cmake_minimum_required: Optionally set policies with version range

Teach `cmake_minimum_required` and `cmake_policy(VERSION)` to support a
version range of the form `<min>[...<max>]`.  Define this to mean that
version `<min>` is required, but known policies up to those introduced
by `<max>` will be set to `NEW`.  This will allow projects to easily
specify a range of versions for which they have been updated.

8 files changed, 88 insertions, 15 deletions

diff --git a/Source/CPack/cmCPackGenerator.cxx b/Source/CPack/cmCPackGenerator.cxx
index d41a9e5..64aba10 100644
--- a/Source/CPack/cmCPackGenerator.cxx
+++ b/Source/CPack/cmCPackGenerator.cxx
@@ -1002,7 +1002,8 @@ int cmCPackGenerator::DoPackage()
   { // scope that enables package generators to run internal scripts with
     // latest CMake policies enabled
     cmMakefile::ScopePushPop pp{ this->MakefileMap };
-    this->MakefileMap->SetPolicyVersion(cmVersion::GetCMakeVersion());
+    this->MakefileMap->SetPolicyVersion(cmVersion::GetCMakeVersion(),
+                                        std::string());
 
     if (!this->PackageFiles() || cmSystemTools::GetErrorOccuredFlag()) {
       cmCPackLogger(cmCPackLog::LOG_ERROR, "Problem compressing the directory"
diff --git a/Source/cmCMakeMinimumRequired.cxx b/Source/cmCMakeMinimumRequired.cxx
index bcc41fc..c4834a8 100644
--- a/Source/cmCMakeMinimumRequired.cxx
+++ b/Source/cmCMakeMinimumRequired.cxx
@@ -45,9 +45,24 @@ bool cmCMakeMinimumRequired::InitialPass(std::vector<std::string> const& args,
     return this->EnforceUnknownArguments();
   }
 
+  // Separate the <min> version and any trailing ...<max> component.
+  std::string::size_type const dd = version_string.find("...");
+  std::string const version_min = version_string.substr(0, dd);
+  std::string const version_max = dd != std::string::npos
+    ? version_string.substr(dd + 3, std::string::npos)
+    : std::string();
+  if (dd != std::string::npos &&
+      (version_min.empty() || version_max.empty())) {
+    std::ostringstream e;
+    e << "VERSION \"" << version_string
+      << "\" does not have a version on both sides of \"...\".";
+    this->SetError(e.str());
+    return false;
+  }
+
   // Save the required version string.
   this->Makefile->AddDefinition("CMAKE_MINIMUM_REQUIRED_VERSION",
-                                version_string.c_str());
+                                version_min.c_str());
 
   // Get the current version number.
   unsigned int current_major = cmVersion::GetMajorVersion();
@@ -61,10 +76,10 @@ bool cmCMakeMinimumRequired::InitialPass(std::vector<std::string> const& args,
   unsigned int required_minor = 0;
   unsigned int required_patch = 0;
   unsigned int required_tweak = 0;
-  if (sscanf(version_string.c_str(), "%u.%u.%u.%u", &required_major,
+  if (sscanf(version_min.c_str(), "%u.%u.%u.%u", &required_major,
              &required_minor, &required_patch, &required_tweak) < 2) {
     std::ostringstream e;
-    e << "could not parse VERSION \"" << version_string << "\".";
+    e << "could not parse VERSION \"" << version_min << "\".";
     this->SetError(e.str());
     return false;
   }
@@ -78,7 +93,7 @@ bool cmCMakeMinimumRequired::InitialPass(std::vector<std::string> const& args,
        current_patch == required_patch && current_tweak < required_tweak)) {
     // The current version is too low.
     std::ostringstream e;
-    e << "CMake " << version_string
+    e << "CMake " << version_min
       << " or higher is required.  You are running version "
       << cmVersion::GetCMakeVersion();
     this->Makefile->IssueMessage(cmake::FATAL_ERROR, e.str());
@@ -95,9 +110,9 @@ bool cmCMakeMinimumRequired::InitialPass(std::vector<std::string> const& args,
     this->Makefile->IssueMessage(
       cmake::AUTHOR_WARNING,
       "Compatibility with CMake < 2.4 is not supported by CMake >= 3.0.");
-    this->Makefile->SetPolicyVersion("2.4");
+    this->Makefile->SetPolicyVersion("2.4", version_max);
   } else {
-    this->Makefile->SetPolicyVersion(version_string.c_str());
+    this->Makefile->SetPolicyVersion(version_min, version_max);
   }
 
