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lib/graphql_query.ex
defmodule GraphqlQuery do
@external_resource "README.md"
@moduledoc "README.md"
|> File.read!()
|> String.split("<!-- MDOC -->")
|> Enum.fetch!(1)
alias __MODULE__.{Parser, Document, Validator}
@doc """
Sets up the module to use GraphQL query macros and validation.
## Options
* `:schema` - Schema module implementing GraphqlQuery.Schema behaviour
* `:runtime` - Whether to validate queries at runtime (default: false)
* `:ignore` - Whether to ignore validation errors (default: false)
* `:evaluate` - Whether to try evaluating dynamic parts at compile time (default: false)
* `:fragments` - List of fragments to include in queries (default: [])
## Examples
defmodule MyApp.Queries do
use GraphqlQuery, schema: MyApp.Schema
def get_user do
~GQL"query { user { id name } }"
end
end
"""
defmacro __using__(opts) do
module = __CALLER__.module
schema = opts[:schema]
opts = validate_options!(Keyword.delete(opts, :schema))
if schema do
loaded_schema = ensure_module_loaded!(schema)
behaviours = get_module_behaviours(loaded_schema)
if GraphqlQuery.Schema not in behaviours do
raise ArgumentError,
"Schema module #{inspect(schema)} must implement GraphqlQuery.Schema behaviour"
end
end
Module.put_attribute(module, :__graphql_query__runtime, opts.runtime)
Module.put_attribute(module, :__graphql_query__ignore, opts.ignore)
Module.put_attribute(module, :__graphql_query__evaluate, opts.evaluate)
Module.put_attribute(module, :__graphql_query__schema, schema)
Module.put_attribute(module, :__graphql_query__fragments, opts.fragments)
quote do
import GraphqlQuery
end
end
defp get_module_behaviours(module) do
module.module_info()[:attributes]
|> Enum.filter(fn {k, _} -> k == :behaviour end)
|> Enum.flat_map(fn {_, behaviours} -> behaviours end)
end
@doc """
Applies GraphQL macro options to all GraphQL macros within a block.
This macro provides a convenient way to apply common options to multiple GraphQL
macros (`~GQL`, `gql`, `gql_from_file`) within a do block, but it's recommended to
apply it only for one.
The most important use case is enabling the `~GQL` sigil to work with complex
options like `:schema` and `:fragments`, which are not directly available through
sigil modifiers.
## Options
* `:type` - Document type (:query, :schema, :fragment) (default: :query)
* `:ignore` - Skip validation (default: false)
* `:runtime` - Validate at runtime instead of compile-time (default: false)
* `:evaluate` - Try to expand function calls at compile time (default: false)
* `:schema` - Schema module for validation (default: module schema if set)
* `:fragments` - List of fragments to include (default: [])
## Option Precedence
Options are merged with the following precedence (highest to lowest):
1. Explicit options on individual macros (e.g., `gql [ignore: false], "..."`)
2. Sigil modifiers (e.g., `~GQL"..."f` for fragment type)
3. Options from `document_with_options`
4. Module-level defaults from `use GraphqlQuery`
## Examples
### Basic Usage with Schema Validation
document_with_options schema: MySchema do
~GQL\"\"\"
query GetUser { user { ...UserFragment } }
\"\"\" # ✅ Schema validation applied
end
### Using Fragments
user_fragment = ~GQL\"\"\"
fragment UserFields on User {
id
name
email
}
\"\"\"f
document_with_options fragments: [user_fragment] do
~GQL\"\"\"
query GetUserWithFragment {
user {
...UserFields
}
}
\"\"\"
end
### Schema Validation for Multiple Documents (but set it in `use GraphqlQuery, schema: Schema` is prefered)
document_with_options schema: MyApp.Schema do
@user_query ~GQL\"\"\"
query GetUser($id: ID!) {
user(id: $id) { id name }
}
\"\"\"
@users_query ~GQL\"\"\"
query GetUsers {
users { id name }
}
\"\"\"
end
### Fragment Management
@user_fields ~GQL\"\"\"
fragment UserFields on User {
id name email
}
\"\"\"f
document_with_options fragments: [@user_fields] do
@get_user ~GQL\"\"\"
query GetUser { user { ...UserFields } }
\"\"\"
@get_users ~GQL\"\"\"
query GetUsers { users { ...UserFields } }
\"\"\"
end
## Integration Notes
This macro works by walking the AST of the provided block and transforming
all GraphqlQuery macro calls to include the specified options. It supports:
- `~GQL` sigil (adds options as third parameter)
- `gql/1` and `gql/2` macro calls
- `gql_from_file/1` and `gql_from_file/2` macro calls
- Nested expressions containing GraphqlQuery macros
- Multiple macro calls within the same block
The transformation happens at compile time, so there's no runtime overhead.
