Add an action for adding a docstring snippet with the method signatur…

…e to a method definition.

src/requests/actions.jl

@@ -576,6 +576,45 @@ function convert_from_raw(x, _, conn)
     return nothing
 end
 
+# Checks if parent is a parent/grandparent/... of child
+function is_parent_of(parent::EXPR, child::EXPR)
+    while child isa EXPR
+        if child == parent
+            return true
+        end
+        child = child.parent
+    end
+    return false
+end
+
+function is_in_function_signature(x::EXPR, params; with_docstring=false)
+    # TODO: Perhaps also allow this if the cursor is inside a docstring?
+    func = _get_parent_fexpr(x, CSTParser.defines_function)
+    func === nothing && return false
+    sig = func.args[1]
+    if x.head === :FUNCTION || is_parent_of(sig, x)
+        hasdoc = func.parent isa EXPR && func.parent.head === :macrocall && func.parent.args[1] isa EXPR &&
+                 func.parent.args[1].head === :globalrefdoc
+        return with_docstring == hasdoc
+    end
+    return false
+end
+
+function add_docstring_template(x, _, conn)
+    is_in_function_signature(x, nothing) || return
+    func = _get_parent_fexpr(x, CSTParser.defines_function)
+    func === nothing && return
+    file, func_offset = get_file_loc(func)
+    sig = func.args[1]
+    _, sig_offset = get_file_loc(sig)
+    docstr = "\"\"\"\n    " * get_text(file)[sig_offset .+ (1:sig.span)] * "\n\nTBW\n\"\"\"\n"
+    tde = TextDocumentEdit(VersionedTextDocumentIdentifier(get_uri(file), get_version(file)), TextEdit[
+        TextEdit(Range(file, func_offset:func_offset), docstr)
+    ])
+    JSONRPC.send(conn, workspace_applyEdit_request_type, ApplyWorkspaceEditParams(missing, WorkspaceEdit(missing, TextDocumentEdit[tde])))
+    return
+end
+
 # Adding a CodeAction requires defining:
 # * a unique id
 # * a description
@@ -682,3 +721,12 @@ LSActions["RewriteAsRegularString"] = ServerAction(
     (x, _) -> is_string_literal(x; inraw=true),
     convert_from_raw,
 )
+
+LSActions["AddDocstringTemplate"] = ServerAction(
+    "AddDocstringTemplate",
+    "Add docstring template for this method",
+    missing,
+    missing,
+    is_in_function_signature,
+    add_docstring_template,
+)

test/requests/actions.jl

@@ -148,5 +148,48 @@ end
     raw_str = "he\$l\"lo"
     str = "\"he\\\$l\\\"lo\"" # Will be `"he\$l\"lo` when unescaped/printed
     @test repr(raw_str) == str
+end
+
+@testset "Add docstring template" begin
+    doc = settestdoc("""
+        f(x) = x
+
+        @inline f(x) = x
 
+        f(x::T) where T <: Int = x
+
+        function g(x)
+        end
+
+        function g(x::T) where T <: Int
+        end
+
+        "docstring"
+        h(x) = x
+
+        "docstring"
+        function h(x)
+        end
+        """)
+
+    ok_locations = [
+        [(0, i) for i in 0:3],
+        [(2, i) for i in 8:11],
+        [(4, i) for i in 0:21],
+        [(6, i) for i in 0:12],
+        [(9, i) for i in 0:30],
+    ]
+    not_ok_locations = [
+        [(13, i) for i in 0:4],
+        [(16, i) for i in 0:12],
+    ]
+    for loc in Iterators.flatten(ok_locations)
+        @test any(c.command == "AddDocstringTemplate" for c in action_request_test(loc...))
+    end
+    for loc in Iterators.flatten(not_ok_locations)
+        @test !any(c.command == "AddDocstringTemplate" for c in action_request_test(loc...))
+    end
+
+    c = filter(c -> c.command == "AddDocstringTemplate", action_request_test(0, 1))[1]
+    LanguageServer.workspace_executeCommand_request(LanguageServer.ExecuteCommandParams(missing, c.command, c.arguments), server, server.jr_endpoint)
 end