LibCore: Migrate Command from Deprecated{File,String}

This gives us free error-propagation in Core::command(...) and
HackStudio::ProjectBuilder::for_each_library_dependencies.

The comment about "String will be in the null state" has been misleading
for a long time, so it is removed.

Userland/DevTools/HackStudio/Git/GitRepo.cpp

@@ -80,10 +80,10 @@ DeprecatedString GitRepo::command(Vector<DeprecatedString> const& command_parts)
 
 DeprecatedString GitRepo::command_wrapper(Vector<DeprecatedString> const& command_parts, DeprecatedString const& chdir)
 {
-    auto result = Core::command("git", command_parts, LexicalPath(chdir));
+    auto const result = Core::command("git", command_parts, LexicalPath(chdir));
     if (result.is_error() || result.value().exit_code != 0)
         return {};
-    return result.value().output;
+    return DeprecatedString(result.value().output.bytes());
 }
 
 bool GitRepo::git_is_installed()

Userland/DevTools/HackStudio/ProjectBuilder.cpp

@@ -209,7 +209,7 @@ void ProjectBuilder::for_each_library_definition(Function<void(DeprecatedString,
     }
 
     static Regex<ECMA262> const parse_library_definition(R"~~~(.+:serenity_lib[c]?\((\w+) (\w+)\).*)~~~");
-    for (auto& line : res.value().output.split('\n')) {
+    for (auto& line : StringView(res.value().output).split_view('\n')) {
         RegexResult result;
         if (!parse_library_definition.search(line, result))
             continue;
@@ -234,10 +234,10 @@ void ProjectBuilder::for_each_library_dependencies(Function<void(DeprecatedStrin
         warnln("{}", res.error());
         return;
     }
+    auto libraries = StringView(res.value().output).split_view('\n');
 
     static Regex<ECMA262> const parse_library_definition(R"~~~(.+:target_link_libraries\((\w+) ([\w\s]+)\).*)~~~");
-    for (auto& line : res.value().output.split('\n')) {
-
+    for (auto& line : libraries) {
         RegexResult result;
         if (!parse_library_definition.search(line, result))
             continue;

Userland/Libraries/LibCore/Command.cpp

@@ -7,7 +7,7 @@
 #include "Command.h"
 #include <AK/Format.h>
 #include <AK/ScopeGuard.h>
-#include <LibCore/DeprecatedFile.h>
+#include <LibCore/File.h>
 #include <fcntl.h>
 #include <stdio.h>
 #include <sys/wait.h>
@@ -72,16 +72,13 @@ ErrorOr<CommandResult> command(DeprecatedString const& program, Vector<Deprecate
     close(stdout_pipe[1]);
     close(stderr_pipe[1]);
 
-    auto read_all_from_pipe = [](int pipe[2]) {
-        auto result_file = Core::DeprecatedFile::construct();
-        if (!result_file->open(pipe[0], Core::OpenMode::ReadOnly, Core::DeprecatedFile::ShouldCloseFileDescriptor::Yes)) {
-            perror("open");
-            VERIFY_NOT_REACHED();
-        }
-        return DeprecatedString::copy(result_file->read_all());
+    auto read_all_from_pipe = [](int pipe[2]) -> ErrorOr<ByteBuffer> {
+        auto result_file_or_error = Core::File::adopt_fd(pipe[0], Core::File::OpenMode::Read, Core::File::ShouldCloseFileDescriptor::Yes);
+        auto result_file = TRY(result_file_or_error);
+        return result_file->read_until_eof();
     };
-    auto output = read_all_from_pipe(stdout_pipe);
-    auto error = read_all_from_pipe(stderr_pipe);
+    auto output = TRY(read_all_from_pipe(stdout_pipe));
+    auto error = TRY(read_all_from_pipe(stderr_pipe));
 
     int wstatus { 0 };
     waitpid(pid, &wstatus, 0);

Userland/Libraries/LibCore/Command.h

@@ -6,19 +6,18 @@
 
 #pragma once
 
-#include <AK/DeprecatedString.h>
+#include <AK/ByteBuffer.h>
 #include <AK/LexicalPath.h>
 #include <AK/Optional.h>
+#include <AK/String.h>
 #include <spawn.h>
 
 namespace Core {
 
-// If the executed command fails, the returned String will be in the null state.
-
 struct CommandResult {
     int exit_code { 0 };
-    DeprecatedString output;
-    DeprecatedString error;
+    ByteBuffer output;
+    ByteBuffer error;
 };
 
 ErrorOr<CommandResult> command(DeprecatedString const& program, Vector<DeprecatedString> const& arguments, Optional<LexicalPath> chdir);