"""
defmacro document_with_options(opts, do: block) do
validate_options!(Keyword.delete(opts, :schema))
modified_block = Macro.prewalk(block, fn ast -> add_extra_opts_to_ast(ast, opts) end)
quote do
unquote(modified_block)
end
end
# This is used like:
# document_with_options ~GQL"", ignore: true
# But I don't really like this syntax, let's keep it commented out for now
# defmacro document_with_options(ast, opts) do
# validate_options!(opts)
# ast = add_extra_opts_to_ast(ast, opts)
# quote do
# unquote(ast)
# end
# end
defp add_extra_opts_to_ast(ast, extra_opts) do
case ast do
{:sigil_GQL, meta, [query, opts]} ->
{:sigil_GQL, meta, [query, opts, extra_opts]}
{:sigil_GQL, meta, [query, opts, current_extra_opts]} ->
new_opts = Keyword.merge(current_extra_opts, extra_opts)
{:sigil_GQL, meta, [query, opts, new_opts]}
{:gql, meta, [data]} ->
{:gql, meta, [extra_opts, data]}
{:gql, meta, [opts, data]} ->
new_opts = Keyword.merge(extra_opts, opts)
{:gql, meta, [new_opts, data]}
{:gql_from_file, meta, [data]} ->
{:gql_from_file, meta, [data, extra_opts]}
{:gql_from_file, meta, [data, opts]} ->
new_opts = Keyword.merge(extra_opts, opts)
{:gql_from_file, meta, [data, new_opts]}
other ->
other
end
end
@doc """
Loads and validates GraphQL queries from external files.
Automatically tracks file dependencies for recompilation and validates
the loaded content at compile time.
## Options
* `:type` - Document type (:query, :schema, :fragment) (default: :query)
* `:ignore` - Skip validation (default: false)
* `:schema` - Schema module for validation (default: module schema if set)
* `:fragments` - List of fragments to include (default: [])
## Examples
# Load a query file
query = gql_from_file("priv/queries/get_user.graphql")
# Load a fragment with schema validation
fragment = gql_from_file("priv/fragments/user.gql",
type: :fragment,
schema: MyApp.Schema)
# Load schema
schema = gql_from_file("priv/schema.graphql", type: :schema)
"""
defmacro gql_from_file(file_path, opts \\ []) do
Module.put_attribute(__CALLER__.module, :external_resource, file_path)
caller = __CALLER__
validate_options!(opts)
ignore? = get_option(opts, :ignore, false, caller)
runtime_validation? = get_option(opts, :runtime, false, caller)
type = get_option(opts, :type, :query, caller)
schema_module = get_schema_module(opts, caller)
fragments = get_option(opts, :fragments, [], caller)
fragments_evaluated = expand_fragments!(fragments, caller)
contents = File.read!(file_path)
warn_location = [file: file_path]
query_opts = [
path: file_path,
type: type,
schema: schema_module,
fragments: fragments_evaluated
]
query = Document.new(contents, query_opts)
cond do
ignore? ->
Macro.escape(query)
runtime_validation? ->
# Validate on runtime
query_opts = Keyword.put(query_opts, :fragments, fragments)
validate_on_runtime(contents, query_opts, warn_location)
true ->
do_validate(query, warn_location)
Macro.escape(query)
end
end
@doc """
Creates GraphQL documents with dynamic content and validation.
Supports both static and dynamic queries with compile-time validation.
Can expand module attributes and function calls when `evaluate: true` is set.
