From 5d98731c656463d0ec49271efc2fc837e8b5ca6d Mon Sep 17 00:00:00 2001
From: Jason Perkins <starkos@industriousone.com>
Date: Mon, 22 Jun 2015 15:35:20 -0400
Subject: [PATCH] Add optional `versions` argument to require()

---
 src/base/_foundation.lua     | 10 ++++++++++
 src/base/globals.lua         | 26 ++++++++++++++++++++++++++
 src/host/premake.c           |  2 +-
 tests/base/test_versions.lua |  8 ++++++++
 4 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/src/base/_foundation.lua b/src/base/_foundation.lua
index 87ca2204..8cf1bfda 100644
--- a/src/base/_foundation.lua
+++ b/src/base/_foundation.lua
@@ -4,6 +4,9 @@
 ---
 
 	premake = premake or {}
+	premake._VERSION = _PREMAKE_VERSION
+	package.loaded["premake"] = premake
+
 	premake.modules = {}
 	premake.extensions = premake.modules
 
@@ -101,6 +104,10 @@
 ---
 
 	function p.checkVersion(version, checks)
+		if not version then
+			return false
+		end
+
 		local function parse(str)
 			local major, minor, patch, dev = str:match("^(%d+)%.?(%d*)%.?(%d*)(.-)$")
 			major = tonumber(major) or 0
@@ -142,6 +149,9 @@
 			elseif check:startswith("<") then
 				func = lt
 				check = check:sub(2)
+			elseif check:startswith("=") then
+				func = eq
+				check = check:sub(2)
 			else
 				func = ge
 			end
diff --git a/src/base/globals.lua b/src/base/globals.lua
index 8118ff68..89911b57 100644
--- a/src/base/globals.lua
+++ b/src/base/globals.lua
@@ -55,3 +55,29 @@
 			return dofile(fname)
 		end
 	end
+
+
+
+---
+-- Extend require() with a second argument to specify the expected
+-- version of the loaded module. Raises an error if the version criteria
+-- are not met.
+--
+-- @param modname
+--    The name of the module to load.
+-- @param versions
+--    An optional version criteria string; see premake.checkVersion()
+--    for more information on the format.
+-- @return
+--    If successful, the loaded module, which is also stored into the
+--    global package.loaded table.
+---
+
+	premake.override(_G, "require", function(base, modname, versions)
+		local mod = base(modname)
+		if mod and versions and not premake.checkVersion(mod._VERSION, versions) then
+			error(string.format("module %s %s does not meet version criteria %s",
+				modname, mod._VERSION or "(none)", versions), 3)
+		end
+		return mod
+	end)
diff --git a/src/host/premake.c b/src/host/premake.c
index 422b568d..593e1a71 100644
--- a/src/host/premake.c
+++ b/src/host/premake.c
@@ -14,7 +14,7 @@
 #endif
 
 
-#define VERSION        "HEAD"
+#define VERSION        "5.0.0-dev"
 #define COPYRIGHT      "Copyright (C) 2002-2015 Jason Perkins and the Premake Project"
 #define PROJECT_URL    "https://github.com/premake/premake-core/wiki"
 #define ERROR_MESSAGE  "Error: %s\n"
diff --git a/tests/base/test_versions.lua b/tests/base/test_versions.lua
index a2ef7e4d..c7475bc9 100644
--- a/tests/base/test_versions.lua
+++ b/tests/base/test_versions.lua
@@ -169,3 +169,11 @@
 		test.isfalse(p.checkVersion("2.2.0.0", ">=1.0 <2.0"))
 	end
 
+
+--
+-- If there is no version information, fails.
+--
+
+	function suite.fail_onNoVersion()
+		test.isfalse(p.checkVersion(nil, "1.0"))
+	end