535 lines
17 KiB
Rust
535 lines
17 KiB
Rust
// signature.rs --- T M4.7 LSP-backed signature help.
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//! Signature-help state and the [`SignatureView`] that renders it.
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//!
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//! Per spec §M4.7: while the cursor is inside a function call, pmacs
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//! sends `textDocument/signatureHelp` to find out what the call's
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//! parameters are. The reply lists candidate signatures (overloads),
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//! with optional pointers to which signature and parameter are
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//! "active" given the current cursor position. The
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//! [`SignatureView`] renders the active signature with the active
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//! parameter highlighted.
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use std::collections::HashMap;
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use std::sync::{Arc, Mutex};
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use serde_json::Value;
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use unicode_width::UnicodeWidthChar;
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use crate::buffer::Buffer;
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use crate::cell::{Cell, CellCoord, CellGrid, Glyph, Style};
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use crate::view::{View, Viewport};
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// ---------------------------------------------------------------------------
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// Types
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// ---------------------------------------------------------------------------
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/// One signature parameter. `range` is a `[start, end]` byte slice
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/// into the parent signature's `label` when the LSP gives offsets;
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/// `text` is the full parameter label when the LSP gives a string.
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/// Parsing collapses both onto a `(label, span)` pair where `span`
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/// is `Some` iff offsets were provided.
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#[derive(Clone, Debug)]
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pub struct SignatureParameter {
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/// Parameter label, either the standalone string form or the
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/// substring of the parent signature that the offsets point at.
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pub label: String,
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/// Optional `[start, end]` byte offsets into the signature's
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/// `label`. Only populated when the LSP supplied them; the LSP
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/// `[number, number]` form is converted to `Some((start, end))`.
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pub span: Option<(u32, u32)>,
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/// Optional documentation.
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pub documentation: Option<String>,
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}
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/// One full signature (one overload). LSP allows multiple signatures
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/// to share an `activeParameter`; pmacs preserves the per-signature
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/// override if present.
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#[derive(Clone, Debug)]
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pub struct Signature {
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/// Full signature label (e.g. `fn echo(name: &str, count: usize)`).
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pub label: String,
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/// Optional documentation.
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pub documentation: Option<String>,
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/// Parameters in declaration order.
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pub parameters: Vec<SignatureParameter>,
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/// Per-signature `activeParameter` override; `None` falls back to
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/// the response-level `active_parameter`.
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pub active_parameter: Option<u32>,
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}
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/// Parsed `textDocument/signatureHelp` response.
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#[derive(Clone, Debug, Default)]
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pub struct SignatureHelp {
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/// Candidate signatures (overloads).
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pub signatures: Vec<Signature>,
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/// Index of the active signature; `0` if missing.
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pub active_signature: u32,
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/// Default active parameter, used when a signature doesn't carry
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/// its own `active_parameter`.
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pub active_parameter: Option<u32>,
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}
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impl SignatureHelp {
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/// Parse the LSP `SignatureHelp` JSON object. Returns an empty
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/// help (no signatures) for `null`.
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#[must_use]
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pub fn from_lsp_value(v: &Value) -> Self {
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if v.is_null() {
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return Self::default();
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}
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let signatures = v
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.get("signatures")
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.and_then(Value::as_array)
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.map(|arr| arr.iter().filter_map(parse_signature).collect::<Vec<_>>())
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.unwrap_or_default();
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let active_signature = v
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.get("activeSignature")
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.and_then(Value::as_u64)
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.map_or(0, |n| n as u32);
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let active_parameter = v
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.get("activeParameter")
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.and_then(Value::as_u64)
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.map(|n| n as u32);
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Self {
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signatures,
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active_signature,
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active_parameter,
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}
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}
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/// Currently active signature, or `None` if `signatures` is empty
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/// or the index is out of range.
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#[must_use]
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pub fn active(&self) -> Option<&Signature> {
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self.signatures.get(self.active_signature as usize)
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}
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/// Active parameter index for the active signature, falling back
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/// to the response-level default.
