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docstrings that can be single line to be formatted on a single line #3107

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docstrings that can be single line to be formatted on a single line #3107

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4efce4f
First try
kevin-paulson-mindbridge-ai Apr 27, 2026
e0b2779
format_docstring the way I want it
kevin-paulson-mindbridge-ai Apr 28, 2026
7ffd3b4
Ready for testing?
kevin-paulson-mindbridge-ai Apr 28, 2026
caa1f49
fix logic error
kevin-paulson-mindbridge-ai Apr 28, 2026
d150443
If single line and ends with " add a space so there isn't 4 " in a row
kevin-paulson-mindbridge-ai Apr 28, 2026
650aeef
Update test outputs
kevin-paulson-mindbridge-ai Apr 28, 2026
5a0ea26
Minor changes after initial review
kevin-paulson-mindbridge-ai Apr 28, 2026
6398d94
inline_field_docstring to use same logic
kevin-paulson-mindbridge-ai Apr 28, 2026
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48 changes: 43 additions & 5 deletions src/datamodel_code_generator/model/base.py
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Expand Up @@ -7,6 +7,7 @@
from __future__ import annotations

import re
import textwrap
from abc import ABC, abstractmethod
from collections import defaultdict
from copy import deepcopy
Expand Down Expand Up @@ -66,6 +67,40 @@ def escape_docstring(value: str | None) -> str | None:
return value.replace("\\", "\\\\").replace('"""', '\\"\\"\\"')


def format_docstring(value: str | None, indent_spaces: int = 0) -> str:
"""Format *value* as a docstring as per PEP 257.

PEP 257 recommends that docstrings that can fit on one line should be formatted on a
single line, for consistency and readability. Leading and trailing whitespace will
be removed, and if after this the value is falsy, an empty string is returned. It is
assumed that the opening triple-quotes are indented appropriately in the template.
If it's a multi-line docstring, each line including the closing triple-quotes will
be indented as per indent_spaces.

Args:
value: docstring text
indent_spaces: Spaces to indent for all lines after the opening triple-quotes

Returns:
Empty string when `value` is falsy; otherwise the docstring block.
"""
value = (value or "").strip()

if not value:
return ""

escaped = escape_docstring(value)

if len(value.splitlines()) == 1:
if escaped.endswith('"'):
escaped = f"{escaped} "

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return f'"""{escaped}"""'

indent_text = textwrap.indent(f'{escaped}\n"""', max(indent_spaces, 0) * " ")
return f'"""\n{indent_text}'


ALL_MODEL: str = "#all#"
GENERIC_BASE_CLASS_PATH: str = "#/__datamodel_code_generator__/generic_base_class__"
GENERIC_BASE_CLASS_NAME: str = "__generic_base_class__"
Expand Down Expand Up @@ -354,9 +389,10 @@ def inline_field_docstring(self) -> str | None:
"""Get the inline docstring for this field if single-line."""
if self.use_inline_field_description:
description = self.extras.get("description", None)
if description is not None and "\n" not in description:
escaped = escape_docstring(description)
return f'"""{escaped}"""'
docstring = format_docstring(description, 0)
if docstring:
return docstring

return None

@property
Expand Down Expand Up @@ -452,7 +488,8 @@ def _get_environment(template_subdir: Path, custom_template_dir: Path | None) ->
loader=loader,
autoescape=select_autoescape(["html", "xml"]),
)
env.filters["escape_docstring"] = escape_docstring
env.filters["escape_docstring"] = escape_docstring # For old custom templates
env.filters["format_docstring"] = format_docstring
return env


Expand Down Expand Up @@ -485,7 +522,8 @@ def _get_environment_with_absolute_path(absolute_template_dir: Path, builtin_sub
loader=ChoiceLoader(loaders),
autoescape=select_autoescape(["html", "xml"]),
)
env.filters["escape_docstring"] = escape_docstring
env.filters["escape_docstring"] = escape_docstring # For old custom templates
env.filters["format_docstring"] = format_docstring
return env


