Integrate expressions into GraphQL

Fixes #13.

Author: Totktonada

graphql/accessor_general.lua

@@ -14,6 +14,7 @@ local avro_helpers = require('graphql.avro_helpers')
 local db_schema_helpers = require('graphql.db_schema_helpers')
 local error_codes = require('graphql.error_codes')
 local statistics = require('graphql.statistics')
+local expressions = require('graphql.expressions')
 
 local check = utils.check
 local e = error_codes
@@ -762,16 +763,16 @@ local function validate_collections(collections, schemas)
     end
 end
 
---- Whether an object match set of PCRE.
----
---- @tparam table obj an object to check
+--- Whether an object match set of PCREs.
 ---
 --- @tparam table pcre map with PCRE as values; names are correspond to field
 --- names of the `obj` to match
 ---
+--- @tparam table obj an object to check
+---
 --- @treturn boolean `res` whether the `obj` object match `pcre` set of
 --- regexps.
-local function match_using_re(obj, pcre)
+local function match_using_re(pcre, obj)
     if pcre == nil then return true end
 
     assert(rex ~= nil, 'we should not pass over :compile() ' ..
@@ -784,7 +785,7 @@ local function match_using_re(obj, pcre)
             return false
         end
         if type(re) == 'table' then
-            local match = match_using_re(obj[field_name], re)
+            local match = match_using_re(re, obj[field_name])
             if not match then return false end
         elseif not utils.regexp(re, obj[field_name]) then
             return false
@@ -794,6 +795,24 @@ local function match_using_re(obj, pcre)
     return true
 end
 
+--- Whether an object match an expression.
+---
+--- @param expr (table or string) compiled or raw expression
+---
+--- @tparam table obj an object to check
+---
+--- @tparam[opt] table variables variables values from the request
+---
+--- @treturn boolean `res` whether the `obj` object match `expr` expression
+local function match_using_expr(expr, obj, variables)
+    if expr == nil then return true end
+
+    check(expr, 'expression', 'table')
+    local res = expr:execute(obj, variables)
+    check(res, 'expression result', 'boolean')
+    return res
+end
+
 --- Check whether we meet deadline time.
 ---
 --- The functions raises an exception in the case.
@@ -834,6 +853,7 @@ end
 --- * `pivot_filter` (table, set of fields to match the objected pointed by
 ---   `offset` arqument of the GraphQL query),
 --- * `resolveField` (function) for subrequests, see @{impl.new}.
+--- * XXX: describe other fields.
 ---
 --- @return nil
 ---
@@ -864,7 +884,9 @@ local function process_tuple(self, state, tuple, opts)
 
     local collection_name = opts.collection_name
     local pcre = opts.pcre
+    local expr = opts.expr
     local resolveField = opts.resolveField
+    local variables = qcontext.variables
 
     -- convert tuple -> object
     local obj = opts.unflatten_tuple(self, collection_name, tuple,
@@ -895,7 +917,7 @@ local function process_tuple(self, state, tuple, opts)
 
     -- filter out non-matching objects
     local match = utils.is_subtable(obj, truncated_filter) and
-        match_using_re(obj, pcre)
+        match_using_re(pcre, obj) and match_using_expr(expr, obj, variables)
     if do_filter then
         if not match then return true end
     else
@@ -1035,6 +1057,13 @@ local function prepare_select_internal(self, collection_name, from, filter,
         qcontext = qcontext
     }
 