   return true;
diff --git a/Source/cmCMakePolicyCommand.cxx b/Source/cmCMakePolicyCommand.cxx
index 3ccc815..7ca1cbc 100644
--- a/Source/cmCMakePolicyCommand.cxx
+++ b/Source/cmCMakePolicyCommand.cxx
@@ -156,6 +156,23 @@ bool cmCMakePolicyCommand::HandleVersionMode(
     this->SetError("VERSION given too many arguments");
     return false;
   }
-  this->Makefile->SetPolicyVersion(args[1].c_str());
+  std::string const& version_string = args[1];
+
+  // Separate the <min> version and any trailing ...<max> component.
+  std::string::size_type const dd = version_string.find("...");
+  std::string const version_min = version_string.substr(0, dd);
+  std::string const version_max = dd != std::string::npos
+    ? version_string.substr(dd + 3, std::string::npos)
+    : std::string();
+  if (dd != std::string::npos &&
+      (version_min.empty() || version_max.empty())) {
+    std::ostringstream e;
+    e << "VERSION \"" << version_string
+      << "\" does not have a version on both sides of \"...\".";
+    this->SetError(e.str());
+    return false;
+  }
+
+  this->Makefile->SetPolicyVersion(version_min, version_max);
   return true;
 }
diff --git a/Source/cmMakefile.cxx b/Source/cmMakefile.cxx
index 23883f7..92d7681 100644
--- a/Source/cmMakefile.cxx
+++ b/Source/cmMakefile.cxx
@@ -1464,7 +1464,7 @@ void cmMakefile::Configure()
         this->SetCheckCMP0000(true);
 
         // Implicitly set the version for the user.
-        this->SetPolicyVersion("2.4");
+        this->SetPolicyVersion("2.4", std::string());
       }
     }
     bool hasProject = false;
@@ -4149,9 +4149,10 @@ void cmMakefile::PopSnapshot(bool reportError)
   assert(this->StateSnapshot.IsValid());
 }
 
-bool cmMakefile::SetPolicyVersion(std::string const& version_min)
+bool cmMakefile::SetPolicyVersion(std::string const& version_min,
+                                  std::string const& version_max)
 {
-  return cmPolicies::ApplyPolicyVersion(this, version_min);
+  return cmPolicies::ApplyPolicyVersion(this, version_min, version_max);
 }
 
 bool cmMakefile::HasCMP0054AlreadyBeenReported(
diff --git a/Source/cmMakefile.h b/Source/cmMakefile.h
index e90cf2f..414c08c 100644
--- a/Source/cmMakefile.h
+++ b/Source/cmMakefile.h
@@ -285,7 +285,8 @@ public:
   bool SetPolicy(cmPolicies::PolicyID id, cmPolicies::PolicyStatus status);
   bool SetPolicy(const char* id, cmPolicies::PolicyStatus status);
   cmPolicies::PolicyStatus GetPolicyStatus(cmPolicies::PolicyID id) const;
-  bool SetPolicyVersion(std::string const& version_min);
+  bool SetPolicyVersion(std::string const& version_min,
+                        std::string const& version_max);
   void RecordPolicies(cmPolicies::PolicyMap& pm);
   //@}
 
