From 7ffb5fc4fdafd37c1bc03ab24c2b7083d4424162 Mon Sep 17 00:00:00 2001
From: Lily Brown <lbrown@roblox.com>
Date: Mon, 7 Feb 2022 12:08:43 -0800
Subject: [PATCH] Add Luau.Ast.CLI target (#345)

Adds a `luau-ast` CLI that dumps Luau source to JSON. @asajeffrey and I are planning to use this functionality to construct an Agda model of the Luau type system/operational semantics, to allow formally proving properties of Luau's type systems.
---
 CLI/Ast.cpp    | 84 ++++++++++++++++++++++++++++++++++++++++++++++++++
 CMakeLists.txt |  5 +++
 Sources.cmake  |  7 +++++
 3 files changed, 96 insertions(+)
 create mode 100644 CLI/Ast.cpp

diff --git a/CLI/Ast.cpp b/CLI/Ast.cpp
new file mode 100644
index 00000000..4ea46236
--- /dev/null
+++ b/CLI/Ast.cpp
@@ -0,0 +1,84 @@
+// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
+#include <optional>
+
+#include "Luau/Common.h"
+#include "Luau/Ast.h"
+#include "Luau/JsonEncoder.h"
+#include "Luau/Parser.h"
+#include "Luau/ParseOptions.h"
+
+#include "FileUtils.h"
+
+static void displayHelp(const char* argv0)
+{
+    printf("Usage: %s [file]\n", argv0);
+}
+
+static int assertionHandler(const char* expr, const char* file, int line, const char* function)
+{
+    printf("%s(%d): ASSERTION FAILED: %s\n", file, line, expr);
+    return 1;
+}
+
+int main(int argc, char** argv)
+{
+    Luau::assertHandler() = assertionHandler;
+
+    for (Luau::FValue<bool>* flag = Luau::FValue<bool>::list; flag; flag = flag->next)
+        if (strncmp(flag->name, "Luau", 4) == 0)
+            flag->value = true;
+
+    if (argc >= 2 && strcmp(argv[1], "--help") == 0)
+    {
+        displayHelp(argv[0]);
+        return 0;
+    }
+    else if (argc < 2)
+    {
+        displayHelp(argv[0]);
+        return 1;
+    }
+
+    const char* name = argv[1];
+    std::optional<std::string> maybeSource = std::nullopt;
+    if (strcmp(name, "-") == 0)
+    {
+        maybeSource = readStdin();
+    }
+    else
+    {
+        maybeSource = readFile(name);
+    }
+
+    if (!maybeSource)
+    {
+        fprintf(stderr, "Couldn't read source %s\n", name);
+        return 1;
+    }
+
+    std::string source = *maybeSource;
+
+    Luau::Allocator allocator;
+    Luau::AstNameTable names(allocator);
+
+    Luau::ParseOptions options;
+    options.supportContinueStatement = true;
+    options.allowTypeAnnotations = true;
+    options.allowDeclarationSyntax = true;
+
+    Luau::ParseResult parseResult = Luau::Parser::parse(source.data(), source.size(), names, allocator, options);
+
+    if (parseResult.errors.size() > 0)
+    {
+        fprintf(stderr, "Parse errors were encountered:\n");
+        for (const Luau::ParseError& error : parseResult.errors)
+        {
+            fprintf(stderr, "  %s - %s\n", toString(error.getLocation()).c_str(), error.getMessage().c_str());
+        }
+        fprintf(stderr, "\n");
+    }
+
+    printf("%s", Luau::toJson(parseResult.root).c_str());
+
+    return parseResult.errors.size() > 0 ? 1 : 0;
+}
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 881d3c3f..efef6e3a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -21,10 +21,12 @@ add_library(isocline STATIC)
 if(LUAU_BUILD_CLI)
     add_executable(Luau.Repl.CLI)
     add_executable(Luau.Analyze.CLI)
+    add_executable(Luau.Ast.CLI)
 
     # This also adds target `name` on Linux/macOS and `name.exe` on Windows
     set_target_properties(Luau.Repl.CLI PROPERTIES OUTPUT_NAME luau)
     set_target_properties(Luau.Analyze.CLI PROPERTIES OUTPUT_NAME luau-analyze)
+    set_target_properties(Luau.Ast.CLI PROPERTIES OUTPUT_NAME luau-ast)
 endif()
 
 if(LUAU_BUILD_TESTS)
@@ -98,6 +100,7 @@ endif()
 if(LUAU_BUILD_CLI)
     target_compile_options(Luau.Repl.CLI PRIVATE ${LUAU_OPTIONS})
     target_compile_options(Luau.Analyze.CLI PRIVATE ${LUAU_OPTIONS})
+    target_compile_options(Luau.Ast.CLI PRIVATE ${LUAU_OPTIONS})
 
     target_include_directories(Luau.Repl.CLI PRIVATE extern extern/isocline/include)
 
@@ -111,6 +114,8 @@ if(LUAU_BUILD_CLI)
     endif()
 
     target_link_libraries(Luau.Analyze.CLI PRIVATE Luau.Analysis)
+
+    target_link_libraries(Luau.Ast.CLI PRIVATE Luau.Ast Luau.Analysis)
 endif()
 
 if(LUAU_BUILD_TESTS)
diff --git a/Sources.cmake b/Sources.cmake
index b36b6db5..4ab1d98e 100644
--- a/Sources.cmake
+++ b/Sources.cmake
@@ -193,6 +193,13 @@ if(TARGET Luau.Analyze.CLI)
         CLI/Analyze.cpp)
 endif()
 
+if (TARGET Luau.Ast.CLI)
+    target_sources(Luau.Ast.CLI PRIVATE
+        CLI/FileUtils.h
+        CLI/FileUtils.cpp
+        CLI/Ast.cpp)
+endif()
+
 if(TARGET Luau.UnitTest)
     # Luau.UnitTest Sources
     target_sources(Luau.UnitTest PRIVATE