Expand Down
8 changes: 2 additions & 6 deletions src/datamodel_code_generator/model/template/Enum.jinja2
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Expand Up @@ -3,16 +3,12 @@
{% endfor -%}
class {{ class_name }}({{ base_class }}):
{%- if description %}
"""
{{ description | escape_docstring | indent(4) }}
"""
{{ description | format_docstring(4) }}
{%- endif %}
{%- for field in fields %}
{{ field.name }} = {{ field.default }}
{%- if field.docstring %}
"""
{{ field.docstring | escape_docstring | indent(4) }}
"""
{{ field.docstring | format_docstring(4) }}
{%- if field.use_inline_field_description and not loop.last %}

{% endif %}
Expand Down
4 changes: 1 addition & 3 deletions src/datamodel_code_generator/model/template/ScalarTypeAliasAnnotation.jinja2
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@@ -1,6 +1,4 @@
{{ class_name }}: TypeAlias = {{ py_type }}
{%- if description %}
"""
{{ description }}
"""
{{ description | format_docstring(0) }}
{%- endif %}
4 changes: 1 addition & 3 deletions src/datamodel_code_generator/model/template/ScalarTypeAliasType.jinja2
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@@ -1,6 +1,4 @@
{{ class_name }} = TypeAliasType("{{ class_name }}", {{ py_type }})
{%- if description %}
"""
{{ description }}
"""
{{ description | format_docstring(0) }}
{%- endif %}
6 changes: 2 additions & 4 deletions src/datamodel_code_generator/model/template/ScalarTypeStatement.jinja2
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@@ -1,6 +1,4 @@
type {{ class_name }} = {{ py_type }}
{%- if description %}
"""
{{ description }}
"""
{%- endif %}
{{ description | format_docstring(0) }}
{%- endif %}
12 changes: 3 additions & 9 deletions src/datamodel_code_generator/model/template/TypeAliasAnnotation.jinja2
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Expand Up @@ -11,19 +11,13 @@ Annotated[{{ _field.type_hint }}, {{ _field.field }}]
{%- if fields %}
{{ class_name }}: TypeAlias = {{ get_type_annotation(fields[0]) }}{% if comment is defined %} # {{ comment }}{% endif %}
{%- if description %}
"""
{{ description | escape_docstring | indent(0) }}
"""
{{ description | format_docstring(0) }}
{%- elif fields[0].docstring %}
"""
{{ fields[0].docstring | escape_docstring | indent(0) }}
"""
{{ fields[0].docstring | format_docstring(0) }}
{%- endif %}
{%- else %}
{{ class_name }}: TypeAlias = {{ base_class }}{% if comment is defined %} # {{ comment }}{% endif %}
{%- if description %}
"""
{{ description | escape_docstring | indent(0) }}
"""
{{ description | format_docstring(0) }}
{%- endif %}
{%- endif %}
12 changes: 3 additions & 9 deletions src/datamodel_code_generator/model/template/TypeAliasType.jinja2
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Expand Up @@ -11,19 +11,13 @@ Annotated[{{ _field.type_hint }}, {{ _field.field }}]
{%- if fields %}
{{ class_name }} = TypeAliasType("{{ class_name }}", {{ get_type_annotation(fields[0]) }}){% if comment is defined %} # {{ comment }}{% endif %}
{%- if description %}
"""
{{ description | escape_docstring | indent(0) }}
"""
{{ description | format_docstring(0) }}
{%- elif fields[0].docstring %}
"""
{{ fields[0].docstring | escape_docstring | indent(0) }}
"""
{{ fields[0].docstring | format_docstring(0) }}
{%- endif %}
{%- else %}
{{ class_name }} = TypeAliasType("{{ class_name }}", {{ base_class }}){% if comment is defined %} # {{ comment }}{% endif %}
{%- if description %}
"""
{{ description | escape_docstring | indent(0) }}
"""
{{ description | format_docstring(0) }}
{%- endif %}
{%- endif %}
14 changes: 4 additions & 10 deletions src/datamodel_code_generator/model/template/TypeStatement.jinja2
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Expand Up @@ -11,19 +11,13 @@ Annotated[{{ _field.type_hint }}, {{ _field.field }}]
{%- if fields %}
type {{ class_name }} = {{ get_type_annotation(fields[0]) }}{% if comment is defined %} # {{ comment }}{% endif %}
{%- if description %}
"""
{{ description | escape_docstring | indent(0) }}
"""
{{ description | format_docstring(0) }}
{%- elif fields[0].docstring %}
"""
{{ fields[0].docstring | escape_docstring | indent(0) }}
"""
{{ fields[0].docstring | format_docstring(0) }}
{%- endif %}
{%- else %}
type {{ class_name }} = {{ base_class }}{% if comment is defined %} # {{ comment }}{% endif %}
{%- if description %}
"""
{{ description | escape_docstring | indent(0) }}
"""
{{ description | format_docstring(0) }}
{%- endif %}
{%- endif %}
{%- endif %}
8 changes: 2 additions & 6 deletions src/datamodel_code_generator/model/template/TypedDictClass.jinja2
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@@ -1,18 +1,14 @@
class {{ class_name }}({{ base_class }}):
{%- if description %}
"""
{{ description | escape_docstring | indent(4) }}
"""
{{ description | format_docstring(4) }}
{%- endif %}
{%- if not fields and not description %}
pass
{%- endif %}
{%- for field in fields %}
{{ field.name }}: {{ field.type_hint }}
{%- if field.docstring %}
"""
{{ field.docstring | escape_docstring | indent(4) }}
"""
{{ field.docstring | format_docstring(4) }}
{%- if field.use_inline_field_description and not loop.last %}