+    -- compile an expression argument if provided and did not compiled yet
+    local expr = args.filter
+    check(expr, 'expression', 'table', 'string', 'nil')
+    if type(expr) == 'string' then
+        expr = expressions.new(expr)
+    end
+
     -- read only process_tuple options
     local select_opts = {
         limit = args.limit,
@@ -1046,6 +1075,7 @@ local function prepare_select_internal(self, collection_name, from, filter,
         use_tomap = self.collection_use_tomap[collection_name] or false,
         default_unflatten_tuple = default_unflatten_tuple,
         pcre = args.pcre,
+        expr = expr,
         resolveField = extra.resolveField,
         is_hidden = extra.is_hidden,
     }

graphql/core/rules.lua

@@ -415,6 +415,11 @@ function rules.variableDefaultValuesHaveCorrectType(node, context)
 end
 
 function rules.variablesAreUsed(node, context)
+  local operationName = node.name and node.name.value or ''
+  if context.skipVariableUseCheck[operationName] then
+    return
+  end
+
   if node.variableDefinitions then
     for _, definition in ipairs(node.variableDefinitions) do
       local variableName = definition.variable.name.value
@@ -605,3 +610,5 @@ end
 -- }}}
 
 return rules
+
+-- vim: set ts=2 sw=2 et:

graphql/core/util.lua

@@ -92,6 +92,11 @@ function util.coerceValue(node, schemaType, variables, opts)
     return nil
   end
 
+  -- handle precompiled values
+  if node.compiled ~= nil then
+    return node.compiled
+  end
+
   if node.kind == 'variable' then
     return variables[node.name.value]
   end

graphql/core/validate.lua

@@ -18,7 +18,7 @@ local function getParentField(context, name, count)
   return parent.fields[name]
 end
 
-local visitors = {
+local defaultVisitors = {
   -- <document>
   --
   -- {
@@ -467,7 +467,7 @@ local visitors = {
   }
 }
 
-return function(schema, tree)
+return function(schema, tree, extraVisitors)
   local context = {
     schema = schema,
     fragmentMap = {},
@@ -476,41 +476,67 @@ return function(schema, tree)
     usedFragments = {},
     objects = {},
     currentOperation = nil,
-    variableReferences = nil
+    variableReferences = nil,
+    skipVariableUseCheck = {}, -- operation name -> boolean
   }
 
   local function visit(node)
-    local visitor = node.kind and visitors[node.kind]
+    local visitors = {}
+    visitors[#visitors + 1] = node.kind and defaultVisitors[node.kind]
+    visitors[#visitors + 1] = node.kind and extraVisitors[node.kind]
+
+    local enterList = {}
+    local ruleList = {}
+    local childrenList = {}
+    local exitRuleList = {}
+    local exitList = {}
+
+    -- collect visitors methods
+    for _, visitor in ipairs(visitors) do
+      enterList[#enterList + 1] = visitor.enter
+
+      if visitor.rules then
+        for _, rule in ipairs(visitor.rules) do
+          ruleList[#ruleList + 1] = rule
+        end
+      end
+
+      childrenList[#childrenList + 1] = visitor.children
+
+      if visitor.rules and visitor.rules.exit then
+        for _, exitRule in ipairs(visitor.rules.exit) do
+          exitRuleList[#exitRuleList + 1] = exitRule
+        end
+      end
+
+      exitList[#exitList + 1] = visitor.exit
+    end
 
-    if not visitor then return end
+    -- invoke visitors methods
 
-    if visitor.enter then
-      visitor.enter(node, context)
+    for _, enter in ipairs(enterList) do
+      enter(node, context)
     end
 
-    if visitor.rules then
-      for i = 1, #visitor.rules do
-        visitor.rules[i](node, context)
-      end
+    for _, rule in ipairs(ruleList) do
+      rule(node, context)
     end
 
-    if visitor.children then
-      local children = visitor.children(node)
-      if children then
-        for _, child in ipairs(children) do
+    for _, children in ipairs(childrenList) do
+      local childs = children(node)
+      if childs then
+        for _, child in ipairs(childs) do
           visit(child)
         end
       end
     end
 
-    if visitor.rules and visitor.rules.exit then
-      for i = 1, #visitor.rules.exit do
-        visitor.rules.exit[i](node, context)
-      end
+    for _, exitRule in ipairs(exitRuleList) do
+      exitRule(node, context)
     end
 
-    if visitor.exit then
-      visitor.exit(node, context)
+    for _, exit in ipairs(exitList) do
+      exit(node, context)
     end
   end
 

graphql/expressions.lua

@@ -1,11 +1,6 @@
 local lpeg = require('lulpeg')
 local utils = require('graphql.utils')
 
