2 files changed, 34 insertions, 6 deletions
diff --git a/src/lsp/lsp.zig b/src/lsp/lsp.zig
index 43f94f95..33e95570 100644
--- a/src/lsp/lsp.zig
+++ b/src/lsp/lsp.zig
@@ -31,8 +31,34 @@ pub const Req = struct {
     offset: u32,
     arg: []const u8 = "",
     root: []const u8 = "",
+    /// For `explain`: the query it narrates, read from `arg` (`<kind>
+    /// <arg>`) by `explaining`; a definition when none was asked before.
+    explains: Kind = .definition,
 };
 
+/// An `explain` request made the one it narrates: `explains` and `arg` set
+/// from its `<kind> <arg>`; any other request as it is.
+pub fn explaining(req: Req) Req {
+    if (req.kind != .explain) return req;
+    var r = req;
+    const sp = std.mem.indexOfScalar(u8, req.arg, ' ') orelse req.arg.len;
+    const named = std.meta.stringToEnum(Kind, req.arg[0..sp]) orelse .definition;
+    r.explains = if (named == .explain or named == .status) .definition else named;
+    r.arg = if (sp < req.arg.len) req.arg[sp + 1 ..] else "";
+    return r;
+}
+
+test "an explain request narrates the query named in its arg, a definition by default" {
+    const base: Req = .{ .kind = .explain, .path = "/x.zig", .source = "", .offset = 0 };
+    var r = base;
+    r.arg = "hover ";
+    try std.testing.expectEqual(Kind.hover, explaining(r).explains);
+    r.arg = "rename newName";
+    try std.testing.expectEqual(Kind.rename, explaining(r).explains);
+    try std.testing.expectEqualStrings("newName", explaining(r).arg);
+    try std.testing.expectEqual(Kind.definition, explaining(base).explains);
+}
+
 /// Every language, Zig's (zls) included, through the protocol client, which
 /// runs its server as a child process. None on the web or the board.
 const backends = if (@import("pardes_config").platform == .web or @import("pardes_config").platform == .esp32p4)
diff --git a/src/lsp/lsp_client.zig b/src/lsp/lsp_client.zig
index 7704d0ad..0c5e3b7e 100644
--- a/src/lsp/lsp_client.zig
+++ b/src/lsp/lsp_client.zig
@@ -405,8 +405,9 @@ const Trace = struct {
 
 // ------------------------------------------------------------------- query
 
-pub fn query(gpa: std.mem.Allocator, arena: std.mem.Allocator, req: lsp.Req, out: *std.Io.Writer) !void {
+pub fn query(gpa: std.mem.Allocator, arena: std.mem.Allocator, asked: lsp.Req, out: *std.Io.Writer) !void {
     _ = gpa;
+    const req = lsp.explaining(asked);
     if (req.kind == .status) return status(req, out);
 
     var tr: Trace = .{ .on = req.kind == .explain };
@@ -443,8 +444,8 @@ pub fn query(gpa: std.mem.Allocator, arena: std.mem.Allocator, req: lsp.Req, out
 
 fn traceOut(tr: *const Trace, req: lsp.Req, out: *std.Io.Writer, rows: usize, us: u64) std.Io.Writer.Error!void {
     if (req.kind != .explain) return;
-    try out.print("lsp explain — the definition query at byte {d} of {s}\n\n", .{
-        req.offset, if (req.path.len == 0) "(no file)" else std.fs.path.basename(req.path),
+    try out.print("lsp explain — the {s} query at byte {d} of {s}\n\n", .{
+        @tagName(req.explains), req.offset, if (req.path.len == 0) "(no file)" else std.fs.path.basename(req.path),
     });
     try out.writeAll(tr.buf[0..tr.len]);
     if (hideTime())
@@ -488,9 +489,10 @@ fn answer(arena: std.mem.Allocator, si: usize, req: lsp.Req, out: *std.Io.Writer
 }
 
 fn run(c: *Conn, si: usize, arena: std.mem.Allocator, req: lsp.Req, out: *std.Io.Writer, tr: *Trace) Err!void {
-    // `explain` narrates the definition query — dispatch below on the
-    // effective kind so the trace follows the code `gd` really runs.
-    const kind: lsp.Kind = if (req.kind == .explain) .definition else req.kind;
+    // `explain` narrates the last query asked (a definition, `gd`, when
+    // none was) — dispatch below on the effective kind so the trace
+    // follows the code that query really runs.
+    const kind: lsp.Kind = if (req.kind == .explain) req.explains else req.kind;
 
     // Both arg-taking kinds are useless without one, and an empty
     // workspace/symbol query means "every symbol in the project".