## Options
* `:type` - Document type (:query, :schema, :fragment) (default: :query)
* `:ignore` - Skip validation (default: false)
* `:runtime` - Validate at runtime instead of compile-time (default: false)
* `:evaluate` - Try to expand function calls at compile time (default: false)
* `:schema` - Schema module for validation (default: module schema if set)
* `:fragments` - List of fragments to include (default: [])
## Examples
# Static query with module attribute
@fields "id name email"
query = gql "query { user { \#{@fields} } }"
# Dynamic query with fragments
query = gql [fragments: [@user_fragment]], "query { user { ...UserFragment } }"
# Runtime validation for fully dynamic content
def build_query(field_list) do
gql [runtime: true], "query { user { \#{field_list} } }"
end
# Schema validation
query = gql [schema: MyApp.Schema], "query { user { id name } }"
"""
defmacro gql(opts \\ [], ast)
defmacro gql(opts, content) when is_binary(content) do
caller = __CALLER__
file = caller.file
warn_location = warn_location([], caller)
validate_options!(opts)
ignore? = get_option(opts, :ignore, false, caller)
runtime_validation? = get_option(opts, :runtime, false, caller)
schema_module = get_schema_module(opts, caller)
type = get_option(opts, :type, :query, caller)
fragments = get_option(opts, :fragments, [], caller)
fragments_evaluated = expand_fragments!(fragments, caller)
query_opts = [path: file, type: type, schema: schema_module, fragments: fragments_evaluated]
query = Document.new(content, query_opts)
cond do
ignore? ->
Macro.escape(query)
runtime_validation? ->
# Validate on runtime
query_opts = Keyword.put(query_opts, :fragments, fragments)
validate_on_runtime(content, query_opts, warn_location)
Enum.empty?(fragments) ->
IO.warn(
"""
[GraphqlQuery] GraphQL query is static.
Using the ~GQL sigil for static queries is recommended.
To disable this warning, use the [ignore: true] option.
""",
warn_location
)
do_validate(query, warn_location)
Macro.escape(query)
true ->
# fragments_evaluated = expand_fragments!(fragments, caller)
# query = Document.add_fragments(query, fragments_evaluated)
do_validate(query, warn_location)
Macro.escape(query)
end
end
defmacro gql(opts, {:<<>>, meta, parts} = original) do
# String with dynamic parts
do_gql(original, parts, __CALLER__, meta, opts)
end
defmacro gql(opts, {_, meta, _} = ast) do
# Method or module attribute call
do_gql(ast, [ast], __CALLER__, meta, opts)
end
defp do_gql(original, parts, caller, meta, opts) do
file = caller.file
validate_options!(opts)
warn_location = warn_location(meta, caller, -4)
evaluate? = get_option(opts, :evaluate, false, caller)
ignore? = get_option(opts, :ignore, false, caller)
runtime_validation? = get_option(opts, :runtime, false, caller)
schema_module = get_schema_module(opts, caller)
type = get_option(opts, :type, :query, caller)
fragments = get_option(opts, :fragments, [], caller)
fragments_evaluated = expand_fragments!(fragments, caller)
{static_parts, dynamic_parts} =
Enum.map_reduce(parts, [], fn
part, acc when is_binary(part) ->
# Static part, no need to expand
{part, acc}
ast, acc ->
case expand_until_string(ast, caller, evaluate?) do
{:ok, value} ->
# Successfully expanded to a string
{value, acc}
_ ->
# We can't expand it :(
{ast, acc ++ [ast]}
end
end)
has_dynamic_parts? = dynamic_parts != []
original_query_opts = [path: file, type: type, schema: schema_module, fragments: fragments]
original_query =
quote do
Document.new(unquote(original), unquote(original_query_opts))
end
query_opts = [path: file, type: type, schema: schema_module, fragments: fragments_evaluated]
cond do
ignore? ->
original_query
runtime_validation? ->
# Validate on runtime
query_opts = Keyword.put(query_opts, :fragments, fragments)
validate_on_runtime(original, query_opts, warn_location)
not has_dynamic_parts? ->
# Compile validation
compile_time_str = Enum.join(static_parts)
query =
Document.new(compile_time_str,
path: file,
type: type,
schema: schema_module,
fragments: fragments
)
do_validate(query, warn_location)
Macro.escape(query)
true ->
# We have dynamic parts, no runtime validation and we don't ignore it, so print a warning
Enum.each(dynamic_parts, fn expr ->
IO.warn(error_msg(expr, evaluate?), warn_location(expr, caller))
end)
original_query
end
end
@doc """
GraphQL sigil for static queries with compile-time validation.