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#[must_use]
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pub fn active_parameter_index(&self) -> Option<u32> {
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self.active()
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.and_then(|s| s.active_parameter)
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.or(self.active_parameter)
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}
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}
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fn parse_signature(v: &Value) -> Option<Signature> {
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let label = v.get("label")?.as_str()?.to_owned();
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let documentation = v.get("documentation").and_then(extract_markup_text);
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let parameters = v
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.get("parameters")
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.and_then(Value::as_array)
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.map(|arr| {
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arr.iter()
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.filter_map(|p| parse_parameter(p, &label))
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.collect::<Vec<_>>()
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})
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.unwrap_or_default();
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let active_parameter = v
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.get("activeParameter")
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.and_then(Value::as_u64)
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.map(|n| n as u32);
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Some(Signature {
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label,
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documentation,
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parameters,
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active_parameter,
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})
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}
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fn parse_parameter(v: &Value, parent_label: &str) -> Option<SignatureParameter> {
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let label_field = v.get("label")?;
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let documentation = v.get("documentation").and_then(extract_markup_text);
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if let Some(s) = label_field.as_str() {
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return Some(SignatureParameter {
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label: s.to_owned(),
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span: None,
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documentation,
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});
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}
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if let Some(arr) = label_field.as_array()
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&& arr.len() == 2
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{
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let start = arr[0].as_u64()? as u32;
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let end = arr[1].as_u64()? as u32;
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let s = parent_label
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.get(start as usize..end as usize)
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.unwrap_or("")
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.to_owned();
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return Some(SignatureParameter {
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label: s,
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span: Some((start, end)),
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documentation,
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});
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}
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None
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}
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fn extract_markup_text(v: &Value) -> Option<String> {
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if let Some(s) = v.as_str() {
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return Some(s.to_owned());
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}
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if let Some(obj) = v.as_object()
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&& let Some(s) = obj.get("value").and_then(Value::as_str)
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{
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return Some(s.to_owned());
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}
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None
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}
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/// Per-server, per-uri signature-help state.
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#[derive(Default)]
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pub struct SignatureStore {
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by_key: HashMap<SignatureKey, SignatureHelp>,
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}
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/// Key into [`SignatureStore`].
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#[derive(Clone, Eq, PartialEq, Hash, Debug)]
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pub struct SignatureKey {
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/// LSP server id (decimal).
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pub server: String,
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/// Document URI.
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pub uri: String,
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}
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impl SignatureKey {
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/// Construct a key.
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#[must_use]
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pub fn new(server: impl Into<String>, uri: impl Into<String>) -> Self {
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Self {
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server: server.into(),
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uri: uri.into(),
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}
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}
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}
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impl SignatureStore {
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/// Empty store.
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#[must_use]
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pub fn new() -> Self {
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Self::default()
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}
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/// Replace the help at `key`. Empty `signatures` drops the entry.
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pub fn set(&mut self, key: SignatureKey, help: SignatureHelp) {
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if help.signatures.is_empty() {
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self.by_key.remove(&key);
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} else {
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self.by_key.insert(key, help);
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}
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}
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/// Drop the help at `key`.
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pub fn clear(&mut self, key: &SignatureKey) {
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self.by_key.remove(key);
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}
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/// Look up the help at `key`.
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#[must_use]
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pub fn get(&self, key: &SignatureKey) -> Option<&SignatureHelp> {
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self.by_key.get(key)
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}
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/// All keys currently in the store.
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pub fn keys(&self) -> impl Iterator<Item = &SignatureKey> {
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self.by_key.keys()
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}
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}
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/// Cheaply-cloneable shared handle.
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pub type SharedSignatureStore = Arc<Mutex<SignatureStore>>;
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/// Build a fresh shared store.
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#[must_use]
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pub fn make_shared_store() -> SharedSignatureStore {
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Arc::new(Mutex::new(SignatureStore::new()))
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}
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// ---------------------------------------------------------------------------
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// View
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// ---------------------------------------------------------------------------
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/// Style for the active parameter --- bold + underline so the
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/// emphasis carries on monochrome and palette terminals alike.
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fn active_parameter_style() -> Style {
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Style {
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bold: true,
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underline: crate::cell::UnderlineStyle::Single,
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..Style::default()
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}
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}
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/// Popup view that renders the active signature, highlighting the
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/// active parameter.
