Characterizing Support for a Third-party Library: A Study of External Pull Requests for npm packages

Third-party libraries play a key role in building contemporary software applications. Despite this, most libraries are open source that often rely on volunteer (usually unpaid and overworked) contributions for their sustainability. Our motivation is to understand the extent to which third-party libraries are supported by contributions in the form of Pull Requests (PR) from outside the project team (i.e., External PR). Concretely, we analyze 1,076,123 PRs to investigate the External PR prevalence, bots, and the PR characteristics. Our results show that external contributions are prevalent, with packages receiving a high rate of (median of 73.45%) External PR . Furthermore, contributors are also submitting a high proportion of External PR (median of 87.62%). Results indicate a statistical difference in the acceptance of PRs submitted by bots compared to abandoned or open PRs. Furthermore, comparing external and internal PR, we find that Internal PR are more likely to be accepted. Statistically, we find that submitted patches (i.e., commit and code metrics) submitted by Internal PR are higher than patches submitted by External PR. We find that the External PR and Internal PR both have the same content (i.e., introducing new features and fixing bugs). Differently, External PR have more PRs that relate to documentation content, while Internal PR relates to refactoring-related changes