rockspec: fix handling of rockspec_format versions

* luarocks/type_check.lua:
  * fix expansion of platforms
* luarocks/type/rockspec.lua:
  * when a version fails checking, try with a later
    version to produce a hint in the error message.

See #823.

2 files changed, 56 insertions, 31 deletions

diff --git a/src/luarocks/type/rockspec.lua b/src/luarocks/type/rockspec.lua
index 8b2bdffa..8214516e 100644
--- a/src/luarocks/type/rockspec.lua
+++ b/src/luarocks/type/rockspec.lua
@@ -17,7 +17,7 @@ type_rockspec.rockspec_format = "3.0"
 --    _more (boolean) indicates that the table accepts unspecified keys and does not type-check them.
 --    Any other string keys that don't start with an underscore represent known keys and are type-checking tables, recursively checked.
 
-local rockspec_formats = type_check.declare_schemas({
+local rockspec_formats, versions = type_check.declare_schemas({
    ["1.0"] = {
       rockspec_format = { _type = "string" },
       package = { _type = "string", _mandatory = true },
@@ -143,6 +143,22 @@ type_rockspec.order = {"rockspec_format", "package", "version",
    "test_dependencies", { "test", {"type"} },
    "hooks"}
 
+local function check_rockspec_using_version(rockspec, globals, version)
+   local schema = rockspec_formats[version]
+   if not schema then
+      return nil, "unknown rockspec format " .. version
+   end
+   local ok, err = type_check.check_undeclared_globals(globals, schema)
+   if ok then
+      ok, err = type_check.type_check_table(version, rockspec, schema, "")
+   end
+   if ok then
+      return true
+   else
+      return nil, err
+   end
+end
+
 --- Type check a rockspec table.
 -- Verify the correctness of elements from a 
 -- rockspec table, reporting on unknown fields and type
@@ -151,19 +167,33 @@ type_rockspec.order = {"rockspec_format", "package", "version",
 -- succeeded, or nil and an error message if it failed.
 function type_rockspec.check(rockspec, globals)
    assert(type(rockspec) == "table")
+
    local version = rockspec.rockspec_format or "1.0"
-   local schema = rockspec_formats[version]
-   if not schema then
-      return nil, "unknown rockspec format " .. version
-   end
-   local ok, err = type_check.check_undeclared_globals(globals, schema)
-   if ok then
-      ok, err = type_check.type_check_table(version, rockspec, schema, "")
-   end
+   local ok, err = check_rockspec_using_version(rockspec, globals, version)
    if ok then
       return true
    end
-   return nil, err .. " (rockspec format " .. version .. ")"
+
+   -- Rockspec parsing failed.
+   -- Let's see if it would pass using a later version.
+
+   local found = false
+   for _, v in ipairs(versions) do
+      if not found then
+         if v == version then
+            found = true
+         end
+      else
+         local v_ok, v_err = check_rockspec_using_version(rockspec, globals, v)
+         if v_ok then
+            return nil, err .. " (using rockspec format " .. version .. " -- " ..
+               [[adding 'rockspec_format = "]] .. v .. [["' to the rockspec ]] ..
+               [[will fix this)]]
+         end
+      end
+   end
+
+   return nil, err .. " (using rockspec format " .. version .. ")"
 end
 
 return type_rockspec
diff --git a/src/luarocks/type_check.lua b/src/luarocks/type_check.lua
index b204f5ee..bdf8ecc8 100644
--- a/src/luarocks/type_check.lua
+++ b/src/luarocks/type_check.lua
@@ -2,11 +2,14 @@
 local type_check = {}
 
 local cfg = require("luarocks.core.cfg")
-local vers = require("luarocks.core.vers")
+local fun = require("luarocks.fun")
 local util = require("luarocks.util")
+local vers = require("luarocks.core.vers")
 --------------------------------------------------------------------------------
 
-type_check.MAGIC_PLATFORMS = {}
+-- A magic constant that is not used anywhere in a schema definition
+-- and retains equality when the table is deep-copied.
+type_check.MAGIC_PLATFORMS = 0xEBABEFAC
 
 do
    local function fill_in_version(tbl, version)
@@ -26,7 +29,7 @@ do
             tbl[k] = {
                _any = util.deep_copy(tbl)
             }
-            tbl[k]._any[v] = nil
+            tbl[k]._any[k] = nil
          elseif type(v) == "table" then
             expand_magic_platforms(v)
          end
@@ -38,34 +41,26 @@ do
    -- and the value is a schema specification. Schema versions are considered
    -- incremental: version "2.0" only needs to specify what's new/changed from
    -- version "1.0".
-   function type_check.declare_schemas(versions)
+   function type_check.declare_schemas(inputs)
       local schemas = {}
       local parent_version
    
-      local version_list = {}
-      -- FIXME sorting lexicographically! "1.9" > "1.10"
-      for version, schema in util.sortedpairs(versions) do
-         table.insert(version_list, version)
+      local versions = fun.reverse_in(fun.sort_in(util.keys(inputs), vers.compare_versions))
+
+      for _, version in ipairs(versions) do
+         local schema = inputs[version]
          if parent_version ~= nil then
             local copy = util.deep_copy(schemas[parent_version])
             util.deep_merge(copy, schema)
-            schemas[version] = copy
-         else
-            schemas[version] = schema
+            schema = copy
          end
-         fill_in_version(schemas[version], version)
-         expand_magic_platforms(schemas[version])
+         fill_in_version(schema, version)
+         expand_magic_platforms(schema)
          parent_version = version
-      end
-      
-      -- Merge future versions as fallbacks under the old versions,
-      -- so that error messages can inform users when they try
-      -- to use new features without bumping rockspec_format in their rockspecs.
-      for i = #version_list, 2, -1 do
-         util.deep_merge_under(schemas[version_list[i - 1]], schemas[version_list[i]])
+         schemas[version] = schema
       end
 
-      return schemas
+      return schemas, versions
    end
 end