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pub struct SignatureView {
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key: SignatureKey,
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store: SharedSignatureStore,
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}
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impl SignatureView {
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/// Construct a signature view for `key` against `store`.
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#[must_use]
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pub fn new(key: SignatureKey, store: SharedSignatureStore) -> Self {
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Self { key, store }
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}
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/// The key this view is keyed under.
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#[must_use]
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pub fn key(&self) -> &SignatureKey {
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&self.key
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}
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}
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/// Snapshot of just the bits the renderer needs --- avoids holding
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/// the lock across the render loop.
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struct SignatureSnapshot {
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label: String,
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/// Optional `(start, end)` byte span of the active parameter
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/// inside `label`.
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active_span: Option<(u32, u32)>,
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/// Active parameter label (used when there's no span).
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active_label: Option<String>,
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/// Optional documentation line for the active signature.
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documentation: Option<String>,
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}
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impl SignatureView {
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fn snapshot(&self) -> Option<SignatureSnapshot> {
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let guard = self.store.lock().expect("signature store poisoned");
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let help = guard.get(&self.key)?;
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let sig = help.active()?;
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let active_idx = help.active_parameter_index();
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let (active_span, active_label) = match active_idx {
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Some(i) => match sig.parameters.get(i as usize) {
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Some(p) => (p.span, Some(p.label.clone())),
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None => (None, None),
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},
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None => (None, None),
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};
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Some(SignatureSnapshot {
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label: sig.label.clone(),
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active_span,
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active_label,
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documentation: sig.documentation.clone(),
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})
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}
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}
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impl View for SignatureView {
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fn render(&mut self, _buf: &Buffer, viewport: Viewport, cells: &mut CellGrid<'_>) {
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let snap = self.snapshot();
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let max_rows = viewport.cell_size.rows;
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let max_cols = viewport.cell_size.cols;
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let origin = viewport.cell_origin;
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for r in 0..max_rows {
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for c in 0..max_cols {
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*cells.at(CellCoord::new(origin.row + r, origin.col + c)) = Cell::default();
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}
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}
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let Some(snap) = snap else {
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return;
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};
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// Resolve the active span. Prefer offsets when present;
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// otherwise locate the active parameter's substring in the
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// label.
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let active_byte_range: Option<(usize, usize)> = match (snap.active_span, &snap.active_label)
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{
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(Some((s, e)), _) => Some((s as usize, e as usize)),
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(None, Some(lbl)) => snap.label.find(lbl.as_str()).map(|i| (i, i + lbl.len())),
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(None, None) => None,
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};
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// Row 0: signature label, with the active parameter range
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// styled. Row 1+: optional documentation, one line each
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// (truncated at viewport).
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if max_rows > 0 {
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let label_bytes = snap.label.as_bytes();
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let mut col: u32 = 0;
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let mut byte_idx: usize = 0;
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for ch in snap.label.chars() {
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if col >= max_cols {
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break;
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}
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let width = char_display_width(ch);
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if width == 0 {
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byte_idx += ch.len_utf8();
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continue;
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}
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let in_active =
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active_byte_range.is_some_and(|(s, e)| byte_idx >= s && byte_idx < e);
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let style = if in_active {
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active_parameter_style()
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} else {
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Style::default()
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};
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let cell = cells.at(CellCoord::new(origin.row, origin.col + col));
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cell.glyph = Glyph::Char(ch);
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cell.style = style;
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cell.attachment = None;
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col += 1;
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if width == 2 && col < max_cols {
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let cont = cells.at(CellCoord::new(origin.row, origin.col + col));
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cont.glyph = Glyph::Continuation;
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cont.style = style;
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cont.attachment = None;
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col += 1;
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}
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byte_idx += ch.len_utf8();
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let _ = label_bytes; // silence unused-field on minor refactors
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}
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}
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if max_rows > 1
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&& let Some(doc) = snap.documentation.as_deref()
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{
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for (i, line) in doc.lines().enumerate() {
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let row_idx = i as u32 + 1;
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if row_idx >= max_rows {
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break;
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}
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let mut col: u32 = 0;
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for ch in line.chars() {
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if col >= max_cols {