Validates GraphQL queries, mutations, schemas, and fragments at compile time,
providing immediate feedback on syntax errors, unused variables, and schema violations.
Best suited for static GraphQL content without dynamic interpolation.
## Modifiers
The sigil supports several modifiers that can be combined:
* `i` - Ignore validation warnings
* `r` - Validate at runtime instead of compile-time
* `s` - Parse as schema document
* `q` - Parse as query document (default)
* `f` - Parse as fragment document
## Examples
### Basic Query
import GraphqlQuery
~GQL\"\"\"
query GetUser($id: ID!) {
user(id: $id) {
id
name
email
}
}
\"\"\"
### Schema Definition
~GQL\"\"\"
type User {
id: ID!
name: String!
email: String!
}
type Query {
user(id: ID!): User
}
\"\"\"s
### Fragment Definition
~GQL\"\"\"
fragment UserData on User {
id
name
email
}
\"\"\"f
### Ignoring Validation Warnings
# For queries with intentional unused variables
~GQL\"\"\"
query GetUser($id: ID!, $unused: String) {
user(id: $id) { name }
}
\"\"\"i
### Runtime Validation
# When fragments will be added later
~GQL\"\"\"
query GetUser($id: ID!) {
user(id: $id) {
...UserFragment
}
}
\"\"\"r |> GraphqlQuery.Document.add_fragment(user_fragment)
## Integration with Mix Format
The sigil integrates with `mix format` when the formatter plugin is configured:
# .formatter.exs
[
plugins: [GraphqlQuery.Formatter]
]
"""
defmacro sigil_GQL(data, opts) do
quote do
sigil_GQL(unquote(data), unquote(opts), [])
end
end
# credo:disable-for-next-line
defmacro sigil_GQL({:<<>>, meta, [query_string]}, opts, extra_opts) do
# Validate at compile time
caller = __CALLER__
file = caller.file
warn_location = warn_location(meta, caller)
ignore? =
if ?i in opts do
true
else
get_option(extra_opts, :ignore, false, caller)
end
runtime? =
if ?r in opts do
true
else
get_option(extra_opts, :runtime, false, caller)
end
type =
cond do
?s in opts ->
:schema
?q in opts ->
:query
?f in opts ->
:fragment
true ->
get_option(extra_opts, :type, :query, caller)
end
schema_module =
if module = get_option(extra_opts, :schema, nil, caller) do
ensure_module_loaded!(module)
else
nil
end
fragments = get_option(extra_opts, :fragments, [], caller)
fragments_evaluated = expand_fragments!(fragments, caller)
query_opts = [path: file, type: type, schema: schema_module, fragments: fragments_evaluated]
query = Document.new(query_string, query_opts)
cond do
ignore? ->
# If the ignore option is set, we skip validation
Macro.escape(query)
runtime? ->
# We want to validate on runtime anyway, maybe we'll add fragments later
query_opts = Keyword.put(query_opts, :fragments, fragments)
validate_on_runtime(query_string, query_opts, warn_location)
Parser.has_dynamic_parts?(to_string(query)) ->
msg = """
[GraphqlQuery] GraphQL query contains dynamic parts.
│
│ Use the "gql" macro instead to expand them and validate the query.
│
│ To disable this warning, use the `i` modifier: ~g"{}"#{opts}i
"""
IO.warn(msg, warn_location)
Macro.escape(query)
true ->
case Validator.validate(query) do
:ok ->
:ok
{:error, errors} ->
prefix =
"Validation errors, if you want to ignore them use the i modifier: ~G\"{}\"#{opts}i\n"
print_warnings(errors, warn_location, prefix)
end
Macro.escape(query)
end
end
defp warn_location(meta, caller, shift \\ 0)
defp warn_location({_, meta, _}, caller, shift), do: warn_location(meta, caller, shift)
defp warn_location(meta, %{line: line, file: file, function: function, module: module}, shift) do
line = if meta[:line], do: meta[:line], else: line
column = if column = meta[:column], do: column + shift
[line: line, function: function, module: module, file: file, column: column]
end
defp expand_until_string(ast, caller, evaluate?) do
ast
|> Macro.prewalker()
|> Enum.reduce_while(:error, fn
string, acc when is_binary(string) ->
# We went too far
{:halt, acc}
{:@, _, [{name, _, _}]}, acc ->
case get_module_attribute(caller.module, name) do
binary when is_binary(binary) ->
{:halt, {:ok, binary}}
%GraphqlQuery.Fragment{} = fragment ->
{:halt, {:ok, fragment}}
%GraphqlQuery.Document{} = document ->
{:halt, {:ok, to_string(document)}}
:undefined ->
{:halt, {:error, :module_attribute}}
_ ->
{:cont, acc}
end
expr, acc ->
case Macro.expand(expr, caller) do
string when is_binary(string) ->
{:halt, {:ok, string}}
ast ->
maybe_evaluate_ast(ast, caller, acc, evaluate?)
