Address omangin's code review.

* This fixes the logic in the `pubs add` command so that an arxiv ID doesn't
  overwrite a DOI.  This also changes the logic so that if an invalid DOI, ISBN,
  or arXiv ID is provided the program will raise an error.

* The code now uses the bibtexparser package to generate the bibtex file for
  arxiv papers.

* A dedicated exception is added for references that can't be found.

pubs/apis.py

@@ -1,9 +1,14 @@
 """Interface for Remote Bibliographic APIs"""
 
 import requests
+import bibtexparser
+from bibtexparser.bibdatabase import BibDatabase
 import feedparser
 from bs4 import BeautifulSoup
-from uis import get_ui
+
+
+class ReferenceNotFoundException(Exception):
+    pass
 
 
 def doi2bibtex(doi):
@@ -38,22 +43,21 @@ def arxiv2bibtex(arxiv_id):
     entry = feed.entries[0]
 
     if 'title' not in entry:
-        ui = get_ui()
-        ui.error('malformed arXiv ID: {}'.format(arxiv_id))
-        bibtex = None
+        raise ReferenceNotFoundException('arXiv ID not found.')
     elif 'arxiv_doi' in entry:
         bibtex = doi2bibtex(entry['arxiv_doi'])
     else:
         # Create a bibentry from the metadata.
-        bibtex = '@misc{{{},\n'.format(arxiv_id)
-        bibtex += 'Author = {'
-        for i, author in enumerate(entry['authors']):
-            bibtex += author['name']
-            if i < len(entry['authors']) - 1:
-                bibtex += ' and '
-        bibtex += '},\n'
-        bibtex += 'Title = {{{}}},\n'.format(entry['title'].strip('\n'))
-        bibtex += 'Year = {{{}}},\n'.format(entry['published_parsed'].tm_year)
-        bibtex += 'Eprint = {{arXiv:{}}},\n'.format(arxiv_id)
-        bibtex += '}'
+        db = BibDatabase()
+        author_str = ' and '.join(
+            [author['name'] for author in entry['authors']])
+        db.entries = [{
+            'ENTRYTYPE': 'misc',
+            'ID': arxiv_id,
+            'author': author_str,
+            'title': entry['title'],
+            'year': str(entry['published_parsed'].tm_year),
+            'Eprint': arxiv_id,
+        }]
+        bibtex = bibtexparser.dumps(db)
     return bibtex

pubs/commands/add_cmd.py

@@ -84,28 +84,33 @@ def command(conf, args):
 
     # get bibtex entry
     if bibfile is None:
-        if args.doi is None and args.isbn is None:
+        if args.doi is None and args.isbn is None and args.arxiv is None:
             bibentry = bibentry_from_editor(conf, ui, rp)
         else:
             bibentry = None
-            if args.doi is not None:
-                bibentry_raw = apis.doi2bibtex(args.doi)
-                bibentry = rp.databroker.verify(bibentry_raw)
-                if bibentry is None:
-                    ui.error('invalid doi {} or unable to retrieve bibfile from it.'.format(args.doi))
-            if args.isbn is not None:
-                bibentry_raw = apis.isbn2bibtex(args.isbn)
-                bibentry = rp.databroker.verify(bibentry_raw)
-                if bibentry is None:
-                    ui.error('invalid isbn {} or unable to retrieve bibfile from it.'.format(args.isbn))
-                # TODO distinguish between cases, offer to open the error page in a webbrowser.
-                # TODO offer to confirm/change citekey
-            if args.arxiv is not None:
-                bibentry_raw = apis.arxiv2bibtex(args.arxiv)
-                bibentry = rp.databroker.verify(bibentry_raw)
-                if bibentry is None:
-                    ui.error('invalid arxiv id {} or unable to retrieve bibfile from it.'.format(args.arxiv_id))
-            if bibentry is None:
+            try:
+                if args.doi is not None:
+                    bibentry_raw = apis.doi2bibtex(args.doi)
+                    bibentry = rp.databroker.verify(bibentry_raw)
+                    if bibentry is None:
+                        raise apis.ReferenceNotFoundException(
+                            'invalid doi {} or unable to retrieve bibfile from it.'.format(args.doi))
+                elif args.isbn is not None:
+                    bibentry_raw = apis.isbn2bibtex(args.isbn)
+                    bibentry = rp.databroker.verify(bibentry_raw)
+                    if bibentry is None:
+                        raise apis.ReferenceNotFoundException(
+                            'invalid isbn {} or unable to retrieve bibfile from it.'.format(args.isbn))
+                    # TODO distinguish between cases, offer to open the error page in a webbrowser.
+                    # TODO offer to confirm/change citekey
+                elif args.arxiv is not None:
+                    bibentry_raw = apis.arxiv2bibtex(args.arxiv)
+                    bibentry = rp.databroker.verify(bibentry_raw)
+                    if bibentry is None:
+                        raise apis.ReferenceNotFoundException(
+                            'invalid arxiv id {} or unable to retrieve bibfile from it.'.format(args.arxiv_id))
+            except apis.ReferenceNotFoundException as e:
+                ui.error(e.message)
                 ui.exit(1)
     else:
         bibentry_raw = content.get_content(bibfile, ui=ui)