Add lua helper functions to make it possible to automatically generate Obsoletes tags

python.lua

@@ -2,22 +2,25 @@
 
 -- Determine alternate names provided from the given name.
 -- Used in pythonname provides generator, python_provide and py_provides.
--- There are 2 rules:
+-- If only_3_to_3_X is false/nil/unused there are 2 rules:
 --  python3-foo  -> python-foo, python3.X-foo
 --  python3.X-foo -> python-foo, python3-foo
+-- If only_3_to_3_X is true there is only 1 rule:
+--  python3-foo  -> python3.X-foo
 -- There is no python-foo -> rule, python-foo packages are version agnostic.
 -- Returns a table/array with strings. Empty when no rule matched.
-local function python_altnames(name)
+local function python_altnames(name, only_3_to_3_X)
   local xy = rpm.expand('%{__default_python3_pkgversion}')
   local altnames = {}
   local replaced
   -- NB: dash needs to be escaped!
   if name:match('^python3%-') then
-    for i, prefix in ipairs({'python-', 'python' .. xy .. '-'}) do
+    local prefixes = only_3_to_3_X and {} or {'python-'}
+    for i, prefix in ipairs({'python' .. xy .. '-', table.unpack(prefixes)}) do
       replaced = name:gsub('^python3%-', prefix)
       table.insert(altnames, replaced)
     end
-  elseif name:match('^python' .. xy .. '%-') then
+  elseif name:match('^python' .. xy .. '%-') and not only_3_to_3_X then
     for i, prefix in ipairs({'python-', 'python3-'}) do
       replaced = name:gsub('^python' .. xy .. '%-', prefix)
       table.insert(altnames, replaced)
@@ -27,42 +30,72 @@ local function python_altnames(name)
 end
 
 
+local function __python_alttags(name, evr, tag_type)
+  -- for the "provides" tag_type we want also unversioned provides
+  local only_3_to_3_X = tag_type ~= "provides"
+  local operator = tag_type == "provides" and ' = ' or ' < '
+
+  -- global cache that tells what package NEVRs were already processed for the
+  -- given tag type
+  if __python_alttags_beenthere == nil then
+    __python_alttags_beenthere = {}
+  end
+  if __python_alttags_beenthere[tag_type] == nil then
+    __python_alttags_beenthere[tag_type] = {}
+  end
+  __python_alttags_beenthere[tag_type][name .. ' ' .. evr] = true
+  local alttags = {}
+  for i, altname in ipairs(python_altnames(name, only_3_to_3_X)) do
+    table.insert(alttags, altname .. operator .. evr)
+  end
+  return alttags
+end
+
 -- For any given name and epoch-version-release, return provides except self.
 -- Uses python_altnames under the hood
 -- Returns a table/array with strings.
 local function python_altprovides(name, evr)
-  -- global cache that tells what provides were already processed
-  if __python_altnames_provides_beenthere == nil then
-    __python_altnames_provides_beenthere = {}
-  end
-  __python_altnames_provides_beenthere[name .. ' ' .. evr] = true
-  local altprovides = {}
-  for i, altname in ipairs(python_altnames(name)) do
-    table.insert(altprovides, altname .. ' = ' .. evr)
-  end
-  return altprovides
+  return __python_alttags(name, evr, "provides")
 end
 
+-- For any given name and epoch-version-release, return versioned obsoletes except self.
+-- Uses python_altnames under the hood
+-- Returns a table/array with strings.
+local function python_altobsoletes(name, evr)
+  return __python_alttags(name, evr, "obsoletes")
+end
+
+
+local function __python_alttags_once(name, evr, tag_type)
+  -- global cache that tells what provides were already processed
+  if __python_alttags_beenthere == nil
+      or __python_alttags_beenthere[tag_type] == nil
+      or __python_alttags_beenthere[tag_type][name .. ' ' .. evr] == nil then
+    return __python_alttags(name, evr, tag_type)
+  else
+    return nil
+  end
+end
 
 -- Like python_altprovides but only return something once.
 -- For each argument can only be used once, returns nil otherwise.
 -- Previous usage of python_altprovides counts as well.
 local function python_altprovides_once(name, evr)
-  -- global cache that tells what provides were already processed
-  if __python_altnames_provides_beenthere == nil then
-    __python_altnames_provides_beenthere = {}
-  end
-  if __python_altnames_provides_beenthere[name .. ' ' .. evr] == nil then
-    __python_altnames_provides_beenthere[name .. ' ' .. evr] = true
-    return python_altprovides(name, evr)
-  else
-    return nil
-  end
+  return __python_alttags_once(name, evr, "provides")
+end
+
+-- Like python_altobsoletes but only return something once.
+-- For each argument can only be used once, returns nil otherwise.
+-- Previous usage of python_altobsoletes counts as well.
+local function python_altobsoletes_once(name, evr)
+  return __python_alttags_once(name, evr, "obsoletes")
 end
 
 
 return {
   python_altnames = python_altnames,
   python_altprovides = python_altprovides,
+  python_altobsoletes = python_altobsoletes,
   python_altprovides_once = python_altprovides_once,
+  python_altobsoletes_once = python_altobsoletes_once,
 }