flow like the river

VISUALIZACION/node_modules/graphql/validation/rules/VariablesInAllowedPositionRule.mjs

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+import inspect from "../../jsutils/inspect.mjs";
+import { GraphQLError } from "../../error/GraphQLError.mjs";
+import { Kind } from "../../language/kinds.mjs";
+import { isNonNullType } from "../../type/definition.mjs";
+import { typeFromAST } from "../../utilities/typeFromAST.mjs";
+import { isTypeSubTypeOf } from "../../utilities/typeComparators.mjs";
+
+/**
+ * Variables passed to field arguments conform to type
+ */
+export function VariablesInAllowedPositionRule(context) {
+  var varDefMap = Object.create(null);
+  return {
+    OperationDefinition: {
+      enter: function enter() {
+        varDefMap = Object.create(null);
+      },
+      leave: function leave(operation) {
+        var usages = context.getRecursiveVariableUsages(operation);
+
+        for (var _i2 = 0; _i2 < usages.length; _i2++) {
+          var _ref2 = usages[_i2];
+          var node = _ref2.node;
+          var type = _ref2.type;
+          var defaultValue = _ref2.defaultValue;
+          var varName = node.name.value;
+          var varDef = varDefMap[varName];
+
+          if (varDef && type) {
+            // A var type is allowed if it is the same or more strict (e.g. is
+            // a subtype of) than the expected type. It can be more strict if
+            // the variable type is non-null when the expected type is nullable.
+            // If both are list types, the variable item type can be more strict
+            // than the expected item type (contravariant).
+            var schema = context.getSchema();
+            var varType = typeFromAST(schema, varDef.type);
+
+            if (varType && !allowedVariableUsage(schema, varType, varDef.defaultValue, type, defaultValue)) {
+              var varTypeStr = inspect(varType);
+              var typeStr = inspect(type);
+              context.reportError(new GraphQLError("Variable \"$".concat(varName, "\" of type \"").concat(varTypeStr, "\" used in position expecting type \"").concat(typeStr, "\"."), [varDef, node]));
+            }
+          }
+        }
+      }
+    },
+    VariableDefinition: function VariableDefinition(node) {
+      varDefMap[node.variable.name.value] = node;
+    }
+  };
+}
+/**
+ * Returns true if the variable is allowed in the location it was found,
+ * which includes considering if default values exist for either the variable
+ * or the location at which it is located.
+ */
+
+function allowedVariableUsage(schema, varType, varDefaultValue, locationType, locationDefaultValue) {
+  if (isNonNullType(locationType) && !isNonNullType(varType)) {
+    var hasNonNullVariableDefaultValue = varDefaultValue != null && varDefaultValue.kind !== Kind.NULL;
+    var hasLocationDefaultValue = locationDefaultValue !== undefined;
+
+    if (!hasNonNullVariableDefaultValue && !hasLocationDefaultValue) {
+      return false;
+    }
+
+    var nullableLocationType = locationType.ofType;
+    return isTypeSubTypeOf(schema, varType, nullableLocationType);
+  }
+
+  return isTypeSubTypeOf(schema, varType, locationType);
+}