Are you sure you are happy?

Context: The study of emotions, especially those that promote an apparent increase in performance at the workplace, has received considerable attention since the early days of the industrial revolution. In the much newer area of software engineering, these studies include affections, emotions, motivation and happiness, among other feelings. However, there are still many fallacies, misconceptions and ambiguous definitions, which prevent a useful assessment of these issues. Objective: the aim of this study is to summarize the existing definitions of happiness as well as the appropriate metrics to assess its level on software engineers. Method: a systematic search in several online electronic data sources, complemented with snowballing techniques, to identify and select published literature, supporting happiness research in software engineering. We reported the findings as an annotated literature review. Results: The search strategies retrieved 619 publications, from which we selected 18 primary works. These works were grouped into three categories, according to their focus: a) definition of happiness, b) metrics to measure happiness, and c) general purpose articles. The review provides a description of 8 articles, 4 in the first category and 4 in the second. Conclusions: Research on "happiness at work" has its own issues and challenges, as reported in the articles in this review. Our work can contribute by shedding light on these challenges, highlighting the precise definitions and showing the appropriate metrics to assess them. There is still too much to do since research shows a high degree of divergence in the results.