115 lines
4.7 KiB
Python
115 lines
4.7 KiB
Python
import json
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import sys
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from pypdf import PdfReader, PdfWriter
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from extract_form_field_info import get_field_info
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# Fills fillable form fields in a PDF. See forms.md.
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def fill_pdf_fields(input_pdf_path: str, fields_json_path: str, output_pdf_path: str):
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with open(fields_json_path) as f:
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fields = json.load(f)
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# Group by page number.
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fields_by_page = {}
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for field in fields:
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if "value" in field:
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field_id = field["field_id"]
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page = field["page"]
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if page not in fields_by_page:
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fields_by_page[page] = {}
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fields_by_page[page][field_id] = field["value"]
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reader = PdfReader(input_pdf_path)
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has_error = False
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field_info = get_field_info(reader)
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fields_by_ids = {f["field_id"]: f for f in field_info}
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for field in fields:
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existing_field = fields_by_ids.get(field["field_id"])
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if not existing_field:
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has_error = True
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print(f"ERROR: `{field['field_id']}` is not a valid field ID")
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elif field["page"] != existing_field["page"]:
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has_error = True
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print(f"ERROR: Incorrect page number for `{field['field_id']}` (got {field['page']}, expected {existing_field['page']})")
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else:
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if "value" in field:
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err = validation_error_for_field_value(existing_field, field["value"])
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if err:
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print(err)
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has_error = True
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if has_error:
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sys.exit(1)
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writer = PdfWriter(clone_from=reader)
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for page, field_values in fields_by_page.items():
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writer.update_page_form_field_values(writer.pages[page - 1], field_values, auto_regenerate=False)
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# This seems to be necessary for many PDF viewers to format the form values correctly.
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# It may cause the viewer to show a "save changes" dialog even if the user doesn't make any changes.
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writer.set_need_appearances_writer(True)
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with open(output_pdf_path, "wb") as f:
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writer.write(f)
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def validation_error_for_field_value(field_info, field_value):
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field_type = field_info["type"]
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field_id = field_info["field_id"]
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if field_type == "checkbox":
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checked_val = field_info["checked_value"]
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unchecked_val = field_info["unchecked_value"]
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if field_value != checked_val and field_value != unchecked_val:
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return f'ERROR: Invalid value "{field_value}" for checkbox field "{field_id}". The checked value is "{checked_val}" and the unchecked value is "{unchecked_val}"'
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elif field_type == "radio_group":
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option_values = [opt["value"] for opt in field_info["radio_options"]]
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if field_value not in option_values:
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return f'ERROR: Invalid value "{field_value}" for radio group field "{field_id}". Valid values are: {option_values}'
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elif field_type == "choice":
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choice_values = [opt["value"] for opt in field_info["choice_options"]]
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if field_value not in choice_values:
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return f'ERROR: Invalid value "{field_value}" for choice field "{field_id}". Valid values are: {choice_values}'
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return None
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# pypdf (at least version 5.7.0) has a bug when setting the value for a selection list field.
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# In _writer.py around line 966:
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#
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# if field.get(FA.FT, "/Tx") == "/Ch" and field_flags & FA.FfBits.Combo == 0:
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# txt = "\n".join(annotation.get_inherited(FA.Opt, []))
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#
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# The problem is that for selection lists, `get_inherited` returns a list of two-element lists like
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# [["value1", "Text 1"], ["value2", "Text 2"], ...]
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# This causes `join` to throw a TypeError because it expects an iterable of strings.
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# The horrible workaround is to patch `get_inherited` to return a list of the value strings.
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# We call the original method and adjust the return value only if the argument to `get_inherited`
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# is `FA.Opt` and if the return value is a list of two-element lists.
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def monkeypatch_pydpf_method():
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from pypdf.generic import DictionaryObject
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from pypdf.constants import FieldDictionaryAttributes
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original_get_inherited = DictionaryObject.get_inherited
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def patched_get_inherited(self, key: str, default = None):
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result = original_get_inherited(self, key, default)
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if key == FieldDictionaryAttributes.Opt:
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if isinstance(result, list) and all(isinstance(v, list) and len(v) == 2 for v in result):
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result = [r[0] for r in result]
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return result
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DictionaryObject.get_inherited = patched_get_inherited
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if __name__ == "__main__":
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if len(sys.argv) != 4:
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print("Usage: fill_fillable_fields.py [input pdf] [field_values.json] [output pdf]")
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sys.exit(1)
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monkeypatch_pydpf_method()
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input_pdf = sys.argv[1]
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fields_json = sys.argv[2]
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output_pdf = sys.argv[3]
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fill_pdf_fields(input_pdf, fields_json, output_pdf)
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