Add PREPEND sub-command to string command

Help/command/string.rst

@@ -132,6 +132,15 @@ APPEND
 
 Append all the input arguments to the string.
 
+PREPEND
+"""""""
+
+::
+
+  string(PREPEND <string variable> [<input>...])
+
+Prepend all the input arguments to the string.
+
 CONCAT
 """"""
 

Help/release/dev/string_prepend.rst

@@ -0,0 +1,4 @@
+string_prepend
+--------------
+
+* The :command:`string` command learned a new ``PREPEND`` subcommand.

Source/cmStringCommand.cxx

@@ -62,6 +62,9 @@ bool cmStringCommand::InitialPass(std::vector<std::string> const& args,
   if (subCommand == "APPEND") {
     return this->HandleAppendCommand(args);
   }
+  if (subCommand == "PREPEND") {
+    return this->HandlePrependCommand(args);
+  }
   if (subCommand == "CONCAT") {
     return this->HandleConcatCommand(args);
   }
@@ -643,6 +646,30 @@ bool cmStringCommand::HandleAppendCommand(std::vector<std::string> const& args)
   return true;
 }
 
+bool cmStringCommand::HandlePrependCommand(
+  std::vector<std::string> const& args)
+{
+  if (args.size() < 2) {
+    this->SetError("sub-command PREPEND requires at least one argument.");
+    return false;
+  }
+
+  // Skip if nothing to prepend.
+  if (args.size() < 3) {
+    return true;
+  }
+
+  const std::string& variable = args[1];
+
+  std::string value = cmJoin(cmMakeRange(args).advance(2), std::string());
+  const char* oldValue = this->Makefile->GetDefinition(variable);
+  if (oldValue) {
+    value += oldValue;
+  }
+  this->Makefile->AddDefinition(variable, value.c_str());
+  return true;
+}
+
 bool cmStringCommand::HandleConcatCommand(std::vector<std::string> const& args)
 {
   if (args.size() < 2) {

Source/cmStringCommand.h

@@ -46,6 +46,7 @@ protected:
   bool HandleLengthCommand(std::vector<std::string> const& args);
   bool HandleSubstringCommand(std::vector<std::string> const& args);
   bool HandleAppendCommand(std::vector<std::string> const& args);
+  bool HandlePrependCommand(std::vector<std::string> const& args);
   bool HandleConcatCommand(std::vector<std::string> const& args);
   bool HandleStripCommand(std::vector<std::string> const& args);
   bool HandleRandomCommand(std::vector<std::string> const& args);

Tests/RunCMake/string/Prepend.cmake

@@ -0,0 +1,58 @@
+set(out)
+string(PREPEND out)
+if(DEFINED out)
+  message(FATAL_ERROR "\"string(PREPEND out)\" set out to \"${out}\"")
+endif()
+
+set(out "")
+string(PREPEND out)
+if(NOT out STREQUAL "")
+  message(FATAL_ERROR "\"string(PREPEND out)\" set out to \"${out}\"")
+endif()
+
+set(out x)
+string(PREPEND out)
+if(NOT out STREQUAL "x")
+  message(FATAL_ERROR "\"string(PREPEND out)\" set out to \"${out}\"")
+endif()
+
+
+set(out)
+string(PREPEND out a)
+if(NOT out STREQUAL "a")
+  message(FATAL_ERROR "\"string(PREPEND out a)\" set out to \"${out}\"")
+endif()
+
+set(out "")
+string(PREPEND out a)
+if(NOT out STREQUAL "a")
+  message(FATAL_ERROR "\"string(PREPEND out a)\" set out to \"${out}\"")
+endif()
+
+set(out x)
+string(PREPEND out a)
+if(NOT out STREQUAL "ax")
+  message(FATAL_ERROR "\"string(PREPEND out a)\" set out to \"${out}\"")
+endif()
+
+
+set(out x)
+string(PREPEND out a "b")
+if(NOT out STREQUAL "abx")
+  message(FATAL_ERROR "\"string(PREPEND out a \"b\")\" set out to \"${out}\"")
+endif()
+
+set(b)
+set(out x)
+string(PREPEND out ${b})
+if(NOT out STREQUAL "x")
+  message(FATAL_ERROR "\"string(PREPEND out \${b})\" set out to \"${out}\"")
+endif()
+
+set(b b)
+set(out x)
+string(PREPEND out a "${b}" [[
+${c}]])
+if(NOT out STREQUAL "ab\${c}x")
+  message(FATAL_ERROR "\"string(PREPEND out a \"\${b}\" [[\${c}]])\" set out to \"${out}\"")
+endif()

Tests/RunCMake/string/PrependNoArgs-result.txt

@@ -0,0 +1 @@
+1

Tests/RunCMake/string/PrependNoArgs-stderr.txt

@@ -0,0 +1,4 @@
+CMake Error at PrependNoArgs.cmake:1 \(string\):
+  string sub-command PREPEND requires at least one argument.
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)

Tests/RunCMake/string/PrependNoArgs.cmake

@@ -0,0 +1 @@
+string(PREPEND)

Tests/RunCMake/string/RunCMakeTest.cmake

@@ -3,6 +3,9 @@ include(RunCMake)
 run_cmake(Append)
 run_cmake(AppendNoArgs)
 
+run_cmake(Prepend)
+run_cmake(PrependNoArgs)
+
 run_cmake(Concat)
 run_cmake(ConcatNoArgs)