add all_of and any_of to compose multiple predicates

Author: atomicptr

README.md

@@ -42,6 +42,26 @@ end
 
 spec.valid(my_predicate, instance_of_type) -- true if condition is valid
 
+-- compose multiple predicates
+local bool_or_user = spec.any_of(spec.boolean, user_spec)
+
+spec.valid(bool_or_user, true) -- true
+spec.valid(bool_or_user, { name = "Alice", age = 30 }) -- true
+spec.valid(bool_or_user, { name = "Bob" }) -- false
+
+local has_name = spec.keys {
+    name = spec.string,
+}
+
+local has_age = spec.keys {
+    age = spec.number,
+}
+
+-- same as the previous user_spec
+local is_user = spec.all_of(has_name, has_age)
+
+spec.valid(is_user, { name = "Alice", age = 30 })
+
 -- some useful helper functions...
 
 -- conform returns the value if it conforms to the spec

spec.lua

@@ -66,6 +66,52 @@ function M.some(value)
     return value ~= nil
 end
 
+---Tests if all of predicates are valid
+---@param ... fun(value: any): boolean
+---@return fun(value: any): boolean
+function M.all_of(...)
+    local predicates = { ... }
+
+    for _, pred in ipairs(predicates) do
+        if type(pred) ~= "function" then
+            error "Spec must be a function (e.g. spec.keys for tables)"
+        end
+    end
+
+    return function(value)
+        for _, pred in ipairs(predicates) do
+            if not pred(value) then
+                return false
+            end
+        end
+
+        return true
+    end
+end
+
+---Tests if any of predicates is valid
+---@param ... fun(value: any): boolean
+---@return fun(value: any): boolean
+function M.any_of(...)
+    local predicates = { ... }
+
+    for _, pred in ipairs(predicates) do
+        if type(pred) ~= "function" then
+            error "Spec must be a function (e.g. spec.keys for tables)"
+        end
+    end
+
+    return function(value)
+        for _, pred in ipairs(predicates) do
+            if pred(value) then
+                return true
+            end
+        end
+
+        return false
+    end
+end
+
 ---Test if table matches a shape
 ---@param spec_map table<string, fun(value: any): boolean>
 ---@return fun(value: any): boolean

spec_test.lua

@@ -43,6 +43,23 @@ describe("spec.lua", function()
         assert.True(spec.some "Test")
     end)
 
+    it("spec.all_of", function()
+        assert.False(spec.valid(spec.all_of(spec.string, spec.number), nil))
+        assert.True(spec.valid(spec.all_of(spec.table, spec.some), { 1, 2 }))
+        assert.True(spec.valid(
+            spec.all_of(spec.table, function(value)
+                return #value >= 2
+            end),
+            { 1, 2, 3 }
+        ))
+    end)
+
+    it("spec.any_of", function()
+        assert.False(spec.valid(spec.any_of(spec.string, spec.number), nil))
+        assert.True(spec.valid(spec.any_of(spec.table, spec.some), { 1, 2 }))
+        assert.True(spec.valid(spec.any_of(spec.number, spec.string, spec.table), { 1, 2 }))
+    end)
+
     it("spec.keys", function()
         local user_spec = spec.keys {
             name = spec.string,