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break;
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}
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let width = char_display_width(ch);
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if width == 0 {
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continue;
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}
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let cell = cells.at(CellCoord::new(origin.row + row_idx, origin.col + col));
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cell.glyph = Glyph::Char(ch);
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cell.style = Style::default();
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cell.attachment = None;
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col += 1;
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if width == 2 && col < max_cols {
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let cont = cells.at(CellCoord::new(origin.row + row_idx, origin.col + col));
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cont.glyph = Glyph::Continuation;
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cont.style = Style::default();
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cont.attachment = None;
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col += 1;
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}
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}
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}
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}
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}
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}
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fn char_display_width(ch: char) -> u32 {
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UnicodeWidthChar::width(ch).unwrap_or(0) as u32
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}
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// ---------------------------------------------------------------------------
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// Tests
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// ---------------------------------------------------------------------------
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#[cfg(test)]
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mod tests {
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use super::*;
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use serde_json::json;
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#[test]
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fn from_lsp_value_parses_signature_help() {
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let v = json!({
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"signatures": [
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{
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"label": "fn echo(name: &str, count: usize) -> String",
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"documentation": "Echoes name count times.",
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"parameters": [
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{ "label": "name: &str" },
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{ "label": "count: usize" }
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],
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"activeParameter": 1
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}
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],
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"activeSignature": 0,
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"activeParameter": 1
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});
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let h = SignatureHelp::from_lsp_value(&v);
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assert_eq!(h.signatures.len(), 1);
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assert_eq!(h.active_signature, 0);
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assert_eq!(h.active_parameter, Some(1));
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let sig = h.active().unwrap();
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assert_eq!(sig.parameters.len(), 2);
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assert_eq!(sig.parameters[1].label, "count: usize");
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assert_eq!(h.active_parameter_index(), Some(1));
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}
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#[test]
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fn parameter_label_with_offsets_extracts_substring() {
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let label = "fn f(a: i32, b: i32)";
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let v = json!({
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"signatures": [
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{
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"label": label,
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"parameters": [
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{ "label": [5, 11] }, // "a: i32"
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{ "label": [13, 19] } // "b: i32"
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]
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}
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],
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"activeSignature": 0,
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"activeParameter": 0
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});
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let h = SignatureHelp::from_lsp_value(&v);
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let sig = h.active().unwrap();
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assert_eq!(sig.parameters[0].label, "a: i32");
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assert_eq!(sig.parameters[0].span, Some((5, 11)));
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assert_eq!(sig.parameters[1].label, "b: i32");
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}
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#[test]
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fn from_lsp_value_handles_null() {
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let h = SignatureHelp::from_lsp_value(&Value::Null);
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assert!(h.signatures.is_empty());
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assert!(h.active().is_none());
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assert!(h.active_parameter_index().is_none());
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}
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#[test]
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fn signature_active_parameter_overrides_top_level() {
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let v = json!({
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"signatures": [
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{
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"label": "fn x(a, b)",
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"parameters": [{"label": "a"}, {"label": "b"}],
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"activeParameter": 0
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}
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],
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"activeSignature": 0,
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"activeParameter": 1
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});
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let h = SignatureHelp::from_lsp_value(&v);
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// Per-signature override wins.
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assert_eq!(h.active_parameter_index(), Some(0));
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}
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#[test]
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fn store_set_get_clear() {
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let mut s = SignatureStore::new();
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let key = SignatureKey::new("1", "file:///a");
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let h = SignatureHelp::from_lsp_value(&json!({
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"signatures": [{ "label": "fn x()", "parameters": [] }],
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"activeSignature": 0
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}));
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s.set(key.clone(), h);
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assert!(s.get(&key).is_some());
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s.clear(&key);
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assert!(s.get(&key).is_none());
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}
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#[test]
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fn empty_signatures_drops_entry() {
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let mut s = SignatureStore::new();
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let key = SignatureKey::new("1", "file:///a");
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s.set(
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key.clone(),
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SignatureHelp::from_lsp_value(&json!({"signatures": [], "activeSignature": 0})),
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);
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assert!(s.get(&key).is_none());
|
|
}
|
|
}
|