ -18,12 +18,12 @@ mod code_action;
 mod code_lens;
 mod completion;
 mod data_flow;
-mod explain_rule;
-mod transpile;
 mod diagnostic;
 mod doc_highlights;
 mod document_symbols;
 mod execute_command;
+mod explain_rule;
+mod explain_transpilation;
 mod folding_range;
 mod goto_declaration;
 mod goto_definition;
@@ -41,6 +41,7 @@ mod semantic_tokens;
 mod semantic_tokens_range;
 mod shutdown;
 mod signature_help;
+mod transpile;
 mod type_hierarchy_subtypes;
 mod type_hierarchy_supertypes;
 mod workspace_diagnostic;
@@ -52,12 +53,12 @@ pub(super) use code_action::CodeActionRequestHandler;
 pub(super) use code_lens::CodeLensRequestHandler;
 pub(super) use completion::CompletionRequestHandler;
 pub(super) use data_flow::DataFlowRequestHandler;
-pub(super) use explain_rule::ExplainRuleHandler;
-pub(super) use transpile::TranspileRequestHandler;
 pub(super) use diagnostic::DocumentDiagnosticRequestHandler;
 pub(super) use doc_highlights::DocumentHighlightRequestHandler;
 pub(super) use document_symbols::DocumentSymbolRequestHandler;
 pub(super) use execute_command::ExecuteCommand;
+pub(super) use explain_rule::ExplainRuleHandler;
+pub(super) use explain_transpilation::ExplainTranspilationHandler;
 pub(super) use folding_range::FoldingRangeRequestHandler;
 pub(super) use goto_declaration::GotoDeclarationRequestHandler;
 pub(super) use goto_definition::GotoDefinitionRequestHandler;
@@ -75,6 +76,7 @@ pub(super) use semantic_tokens::SemanticTokensRequestHandler;
 pub(super) use semantic_tokens_range::SemanticTokensRangeRequestHandler;
 pub(super) use shutdown::ShutdownHandler;
 pub(super) use signature_help::SignatureHelpRequestHandler;
+pub(super) use transpile::TranspileRequestHandler;
 pub(super) use type_hierarchy_subtypes::TypeHierarchySubtypesRequestHandler;
 pub(super) use type_hierarchy_supertypes::TypeHierarchySupertypesRequestHandler;
 pub(super) use workspace_diagnostic::WorkspaceDiagnosticRequestHandler;

crates/ty_server/src/server/api.rs

@@ -15,8 +15,8 @@ use ty_python_semantic::default_lint_registry;
 use crate::server::api::traits::{
     BackgroundRequestHandler, RequestHandler, RetriableRequestHandler,
 };
-use crate::session::client::Client;
 use crate::session::SessionSnapshot;
+use crate::session::client::Client;
 
 pub(crate) enum ExplainRuleRequest {}