function updateFnode()

in src/js/other-websites/fathom.js [2285:2315]
23 lines of code
8 McCabe index (conditional complexity)

                function updateFnode(leftResult) {
                    const leftType = self.lhs.guaranteedType();
                    // Get a fnode and a RHS transformer, whether a plain fnode is
                    // returned or a {fnode, rhsTransformer} pair:
                    const {fnode: leftFnode = leftResult, rhsTransformer = identity} = leftResult;
                    // Grab the fact from the RHS, and run the LHS's optional
                    // transformer over it to pick up anything special it wants to
                    // do:
                    const fact = rhsTransformer(self.rhs.fact(leftFnode, leftType));
                    self.lhs.checkFact(fact);
                    const rightFnode = ruleset.fnodeForElement(fact.element || leftFnode.element);
                    // If the RHS doesn't specify a type, default to the
                    // type of the LHS, if any:
                    const rightType = fact.type || self.lhs.guaranteedType();
                    if (fact.score !== undefined) {
                        if (rightType !== undefined) {
                            rightFnode.addScoreFor(rightType, fact.score, self.name);
                        } else {
                            throw new Error(`The right-hand side of a rule specified a score (${fact.score}) with neither an explicit type nor one we could infer from the left-hand side.`);
                        }
                    }
                    if (fact.type !== undefined || fact.note !== undefined) {
                        // There's a reason to call setNoteFor.
                        if (rightType === undefined) {
                            throw new Error(`The right-hand side of a rule specified a note (${fact.note}) with neither an explicit type nor one we could infer from the left-hand side. Notes are per-type, per-node, so that's a problem.`);
                        } else {
                            rightFnode.setNoteFor(rightType, fact.note);
                        }
                    }
                    returnedFnodes.add(rightFnode);
                },