CMP0053: document that `$` is a valid literal variable character

This was overlooked in the initial implementation of CMP0053. However,
an additional policy to reject it again is not worth it. Instead, add
tests and document the behavior.

Fixes: #17883

6 files changed, 41 insertions, 0 deletions

diff --git a/Tests/RunCMake/Syntax/CMP0053-Dollar-NEW-stderr.txt b/Tests/RunCMake/Syntax/CMP0053-Dollar-NEW-stderr.txt
new file mode 100644
index 0000000..7f248ae
--- /dev/null
+++ b/Tests/RunCMake/Syntax/CMP0053-Dollar-NEW-stderr.txt
@@ -0,0 +1,2 @@
+^-->value<--
+-->value<--$
diff --git a/Tests/RunCMake/Syntax/CMP0053-Dollar-NEW.cmake b/Tests/RunCMake/Syntax/CMP0053-Dollar-NEW.cmake
new file mode 100644
index 0000000..b81fd56
--- /dev/null
+++ b/Tests/RunCMake/Syntax/CMP0053-Dollar-NEW.cmake
@@ -0,0 +1,6 @@
+cmake_policy(SET CMP0053 NEW)
+
+set($ value)
+set(dollar $)
+message("-->${${dollar}}<--")
+message("-->${$}<--")
diff --git a/Tests/RunCMake/Syntax/CMP0053-Dollar-OLD-result.txt b/Tests/RunCMake/Syntax/CMP0053-Dollar-OLD-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/Syntax/CMP0053-Dollar-OLD-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/Syntax/CMP0053-Dollar-OLD-stderr.txt b/Tests/RunCMake/Syntax/CMP0053-Dollar-OLD-stderr.txt
new file mode 100644
index 0000000..aecd4d3
--- /dev/null
+++ b/Tests/RunCMake/Syntax/CMP0053-Dollar-OLD-stderr.txt
@@ -0,0 +1,24 @@
+^CMake Deprecation Warning at CMP0053-Dollar-OLD.cmake:1 \(cmake_policy\):
+  The OLD behavior for policy CMP0053 will be removed from a future version
+  of CMake.
+
+  The cmake-policies\(7\) manual explains that the OLD behaviors of all
+  policies are deprecated and that a policy should be set to OLD only under
+  specific short-term circumstances.  Projects should be ported to the NEW
+  behavior and not rely on setting a policy to OLD.
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
++
+-->value<--
+CMake Error at CMP0053-Dollar-OLD.cmake:6 \(message\):
+  Syntax error in cmake code at
+
+    .*CMP0053-Dollar-OLD.cmake:6
+
+  when parsing string
+
+    -->\${\$}<--
+
+  syntax error, unexpected \$, expecting } \(7\)
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)$
diff --git a/Tests/RunCMake/Syntax/CMP0053-Dollar-OLD.cmake b/Tests/RunCMake/Syntax/CMP0053-Dollar-OLD.cmake
new file mode 100644
index 0000000..647f464
--- /dev/null
+++ b/Tests/RunCMake/Syntax/CMP0053-Dollar-OLD.cmake
@@ -0,0 +1,6 @@
+cmake_policy(SET CMP0053 OLD)
+
+set($ value)
+set(dollar $)
+message("-->${${dollar}}<--")
+message("-->${$}<--")
diff --git a/Tests/RunCMake/Syntax/RunCMakeTest.cmake b/Tests/RunCMake/Syntax/RunCMakeTest.cmake
index a397620..8d74dc1 100644
--- a/Tests/RunCMake/Syntax/RunCMakeTest.cmake
+++ b/Tests/RunCMake/Syntax/RunCMakeTest.cmake
@@ -111,6 +111,8 @@ run_cmake(CMP0053-NameWithNewlineQuoted)
 run_cmake(CMP0053-NameWithCarriageReturnQuoted)
 run_cmake(CMP0053-NameWithEscapedSpacesQuoted)
 run_cmake(CMP0053-NameWithEscapedTabsQuoted)
+run_cmake(CMP0053-Dollar-OLD)
+run_cmake(CMP0053-Dollar-NEW)
 
 # Variable special types
 run_cmake(QueryCache)