Vowel length in Maltese seems to be one of those tricky things. The combination of pronominal suffixes with verbs ending in ‘a’ is a good example.
Direct Object suffixes
Think of the single verb form for “we saw you”: rajniek. Or should that be rajnik? Based on how it sounds as a native speaker, the latter shorter-vowel version seems more likely.
The Maltese corpus is not much help in deciding this. Just look at these frequency counts for tokens ending in jniek and jnik:
In total, jniek occurs 17 times and jnik occurs 18 times. Note also the even split of the words which appear in both lists: tajniek (4) vs. tajnik (3), and rajniek (2) vs. rajnik (2).
But it turns out there is an explicit rule for this. According to “Grammatika Maltija” pg 166, whenever a verb ending in ‘a’ is going to have a pronominal suffix attached to it, the joining vowel becomes an ‘ie’. So tajna + ek = tajniek, even though when you say it it sounds a lot more like tajnik. The results from the corpus seem to confirm that I’m not the only one confused by this, although admittedly the numbers are probably too low to be statistically significant. While counter-intuitive, this rule seems pretty established, so we just accept it.
Indirect Object suffixes
What about indirect pronominal suffixes? Think of “we sang for your”, kantajnielek. Or is that kantajnilek? Again, the latter sounds like a more accurately transcription of the spoken form. The corpus reports 11 occurances of tokens ending in jnielek, and 10 for jnilek. Another even non-statistically-significant split. “Maltese” by Borg and Azzopardi-Alexander claims the former is correct, with an ‘ie’.
Direct and Indirect Object suffixes
And what happens when you have both a direct and indirect pronominal suffixes? The information is much more polarised. Using the rule above, as in “Maltese”, the ‘ie’ remains. So you have the forms kantajniehulek and ftaħniehulek.
But the corpus contains exactly zero tokens which end with iehulek, and a whopping 92 which finish with ihulek. In this case the two sources directly contradict each other. Some personal communication on the Kelmet il-Malti Facebook group confirms that the above rule no longer applies, and the more natural principle of vowel length comes into play again. So kantajnihulek and ftaħnihulek are the correct forms, and the book is wrong.