{% endif %}
Expand Down
8 changes: 2 additions & 6 deletions src/datamodel_code_generator/model/template/TypedDictFunction.jinja2
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@@ -1,15 +1,11 @@
{%- if description %}
"""
{{ description | escape_docstring | indent(4) }}
"""
{{ description | format_docstring(4) }}
{%- endif %}
{{ class_name }} = TypedDict('{{ class_name }}', {
{%- for field in all_fields %}
'{{ field.key }}': {{ field.type_hint }},
{%- if field.docstring %}
"""
{{ field.docstring | escape_docstring | indent(4) }}
"""
{{ field.docstring | format_docstring(4) }}
{%- if field.use_inline_field_description and not loop.last %}

{% endif %}
Expand Down
8 changes: 2 additions & 6 deletions src/datamodel_code_generator/model/template/dataclass.jinja2
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Expand Up @@ -18,9 +18,7 @@ class {{ class_name }}({{ base_class }}):
class {{ class_name }}:
{%- endif %}
{%- if description %}
"""
{{ description | escape_docstring | indent(4) }}
"""
{{ description | format_docstring(4) }}
{%- endif %}
{%- if not fields and not description %}
pass
Expand All @@ -35,9 +33,7 @@ class {{ class_name }}:
{%- endif -%}
{%- endif %}
{%- if field.docstring %}
"""
{{ field.docstring | escape_docstring | indent(4) }}
"""
{{ field.docstring | format_docstring(4) }}
{%- if field.use_inline_field_description and not loop.last %}

{% endif %}
Expand Down
8 changes: 2 additions & 6 deletions src/datamodel_code_generator/model/template/msgspec.jinja2
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Expand Up @@ -9,9 +9,7 @@ class {{ class_name }}({{ base_class }}{%- for key, value in (base_class_kwargs|
class {{ class_name }}:
{%- endif %}
{%- if description %}
"""
{{ description | escape_docstring | indent(4) }}
"""
{{ description | format_docstring(4) }}
{%- endif %}
{%- set ns = namespace(has_rendered_field=false) -%}
{%- for field in fields -%}
Expand All @@ -37,9 +35,7 @@ class {{ class_name }}:


{%- if not field.extras.get('is_classvar') and field.docstring %}
"""
{{ field.docstring | escape_docstring | indent(4) }}
"""
{{ field.docstring | format_docstring(4) }}
{%- if field.use_inline_field_description and not loop.last %}

{% endif %}
Expand Down
8 changes: 2 additions & 6 deletions src/datamodel_code_generator/model/template/pydantic_v2/BaseModel.jinja2
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Expand Up @@ -3,9 +3,7 @@
{% endfor -%}
class {{ class_name }}({{ base_class }}):{% if comment is defined %} # {{ comment }}{% endif %}
{%- if description %}
"""
{{ description | escape_docstring | indent(4) }}
"""
{{ description | format_docstring(4) }}
{%- endif %}
{%- if not fields and not description and not config and not class_body_lines %}
pass
Expand All @@ -32,9 +30,7 @@ class {{ class_name }}({{ base_class }}):{% if comment is defined %} # {{ comme
{%- endif -%}
{%- endif %}
{%- if field.docstring %}
"""
{{ field.docstring | escape_docstring | indent(4) }}
"""
{{ field.docstring | format_docstring(4) }}
{%- if field.use_inline_field_description and not loop.last %}

