Recommend base::test::ScopedCommandLine usage.

base/command_line.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This class works with command lines: building and parsing.
 // Arguments with prefixes ('--', '-', and on Windows, '/') are switches.
 // Switches will precede all other arguments without switch prefixes.
 // Switches can optionally have values, delimited by '=', e.g., "-switch=value".
 // An argument of "--" will terminate switch parsing during initialization,
 // interpreting subsequent tokens as non-switch arguments, regardless of prefix.
@@ skipping 15 matching lines @@
 #include "build/build_config.h"
 
 namespace base {
 
 class FilePath;
 
 class BASE_EXPORT CommandLine {
  public:
 #if defined(OS_WIN)
   // The native command line string type.
-  typedef base::string16 StringType;
+  using StringType = string16;
 #elif defined(OS_POSIX)
-  typedef std::string StringType;
+  using StringType = std::string;
 #endif
 
-  typedef StringType::value_type CharType;
-  typedef std::vector<StringType> StringVector;
-  typedef std::map<std::string, StringType> SwitchMap;
-  typedef std::map<base::StringPiece, const StringType*> StringPieceSwitchMap;
+  using CharType = StringType::value_type;
+  using StringVector = std::vector<StringType>;
+  using SwitchMap = std::map<std::string, StringType>;
+  using StringPieceSwitchMap = std::map<StringPiece, const StringType*>;
 
   // A constructor for CommandLines that only carry switches and arguments.
   enum NoProgram { NO_PROGRAM };
   explicit CommandLine(NoProgram no_program);
 
   // Construct a new command line with |program| as argv[0].
   explicit CommandLine(const FilePath& program);
 
   // Construct a new command line from an argument list.
   CommandLine(int argc, const CharType* const* argv);
@@ skipping 28 matching lines @@
   // don't trust the CRT's parsing of the command line, but it still must be
   // called to set up the command line. Returns false if initialization has
   // already occurred, and true otherwise. Only the caller receiving a 'true'
   // return value should take responsibility for calling Reset.
   static bool Init(int argc, const char* const* argv);
 
   // Destroys the current process CommandLine singleton. This is necessary if
   // you want to reset the base library to its initial state (for example, in an
   // outer library that needs to be able to terminate, and be re-initialized).
   // If Init is called only once, as in main(), Reset() is not necessary.
+  // Do not call this in tests. Use base::test::ScopedCommandLine instead.
   static void Reset();
 
   // Get the singleton CommandLine representing the current process's
   // command line. Note: returned value is mutable, but not thread safe;
   // only mutate if you know what you're doing!
   static CommandLine* ForCurrentProcess();
 
   // Returns true if the CommandLine has been initialized for the given process.
   static bool InitializedForCurrentProcess();
 
 #if defined(OS_WIN)
-  static CommandLine FromString(const base::string16& command_line);
+  static CommandLine FromString(const string16& command_line);
 #endif
 
   // Initialize from an argv vector.
   void InitFromArgv(int argc, const CharType* const* argv);
   void InitFromArgv(const StringVector& argv);
 
   // Constructs and returns the represented command line string.
   // CAUTION! This should be avoided on POSIX because quoting behavior is
   // unclear.
   StringType GetCommandLineString() const {
@@ skipping 37 matching lines @@
 
   // Get and Set the program part of the command line string (the first item).
   FilePath GetProgram() const;
   void SetProgram(const FilePath& program);
 
   // Returns true if this command line contains the given switch.
   // Switch names must be lowercase.
   // The second override provides an optimized version to avoid inlining codegen
   // at every callsite to find the length of the constant and construct a
   // StringPiece.
-  bool HasSwitch(const base::StringPiece& switch_string) const;
+  bool HasSwitch(const StringPiece& switch_string) const;

[Lei Zhang, 2016/07/14 10:24:22]

Shall we pass these by value while we are here?

[Mark Mentovai, 2016/07/14 14:24:02]

Lei Zhang (Slow Thursday) wrote:
How would that help?

[Lei Zhang, 2016/07/15 00:44:39]

base::StringPiece (and base::Time) says to prefer passing by value, but others
pass by ref for consistency. Not sure if you had a strong opinion on this.

   bool HasSwitch(const char switch_constant[]) const;
 
   // Returns the value associated with the given switch. If the switch has no
   // value or isn't present, this method returns the empty string.
   // Switch names must be lowercase.
-  std::string GetSwitchValueASCII(const base::StringPiece& switch_string) const;
-  FilePath GetSwitchValuePath(const base::StringPiece& switch_string) const;
-  StringType GetSwitchValueNative(const base::StringPiece& switch_string) const;
+  std::string GetSwitchValueASCII(const StringPiece& switch_string) const;
+  FilePath GetSwitchValuePath(const StringPiece& switch_string) const;
+  StringType GetSwitchValueNative(const StringPiece& switch_string) const;
 
   // Get a copy of all switches, along with their values.
   const SwitchMap& GetSwitches() const { return switches_; }
 
   // Append a switch [with optional value] to the command line.
   // Note: Switches will precede arguments regardless of appending order.
   void AppendSwitch(const std::string& switch_string);
   void AppendSwitchPath(const std::string& switch_string,
                         const FilePath& path);
   void AppendSwitchNative(const std::string& switch_string,
@@ skipping 22 matching lines @@
   // If |include_program| is true, include |other|'s program as well.
   void AppendArguments(const CommandLine& other, bool include_program);
 
   // Insert a command before the current command.
   // Common for debuggers, like "valgrind" or "gdb --args".
   void PrependWrapper(const StringType& wrapper);
 
 #if defined(OS_WIN)
   // Initialize by parsing the given command line string.
   // The program name is assumed to be the first item in the string.
-  void ParseFromString(const base::string16& command_line);
+  void ParseFromString(const string16& command_line);
 #endif
 
  private:
   // Disallow default constructor; a program name must be explicitly specified.
   CommandLine();
   // Allow the copy constructor. A common pattern is to copy of the current
   // process's command line and then add some flags to it. For example:
   //   CommandLine cl(*CommandLine::ForCurrentProcess());
   //   cl.AppendSwitch(...);
 
@@ skipping 25 matching lines @@
   // Used for allocation-free lookups.
   StringPieceSwitchMap switches_by_stringpiece_;
 
   // The index after the program and switches, any arguments start here.
   size_t begin_args_;
 };
 
 }  // namespace base
 
 #endif  // BASE_COMMAND_LINE_H_