end
end)
end
defp expand_fragments!(fragments, caller) do
Enum.map(fragments, &expand_fragment!(&1, caller))
end
# credo:disable-for-next-line
defp expand_fragment!(ast, caller) do
ast
|> Macro.prewalker()
|> Enum.reduce_while(:error, fn
string, acc when is_binary(string) ->
# We went too far
{:halt, acc}
{:@, _, [{name, _, _}]}, acc ->
case get_module_attribute(caller.module, name) do
%GraphqlQuery.Fragment{} = fragment ->
{:halt, {:ok, fragment}}
%GraphqlQuery.Document{} ->
{:halt, {:error, :document}}
:undefined ->
{:halt, {:error, :module_attribute}}
_ ->
{:cont, acc}
end
expr, acc ->
case Macro.expand(expr, caller) do
{:%{}, [], q} = struct_ast ->
case q[:__struct__] do
GraphqlQuery.Document ->
{:halt, {:error, :document}}
GraphqlQuery.Fragment ->
{fragment, _} = Code.eval_quoted(struct_ast)
{:halt, {:ok, fragment}}
_ ->
{:cont, acc}
end
ast ->
# credo:disable-for-next-line
case evaluate_ast(ast, caller) do
{:ok, %GraphqlQuery.Fragment{} = fragment} ->
{:halt, {:ok, fragment}}
{:ok, %GraphqlQuery.Document{}} ->
{:halt, {:error, :document}}
_ ->
{:cont, acc}
end
end
end)
|> case do
{:ok, fragment} ->
fragment
{:error, error} ->
msg = error_msg_invalid_fragment(ast, error)
IO.warn(msg, warn_location(ast, caller))
nil
:error ->
msg = error_msg_invalid_fragment(ast, nil)
IO.warn(msg, warn_location(ast, caller))
nil
end
end
defp maybe_evaluate_ast(_ast, _caller, acc, false) do
{:cont, acc}
end
defp maybe_evaluate_ast(ast, caller, acc, true) do
case evaluate_ast(ast, caller) do
{:ok, value} when is_binary(value) ->
{:halt, {:ok, value}}
{:ok, %GraphqlQuery.Document{} = query} ->
{:halt, {:ok, to_string(query)}}
{:ok, %GraphqlQuery.Fragment{} = fragment} ->
{:halt, {:ok, to_string(fragment)}}
_ ->
{:cont, acc}
end
end
# Function calls
defp evaluate_ast({{:., _, _}, _, _} = ast, caller) do
ensure_modules_loaded(ast)
{value, _binding} = Code.eval_quoted(ast, [], caller)
{:ok, value}
rescue
_ ->
:error
end
defp evaluate_ast({:@, _, _} = ast, caller) do
{value, _binding} = Code.eval_quoted(ast, [], caller)
{:ok, value}
rescue
_ ->
:error
end
defp evaluate_ast(_ast, _caller), do: :ignore
defp ensure_modules_loaded({:., _meta, [module | _]}) do
ensure_module_loaded!(module)
end
defp ensure_modules_loaded({{:., _, _} = call_ast, _, asts}) do
ensure_modules_loaded(call_ast)
Enum.each(asts, &ensure_module_loaded!/1)
end
defp ensure_modules_loaded({_, _meta, asts}) when is_list(asts) do
Enum.each(asts, &ensure_modules_loaded/1)
end
defp ensure_module_loaded!(nil), do: nil
defp ensure_module_loaded!({:__aliases__, _meta, [module | _] = parts}) when is_atom(module) do
parts |> Module.concat() |> ensure_module_loaded!()
end
defp ensure_module_loaded!(module) when is_atom(module) do
Code.ensure_compiled!(module)
Code.ensure_loaded!(module)
module
end
defp ensure_module_loaded!(other), do: other
defp validate_on_runtime(document, query_opts, warn_location) do
quote do
require Logger
calculated_query = unquote(document)
file_path = unquote(warn_location)[:file]
query = Document.new(calculated_query, unquote(query_opts))
case Validator.validate(query) do
:ok ->
:ok
{:error, errors} ->
Enum.each(errors, fn error ->
error = GraphqlQuery.Parser.format_error(error, unquote(warn_location), :runtime)
Logger.warning(error.message, error.location)
end)
end
query
end
end
defp do_validate(document, warn_location) do
case Validator.validate(document) do
:ok ->
document
{:error, errors} ->
print_warnings(errors, warn_location, "Validation error:")
