🚸 Raise warning if parser is used multiple times (#312)

Author: echomehran

.gitignore

@@ -39,3 +39,6 @@ nosetests.xml
 
 # Vim.
 *.swp
+
+# Vscode
+.vscode

bibtexparser/bparser.py

@@ -8,6 +8,7 @@
 
 import io
 import logging
+import warnings
 
 from bibtexparser.bibdatabase import (BibDatabase, BibDataString, as_text,
                                       BibDataStringExpression, STANDARD_TYPES)
@@ -82,6 +83,12 @@ def __init__(self, data=None,
         :return: parser
         :rtype: `BibTexParser`
         """
+
+        self._parse_call_count = 0
+        #: Parsers can be called multiple times, merging databases, but raising a warning.
+        #      Set this to `True` to disable the warning. Default: `False`
+        self.expect_multiple_parse = False
+
         self.bib_database = BibDatabase()
 
         #: Load common strings such as months abbreviation
@@ -142,6 +149,14 @@ def parse(self, bibtex_str, partial=False):
         :return: bibliographic database
         :rtype: BibDatabase
         """
+
+        self._parse_call_count += 1
+        if self._parse_call_count == 2 and not self.expect_multiple_parse:
+            warnings.warn("The parser has been called more than once. "
+                          "Subsequent parse calls lead to a combined BibTeX library. \n"
+                          "To avoid the warning, set property `parser.expect_multiple_parse` to `True`.",
+                          category=UserWarning, stacklevel=2)
+
         bibtex_file_obj = self._bibtex_file_obj(bibtex_str)
         try:
             self._expr.parseFile(bibtex_file_obj)

bibtexparser/tests/data/article_comma_normal_multiple.bib

@@ -0,0 +1,42 @@
+@article{FuMetalhalideperovskite2019,
+    author = {Yongping Fu and Haiming Zhu and Jie Chen and Matthew P. Hautzinger and X.-Y. Zhu and Song Jin},
+    doi = {10.1038/s41578-019-0080-9},
+    journal = {Nature Reviews Materials},
+    month = {feb},
+    number = {3},
+    pages = {169-188},
+    publisher = {Springer Science and Business Media {LLC}},
+    title = {Metal halide perovskite nanostructures for optoelectronic applications and the study of physical properties},
+    url = {https://www.nature.com/articles/s41578-019-0080-9},
+    volume = {4},
+    year = {2019}
+}
+
+@article{SunEnablingSiliconSolar2014,
+    author = {Ke Sun and Shaohua Shen and Yongqi Liang and Paul E. Burrows and Samuel S. Mao and Deli Wang},
+    doi = {10.1021/cr300459q},
+    journal = {Chemical Reviews},
+    month = {aug},
+    number = {17},
+    pages = {8662-8719},
+    publisher = {American Chemical Society ({ACS})},
+    title = {Enabling Silicon for Solar-Fuel Production},
+    url = {http://pubs.acs.org/doi/10.1021/cr300459q},
+    volume = {114},
+    year = {2014}
+}
+
+@article{LiuPhotocatalytichydrogenproduction2016,
+    author = {Maochang Liu and Yubin Chen and Jinzhan Su and Jinwen Shi and Xixi Wang and Liejin Guo},
+    doi = {10.1038/nenergy.2016.151},
+    impactfactor = {54.000},
+    journal = {Nature Energy},
+    month = {sep},
+    number = {11},
+    pages = {16151},
+    publisher = {Springer Science and Business Media {LLC}},
+    title = {Photocatalytic hydrogen production using twinned nanocrystals and an unanchored {NiSx} co-catalyst},
+    url = {http://www.nature.com/articles/nenergy2016151},
+    volume = {1},
+    year = {2016}
+}

