Add option to trigger the code completion from cli

Author: robertoraggi

src/frontend/cxx/frontend.cc

@@ -218,6 +218,18 @@ auto runOnFile(const CLI& cli, const std::string& fileName) -> bool {
     preprocessor->undefMacro(macro);
   }
 
+  if (auto completion = cli.getSingle("-code-completion-at")) {
+    auto re = std::regex(R"((.*):(\d+):(\d+))");
+    std::smatch match;
+    if (std::regex_match(*completion, match, re)) {
+      auto line = std::stoi(match[2]);
+      auto column = std::stoi(match[3]);
+      preprocessor->requestCodeCompletionAt(line, column);
+    } else {
+      std::cerr << "cxx: invalid argument to -code-completion-at\n";
+    }
+  }
+
   auto outputs = cli.get("-o");
 
   auto outfile = !outputs.empty() && outputs.back() != "-"

src/parser/cxx/cli.cc

@@ -199,6 +199,8 @@ std::vector<CLIOptionDescr> options{
 
     {"-j", "<n>", "Run <n> jobs in parallel.", CLIOptionDescrKind::kSeparated},
 
+    {"-code-completion-at", "<file>:<line>:<column>", CLIOptionDescrKind::kJoined},
+
     {"-v", "Show commands to run and use verbose output", &CLI::opt_v},
 
 };

src/parser/cxx/parser.cc

@@ -38,7 +38,12 @@
 #include <algorithm>
 #include <cstring>
 #include <format>
+#include <iostream>
 #include <ranges>
+#include <unordered_set>
+
+#include "cxx/source_location.h"
+#include "cxx/token_fwd.h"
 
 namespace cxx {
 
@@ -1503,6 +1508,14 @@ auto Parser::parse_unqualified_id(UnqualifiedIdAST*& yyast,
                                   NestedNameSpecifierAST* nestedNameSpecifier,
                                   bool isTemplateIntroduced,
                                   bool inRequiresClause) -> bool {
+  if (!stopParsing_ && lookat(TokenKind::T_CODE_COMPLETION)) {
+    stopParsing_ = true;
+
+    warning(std::format("requested code completion of unqualified-id"));
+
+    consumeToken();
+  }
+
   auto lookat_template_id = [&] {
     LookaheadParser lookahead{this};
 
@@ -2434,6 +2447,14 @@ auto Parser::parse_member_expression(ExpressionAST*& yyast) -> bool {
 
   ast->isTemplateIntroduced = match(TokenKind::T_TEMPLATE, ast->templateLoc);
 
+  if (!stopParsing_ && lookat(TokenKind::T_CODE_COMPLETION)) {
+    stopParsing_ = true;
+
+    warning(std::format("requested code completion of member access"));
+
+    consumeToken();
+  }
+
   if (!parse_unqualified_id(ast->unqualifiedId, ast->nestedNameSpecifier,
                             ast->isTemplateIntroduced,
                             /*inRequiresClause*/ false))
@@ -5184,6 +5205,16 @@ auto Parser::parse_attribute_declaration(DeclarationAST*& yyast) -> bool {
 
 auto Parser::parse_decl_specifier(SpecifierAST*& yyast, DeclSpecs& specs)
     -> bool {
+  if (!stopParsing_ && lookat(TokenKind::T_CODE_COMPLETION)) {
+    stopParsing_ = true;
+
+    warning(
+        std::format("requested code completion of decl specifier in scope '{}'",
+                    to_string(scope_->owner()->name())));
+
+    consumeToken();
+  }
+
   switch (TokenKind(LA())) {
     case TokenKind::T_TYPEDEF: {
       auto ast = make_node<TypedefSpecifierAST>(pool_);
@@ -5666,6 +5697,13 @@ auto Parser::parse_named_type_specifier(SpecifierAST*& yyast, DeclSpecs& specs)
   SourceLocation templateLoc;
   const auto isTemplateIntroduced = match(TokenKind::T_TEMPLATE, templateLoc);
 
+  if (SourceLocation completionLoc;
+      match(TokenKind::T_CODE_COMPLETION, completionLoc)) {
+    stopParsing_ = true;
+    parse_warn(completionLoc, "code completion at type specifier");
+    return false;
+  }
+
   if (!lookat(TokenKind::T_IDENTIFIER)) return false;
 
   UnqualifiedIdAST* unqualifiedId = nullptr;

src/parser/cxx/parser.h

@@ -108,6 +108,7 @@ class Parser final {
   static auto prec(TokenKind tk) -> Prec;
 
   [[nodiscard]] auto shouldStopParsing() const -> bool {
+    if (stopParsing_) return true;
     if (config_.stopParsingPredicate) return config_.stopParsingPredicate();
     return false;
   }
@@ -871,7 +872,7 @@ class Parser final {
   std::uint32_t cursor_ = 0;
   int templateParameterDepth_ = -1;
   int templateParameterCount_ = 0;
-
+  bool stopParsing_ = false;
   std::vector<FunctionDefinitionAST*> pendingFunctionDefinitions_;
 
   template <typename T>