diff --git a/Source/cmPolicies.cxx b/Source/cmPolicies.cxx
index cf61edd..dba22b3 100644
--- a/Source/cmPolicies.cxx
+++ b/Source/cmPolicies.cxx
@@ -154,7 +154,8 @@ static bool GetPolicyDefault(cmMakefile* mf, std::string const& policy,
 }
 
 bool cmPolicies::ApplyPolicyVersion(cmMakefile* mf,
-                                    std::string const& version_min)
+                                    std::string const& version_min,
+                                    std::string const& version_max)
 {
   // Parse components of the minimum version.
   unsigned int minMajor = 2;
@@ -205,6 +206,42 @@ bool cmPolicies::ApplyPolicyVersion(cmMakefile* mf,
   unsigned int polMajor = minMajor;
   unsigned int polMinor = minMinor;
   unsigned int polPatch = minPatch;
+
+  if (!version_max.empty()) {
+    // Parse components of the maximum version.
+    unsigned int maxMajor = 0;
+    unsigned int maxMinor = 0;
+    unsigned int maxPatch = 0;
+    unsigned int maxTweak = 0;
+    if (sscanf(version_max.c_str(), "%u.%u.%u.%u", &maxMajor, &maxMinor,
+               &maxPatch, &maxTweak) < 2) {
+      std::ostringstream e;
+      e << "Invalid policy max version value \"" << version_max << "\".  "
+        << "A numeric major.minor[.patch[.tweak]] must be given.";
+      mf->IssueMessage(cmake::FATAL_ERROR, e.str());
+      return false;
+    }
+
+    // It is an error if the min version is greater than the max version.
+    if (minMajor > maxMajor || (minMajor == maxMajor && minMinor > maxMinor) ||
+        (minMajor == maxMajor && minMinor == maxMinor &&
+         minPatch > maxPatch) ||
+        (minMajor == maxMajor && minMinor == maxMinor &&
+         minPatch == maxPatch && minTweak > maxTweak)) {
+      std::ostringstream e;
+      e << "Policy VERSION range \"" << version_min << "..." << version_max
+        << "\""
+        << " specifies a larger minimum than maximum.";
+      mf->IssueMessage(cmake::FATAL_ERROR, e.str());
+      return false;
+    }
+
+    // Use the max version as the policy version.
+    polMajor = maxMajor;
+    polMinor = maxMinor;
+    polPatch = maxPatch;
+  }
+
   return cmPolicies::ApplyPolicyVersion(mf, polMajor, polMinor, polPatch);
 }
 
diff --git a/Source/cmPolicies.h b/Source/cmPolicies.h
index 00f3fd0..33896fe 100644
--- a/Source/cmPolicies.h
+++ b/Source/cmPolicies.h
@@ -289,7 +289,8 @@ public:
 
   ///! Set a policy level for this listfile
   static bool ApplyPolicyVersion(cmMakefile* mf,
-                                 std::string const& version_min);
+                                 std::string const& version_min,
+                                 std::string const& version_max);
   static bool ApplyPolicyVersion(cmMakefile* mf, unsigned int majorVer,
                                  unsigned int minorVer, unsigned int patchVer);
 
diff --git a/Source/cmQtAutoGenerator.cxx b/Source/cmQtAutoGenerator.cxx
index 1939bd4..5c35d76 100644
--- a/Source/cmQtAutoGenerator.cxx
+++ b/Source/cmQtAutoGenerator.cxx
@@ -612,7 +612,7 @@ bool cmQtAutoGenerator::Run(std::string const& infoFile,
     auto makefile = cm::make_unique<cmMakefile>(&gg, snapshot);
     // The OLD/WARN behavior for policy CMP0053 caused a speed regression.
     // https://gitlab.kitware.com/cmake/cmake/issues/17570
-    makefile->SetPolicyVersion("3.9");
+    makefile->SetPolicyVersion("3.9", std::string());
     gg.SetCurrentMakefile(makefile.get());
     success = this->Init(makefile.get());
   }