{% endif %}
Expand Down
8 changes: 2 additions & 6 deletions src/datamodel_code_generator/model/template/pydantic_v2/RootModel.jinja2
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Expand Up @@ -18,9 +18,7 @@
{%- set use_base_type = config and config.regex_engine -%}
class {{ class_name }}({{ base_class }}{%- if fields -%}[{{get_type_hint(fields, use_base_type)}}]{%- endif -%}):{% if comment is defined %} # {{ comment }}{% endif %}
{%- if description %}
"""
{{ description | escape_docstring | indent(4) }}
"""
{{ description | format_docstring(4) }}
{%- endif %}
{%- if config %}
{%- filter indent(4) %}
Expand All @@ -47,9 +45,7 @@ class {{ class_name }}({{ base_class }}{%- if fields -%}[{{get_type_hint(fields,
{%- endif -%}
{%- endif %}
{%- if field.docstring %}
"""
{{ field.docstring | escape_docstring | indent(4) }}
"""
{{ field.docstring | format_docstring(4) }}
{%- elif field.inline_field_docstring %}
{{ field.inline_field_docstring }}

Expand Down
8 changes: 2 additions & 6 deletions src/datamodel_code_generator/model/template/pydantic_v2/RootModelTypeAlias.jinja2
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Expand Up @@ -12,11 +12,7 @@
{%- set use_base_type = config and config.regex_engine -%}
{{ class_name }} = RootModel[{{get_type_hint(fields, use_base_type)}}]{% if comment is defined %} # {{ comment }}{% endif %}
{%- if description %}
"""
{{ description }}
"""
{{ description | format_docstring(0) }}
{%- elif fields and fields[0].docstring %}
"""
{{ fields[0].docstring }}
"""
{{ fields[0].docstring | format_docstring(0) }}
{%- endif %}
8 changes: 2 additions & 6 deletions src/datamodel_code_generator/model/template/pydantic_v2/dataclass.jinja2
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Expand Up @@ -25,9 +25,7 @@ class {{ class_name }}({{ base_class }}):
class {{ class_name }}:
{%- endif %}
{%- if description %}
"""
{{ description | escape_docstring | indent(4) }}
"""
{{ description | format_docstring(4) }}
{%- endif %}
{%- if not fields and not description %}
pass
Expand All @@ -46,9 +44,7 @@ class {{ class_name }}:
{%- endif -%}
{%- endif %}
{%- if field.docstring %}
"""
{{ field.docstring | escape_docstring | indent(4) }}
"""
{{ field.docstring | format_docstring(4) }}
{%- if field.use_inline_field_description and not loop.last %}

{% endif %}
Expand Down
12 changes: 3 additions & 9 deletions tests/data/expected/main/graphql/additional_imports.py
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Expand Up @@ -12,27 +12,21 @@
from typing_extensions import TypeAliasType

Boolean = TypeAliasType("Boolean", bool)
"""
The `Boolean` scalar type represents `true` or `false`.
"""
"""The `Boolean` scalar type represents `true` or `false`."""


Date = TypeAliasType("Date", date)


DateTime = TypeAliasType("DateTime", datetime)
"""
DateTime (ISO8601, example: 2020-01-01T10:11:12+00:00)
"""
"""DateTime (ISO8601, example: 2020-01-01T10:11:12+00:00)"""


MyCustomClass = TypeAliasType("MyCustomClass", MyCustomPythonClass)


String = TypeAliasType("String", str)
"""
The `String` scalar type represents textual data, represented as UTF-8 character sequences. The String type is most often used by GraphQL to represent free-form human-readable text.
"""
"""The `String` scalar type represents textual data, represented as UTF-8 character sequences. The String type is most often used by GraphQL to represent free-form human-readable text."""


class A(BaseModel):
Expand Down
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