---- NOTE: Functions that worth moving out into other modules:
----       1) Regexp implementation (also lies inside of
----          accessor_general.lua)
----       2) Vararg iterator.
-
 --- TODO:
 ---     1) Validation.
 ---     2) Big numbers.

graphql/extend_ast.lua

@@ -0,0 +1,62 @@
+local expressions = require('graphql.expressions')
+
+local extend_ast = {}
+
+local function compile_filter_argument(node, context)
+    assert(node.kind == 'argument')
+    local argument_node = node
+    local argument_name = argument_node.name.value
+
+    if argument_name ~= 'filter' then return end
+
+    -- save compiled expression to <string> node
+    local value_node = argument_node.value
+    if value_node.kind == 'variable' then
+        -- a filter passed as a variable can use any other variables, so we disable
+        -- this check for the operation with such filter
+        local operation = context.currentOperation
+        local operation_name = operation.name and operation.name.value or ''
+        context.skipVariableUseCheck[operation_name] = true
+        return
+    end
+    assert(value_node.kind == 'string' and type(value_node.value) == 'string',
+        '"filter" list filtering argument must be a variable or a literal ' ..
+        'string')
+    local string_node = value_node
+    local value = string_node.value
+    local compiled_expr = expressions.new(value)
+    string_node.compiled = compiled_expr
+
+    -- XXX: don't blindly find the pattern {kind = 'variable', ...}, but either
+    -- traverse a tree according to node kinds or export used variables info
+    -- from expressions module
+
+    -- mark used variables
+    local open_set = {compiled_expr}
+    while true do
+        local e_node = table.remove(open_set, 1)
+        if e_node == nil then break end
+        if type(e_node) == 'table' then
+            if e_node.kind == 'variable' then
+                context.variableReferences[e_node.name] = true
+            else
+                for _, child_e_node in pairs(e_node) do
+                    table.insert(open_set, child_e_node)
+                end
+            end
+        end
+    end
+end
+
+--- Visitors to pass to validate.lua.
+function extend_ast.visitors()
+    return {
+        argument = {
+            rules = {
+                compile_filter_argument,
+            }
+        }
+    }
+end
+
+return extend_ast

graphql/gen_arguments.lua

@@ -348,7 +348,7 @@ function gen_arguments.list_args(db_schema, collection_name)
     return {
         {name = 'limit', type = 'int*'},
         {name = 'offset', type = offset_type},
-        -- {name = 'filter', type = ...},
+        {name = 'filter', type = 'string*'},
         pcre_field,
     }
 end

graphql/impl.lua

@@ -14,6 +14,7 @@ local simple_config = require('graphql.simple_config')
 local config_complement = require('graphql.config_complement')
 local server = require('graphql.server.server')
 local convert_schema = require('graphql.convert_schema')
+local extend_ast = require('graphql.extend_ast')
 
 local utils = require('graphql.utils')
 local check = utils.check
@@ -51,6 +52,7 @@ local function gql_execute(qstate, variables, operation_name)
 
     local qcontext = {
         query_settings = qstate.query_settings,
+        variables = variables,
     }
 
     local traceback
@@ -187,7 +189,7 @@ local function gql_compile(state, query, opts)
     local opts = opts or {}
 
     local ast = parse(query)
-    validate(state.schema, ast)
+    validate(state.schema, ast, extend_ast.visitors())
 
     local qstate = {
         state = state,

graphql/utils.lua

@@ -309,11 +309,11 @@ end
 
 --- Compare pattern with a string using pcre.
 ---
---- @param pattern matching pattern
+--- @tparam table pattern matching pattern
 ---
---- @param string  string to match
+--- @tparam string string to match
 ---
---- @return true or false
+--- @treturn boolean true or false
 function utils.regexp(pattern, string)
     local rex, is_pcre2 = utils.optional_require_rex()
     local flags = rex.flags()