Add PREPEND sub-command to string command

9 files changed, 108 insertions, 0 deletions

diff --git a/Help/command/string.rst b/Help/command/string.rst
index 4f0c45c..ba4a412 100644
--- a/Help/command/string.rst
+++ b/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
 """"""
 
diff --git a/Help/release/dev/string_prepend.rst b/Help/release/dev/string_prepend.rst
new file mode 100644
index 0000000..f896e91
--- /dev/null
+++ b/Help/release/dev/string_prepend.rst
@@ -0,0 +1,4 @@
+string_prepend
+--------------
+
+* The :command:`string` command learned a new ``PREPEND`` subcommand.
diff --git a/Source/cmStringCommand.cxx b/Source/cmStringCommand.cxx
index 5a6cf48..b07eae1 100644
--- a/Source/cmStringCommand.cxx
+++ b/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) {
diff --git a/Source/cmStringCommand.h b/Source/cmStringCommand.h
index 88015ad..0dded15 100644
--- a/Source/cmStringCommand.h
+++ b/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);
diff --git a/Tests/RunCMake/string/Prepend.cmake b/Tests/RunCMake/string/Prepend.cmake
new file mode 100644
index 0000000..8eaeebb
--- /dev/null
+++ b/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()
diff --git a/Tests/RunCMake/string/PrependNoArgs-result.txt b/Tests/RunCMake/string/PrependNoArgs-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/string/PrependNoArgs-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/string/PrependNoArgs-stderr.txt b/Tests/RunCMake/string/PrependNoArgs-stderr.txt
new file mode 100644
index 0000000..8d433f9
--- /dev/null
+++ b/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 \(include\)
diff --git a/Tests/RunCMake/string/PrependNoArgs.cmake b/Tests/RunCMake/string/PrependNoArgs.cmake
new file mode 100644
index 0000000..f324f28
--- /dev/null
+++ b/Tests/RunCMake/string/PrependNoArgs.cmake
@@ -0,0 +1 @@
+string(PREPEND)
diff --git a/Tests/RunCMake/string/RunCMakeTest.cmake b/Tests/RunCMake/string/RunCMakeTest.cmake
index 32b61b5..513d1e3 100644
--- a/Tests/RunCMake/string/RunCMakeTest.cmake
+++ b/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)