bibtexparser/tests/data/article_comma_normal_single.bib

@@ -0,0 +1,13 @@
+@article{FuMetalhalideperovskite2019,
+    author = {Yongping Fu and Haiming Zhu and Jie Chen and Matthew P. Hautzinger and X.-Y. Zhu and Song Jin},
+    doi = {10.1038/s41578-019-0080-9},
+    journal = {Nature Reviews Materials},
+    month = {feb},
+    number = {3},
+    pages = {169-188},
+    publisher = {Springer Science and Business Media {LLC}},
+    title = {Metal halide perovskite nanostructures for optoelectronic applications and the study of physical properties},
+    url = {https://www.nature.com/articles/s41578-019-0080-9},
+    volume = {4},
+    year = {2019}
+}

bibtexparser/tests/test_bparser.py

@@ -6,7 +6,9 @@
 import os
 import unittest
 import codecs
+import warnings
 
+import bibtexparser
 from bibtexparser.bparser import BibTexParser
 from bibtexparser.bibdatabase import (COMMON_STRINGS, BibDataStringExpression)
 from bibtexparser.customization import *
@@ -650,6 +652,60 @@ def test_no_citekey_parsed_as_comment(self):
         self.assertEqual(bib.strings, {})
         self.assertEqual(bib.comments, ['@BOOK{, title = "bla"}'])
 
+    def test_parsing_just_once_not_raising_warnings_with_default_settings(self):
+        parser = BibTexParser()
+
+        with open('bibtexparser/tests/data/article_comma_normal_single.bib',
+                  'r', encoding='utf-8') as bibfile:
+            with warnings.catch_warnings(record=True) as warning:
+                warnings.simplefilter("always")
+                bibtexparser.load(bibfile, parser)
+                assert len(warning) == 0
+
+    def test_parsing_twice_raise_warnings_with_default_settings(self):
+        parser = BibTexParser()
+
+        with open('bibtexparser/tests/data/article_comma_normal_single.bib',
+                  'r', encoding='utf-8') as bibfile_first, \
+            open('bibtexparser/tests/data/article_comma_normal_multiple.bib', 'r', encoding='utf-8') \
+                as bibfile_second:
+            with warnings.catch_warnings(record=True) as warning:
+                warnings.simplefilter("always")
+                bibtexparser.load(bibfile_first, parser)
+                bibtexparser.load(bibfile_second, parser)
+                assert len(warning) != 0
+
+    def test_parsing_three_times_raise_warnings_only_once_with_default_settings(self):
+        parser = BibTexParser()
+
+        with open('bibtexparser/tests/data/article_comma_normal_single.bib',
+                  'r', encoding='utf-8') as bibfile_first, \
+            open('bibtexparser/tests/data/article_comma_normal_multiple.bib', 'r', encoding='utf-8') \
+                as bibfile_second, \
+                open('bibtexparser/tests/data/article.bib', 'r', encoding='utf-8') as bibfile_third:
+            with warnings.catch_warnings(record=True) as warning:
+                warnings.simplefilter("always")
+                bibtexparser.load(bibfile_first, parser)
+                bibtexparser.load(bibfile_second, parser)
+                bibtexparser.load(bibfile_third, parser)
+                assert len(warning) == 1
+
+    def test_parsing_three_times_not_raising_a_warning_if_expect_multiple_parse_is_true(self):
+        parser = BibTexParser()
+        parser.expect_multiple_parse = True
+
+        with open('bibtexparser/tests/data/article_comma_normal_single.bib',
+                  'r', encoding='utf-8') as bibfile_first, \
+            open('bibtexparser/tests/data/article_comma_normal_multiple.bib', 'r', encoding='utf-8') \
+                as bibfile_second, \
+                open('bibtexparser/tests/data/article.bib', 'r', encoding='utf-8') as bibfile_third:
+            with warnings.catch_warnings(record=True) as warning:
+                warnings.simplefilter("always")
+                bibtexparser.load(bibfile_first, parser)
+                bibtexparser.load(bibfile_second, parser)
+                bibtexparser.load(bibfile_third, parser)
+                assert len(warning) == 0
+
 
 if __name__ == '__main__':
     unittest.main()