document
end
end
defp print_warnings(errors, warn_location, prefix) do
Enum.each(errors, fn error ->
error = Parser.format_error(error, warn_location, prefix)
IO.warn(error.message, error.location)
end)
end
defp error_msg_invalid_fragment(ast, :document) do
# We tried to evaluate the query at compile time, but it failed
"""
[GraphqlQuery] Fragment in #{Macro.to_string(ast)} evaluated as %GraphqlQuery.Document{}
In the fragment's definition use the option `type: :fragment`
or the `f` modifier in the sigil `~GQL""f` to define a fragment.
To ignore this warning, use the `ignore: true` option.
"""
end
defp error_msg_invalid_fragment(ast, :module_attribute) do
# We tried to evaluate a @module_attribute at compile time, but it failed
ast_string = Macro.to_string(ast)
"""
[GraphqlQuery] Tried to evaluate the module attribute #{ast_string} at compile time and failed.
This happens when you reference a non existing module attribute or from other module attribute,
that's not possible in Elixir macros.
Move this call to a method, or the module attribute #{ast_string} to another module.
To ignore this warning, use the `ignore: true` option.
"""
end
defp error_msg_invalid_fragment(ast, _) do
# We tried to evaluate the query at compile time, but it failed
"""
[GraphqlQuery] Could not expand to a valid %GraphqlQuery.Fragment{} struct the part #{Macro.to_string(ast)} at compile time.
To validate in runtime, use the `runtime: true` option.
To ignore this warning, use the `ignore: true` option.
"""
end
defp error_msg(ast, true) do
# We tried to evaluate the query at compile time, but it failed
"""
[GraphqlQuery] Could not expand and evaluate the part #{Macro.to_string(ast)} at compile time.
To validate in runtime, use the `runtime: true` option.
To ignore this warning, use the `ignore: true` option.
"""
end
defp error_msg(ast, false) do
# We tried to expand, but not evaluate
"""
[GraphqlQuery] Could not expand the part #{Macro.to_string(ast)} at compile time.
To try to evaluate calls at compile time, use the `evaluate: true` option.
To validate in runtime, use the `runtime: true` option.
To ignore this warning, use the `ignore: true` option.
"""
end
defp get_schema_module(opts, caller) do
case get_option(opts, :schema, nil, caller) do
nil ->
nil
:not_set ->
# If schema is not set, we try to get it from the module attributes
get_module_attribute(caller.module, :__graphql_query__schema, nil)
|> ensure_module_loaded!()
module when is_atom(module) ->
ensure_module_loaded!(module)
{:__aliases__, _meta, _mod_parts} = module_alias ->
ensure_module_loaded!(module_alias)
_ ->
nil
end
end
defp get_option(opts, key, default, caller) do
module_attribute_key = :"__graphql_query__#{key}"
case Keyword.get(opts, key) do
nil ->
get_module_attribute(caller.module, module_attribute_key, default)
value ->
value
end
# case get_in(opts, [Access.key(key)]) do
# nil ->
# get_module_attribute(caller.module, module_attribute_key, default)
# value ->
# value
# end
end
defp validate_options!(options) do
GraphqlQuery.MacroOptions.validate!(Keyword.delete(options, :schema))
end
defp get_module_attribute(module, key) do
if Module.has_attribute?(module, key) do
Module.get_attribute(module, key)
else
:undefined
end
end
defp get_module_attribute(nil, _key, default), do: default
defp get_module_attribute(module, key, default) do
case Module.get_attribute(module, key, default) do
nil -> default
value -> value
end
end
end