A movie like “In a Relationship” kind of sits there, a bit thin on the entertainment side,  and sends us back to the basics, consulting with the hard and fast rules for a romantic comedy.

Shakespeare invented them, but he never patented that invention, so here they are.

If possible, the lovers must “meet cute.” 

There must be love, love that we root for and love interrupted. The lovers must face obstacles.

Friends must interfere, buck up and/or advise the lovers and if at all possible find love themselves.

The banter is best when it’s biting and sarcastic, the best “obstacle” to our couple.

“In a Relationship” breaks many of these rules, skipping the “meet cute” and never for an instant letting us think writer-director Sam Boyd is the New Bard when it comes to sparkling dialogue.

But it has a lived-in feel, a reality about it that despite the pretty young things of the cast skipping from NYC to LA, makes it feel authentic. This is how real people connect, misconnect, fight and bargain. And that’s almost enough.

Emma Roberts, most recently in “American Horror Story,” is Hallie, a photographer’s assistant five years into her romance with Owen (Michael Angarano, “I’m Dying Up Here”).

“It’s been THREE years,” Owen, a video editor, counters.

A rise in his rent causes her to blurt out “Let’s move in together,” and Owen? He’s in that “No so fast, dear” place. They’ve settled into the foreplay turns into “Let’s watch a movie” stage of the relationship. At least they can agree on the first time “we hung out,” way back in their East (Greenwich) Village youth.

That’s where Owen’s best bud, Matt (Patrick Gibson of Netflix’s “The OA”) first met “Hallie’s hot cousin,” Willa, played by the latest beauty of the clan Hemingway (Dree Hemingway of “While We’re Young”). Willa is on her way to LA.

Matt’s been a bit obsessed, and is all set to renew their acquaintance. But when they all get together at a party, Willa — being unutterably gorgeous and aloof, has no memory of meeting Matt.

Hallie photographs the wrong guy, and Owen shifts from “I miss my FREEDOM” and “maybe we should cool it” to jealous rage in a heartbeat. It all comes to pieces so fast.

Matt? Trusting, needy and just gentlemanly enough to stand out, is REALLY into Willa and willing to push past his tentative nerdy earnestness to take a chance, he goes from “Sorry, I don’t recall” to sharing the coolest Uber in LA to actually having a shot with his dream date.

If you can call it a date.

I like the way Hallie and Owen fight. It’s about something, about differing visions of their future, the fact that she has one and he doesn’t. They know which buttons to push.

“So you just flat out don’t want to live with me?

“I’m not ready to settle down.”

“Stop pretending you care about something just so you can be mad about it!”

Willa loses her aloof cool after a kiss, and even a seduction-in-the-making in Matt’s teenage room in his parents’ house doesn’t blow the mood.

“I’m sorry about my twin bed.”

I know, she says. “I feel like a pedophile.”

“In a Relationship” then settles into dull and contrived — guys over-sharing everything, Owen diving into Mexican junk food and casual hook-ups (failed hook-ups as well), Hallie thrown together with a handsome actor (Jay Ellis) from an HBO sci-fi show she used to watch with Owen, and with others.

Drinking games, skinny dipping, casual flings and molly figure into their disconnected-but-still-connected relationship.

“I’m just happy to be here” needy/clingy Matt starts to realize his romantic dream isn’t all he wishes for. His big romantic gestures (She’s REALLY into the O.J. case, so he books her onto an O.J. murder tour) aren’t getting the reactions he expects.

“She’s like a cat that keeps asking you to pet it. And when you do, she just runs away.”

Random moments of dialogue register; an unhappy woman asking her female friends “Can we look at pictures of sushi on Yelp?” as a coping mechanism, Hallie blurting out “I feel like when you meet someone you know if you’re going to love them!” and Owen shutting down any uncomfortable conversation with “What did we say about fast-talking in the morning?”

To the writer-director’s credit, Willa isn’t painted as a generic cruel beauty. She’s conflicted, drawn to men who aren’t like the puppydog Matt seems to be.

“Am I Felicity?”

“Willa, we’re all Felicity.”

Every character has an arc, which is nice. But they’re all under-developed. Hinting that Hallie has ongoing anxiety issues that border on phobias, suggesting Owen has ambitions beyond editing wedding videos, the shifting dynamic of Willa and Matt’s affair are all interesting enough to pursue or develop without adding to the tight running time.

Too much of what is here feels like filler, not advancing the plot or our understanding of the characters as this cast performs them, not sparkling enough to lift the rom-com beyond “adequate.”

And I feel especially cheated as “In a Relationship” fails to answer that age-old question about Emma Roberts in the movies.

When will she stop taking eye makeup tips from Johnny Depp?

MPAA Rating: unrated

Cast: Emma Roberts, Michael Angarano, Dree Hemingway, Patrick Gibson, Jay Ellis

Credits: Written and directed by Sam Boyd. A Vertical release.

Running time: 1:32