ChangeLog.md

RxRuby Change log

Release 0.1.0

Removed operators and classes

Note that these removals are mostly motivated by reducing the amount of code to write tests for; we may well want to introduce them again later.

• Remove Observable.subscribe_on_next/error/completed as they are problematic in that it is not clear that you can only use one of them.
• Remove ObserveOnObserver and make its superclass ScheduledObsever take its role; they did not have a clean separation of concerns.
• Remove Observer.create; having a specific method for triple-lambda is not worth the confusion; use Observer.configure instead.
• Remove stub ReplaySubject until it can be properly implemented.
• Remove .contains which duplicates .contains?
• Remove .dispose on subscriptions. While the name dispose/disposable might be more distinct, the codebase is dominated by subscribe/unsubscribe/subscription.
• Remove .element_at_or_default, .first_or_default, .last_or_default, .single_or_default operators and equip .element_at, .first, .last, .single with optional default value parameters.
• Remove .min_by and .max_by. These are inspired by Ruby where they add convenience over .min/.max by allowing you to pick the to compare, but unlike Ruby's return lists. They seem to have no equivalent in other modern ReactiveX implementations.
• Remove .pairs which is not correctly implemented; try .buffer_with_count(2).
• Remove .take_last_buffer. Use .take_last(n).to_a instead; this method is no longer in RxJS 5 either.
• Remove .tap as an alias of .do; .tap is a Ruby object builtin and quite useful on Observables in some cases.
• Remove .when, .and operators because of the extensive testing/fixing needed; try .fork_join or .zip instead.

Breaking changes

• .delay_with_selector now accepts a block as selector rather than a lambda.
• .distinct_until_changed now accepts a comparator function, using <=> for default.
• .if no longer takes a scheduler to pass to empty else arguments; if you really need to pass the completion on a separate scheduler you will have to pass your own .empty.
• .min and .max now takes a block that will get two arguments comparator-style and is expected to return -1, 0 or 1 much as <=> (which is the default comparator).
• .timestamp now emits structs rather than hash values to reduce risk of confusion with processed values.
• Drop support for Ruby 1.8.

Bugfixes

• BehaviorSubject now handles on_error, on_completed.
• ConnectableObservable.ref_count counts references properly and unsubscribes on last.
• .any? now applies block with .select rather than .map as .map will always emit, making .any? return true regardless of input.
• .average, .sum generates detailed exceptions on non-numerical input.
• .concat now unsubscribes sources when they are exhausted.
• DefaultScheduler scheduling actions previously did Thread#exit on unsubscribe. However, where the scheduling call (e.g. subscribe_on) occurs in the middle of a chain, we do not actually know that the thread is done when the scheduling subscription unsubscribe method is triggered (e.g. by AutoDetachObserver). This resulted in operations like .merge_all and .merge_concurrent that lack rigid connection between upstream and downstream subscriptions would work fine in synchronous operation, but the stream would mysteriously die when put on DefaultScheduler. Given that Thread.exit on a worker thread with a finite lifecycle is a dubious concept at the best of times, this PR simply removes the composite subscription and passes out a SingleAssignmentSubscription instead.
• .delay now propagates errors immediately.
• .distinct_until_changed now treats nil as an ordinary value.
• .first, .element_at now on_errors rather than raise on "sequence contains no elements".
• .fork_join avoids lambda return which fails on older Ruby.
• .group_join now emits right-hand values on left-hand subjects.
• .group_join right duration exceptions now inform subjects.
• .latest now unsubscribes inner observables.
• .latest now completes only when both outer and inner observable has completed.
• .materialize now emits errors as on_error notifications (rather than on_next notifications)
• .merge now propagates unsubscribes to inner observables.
• .merge_concurrent now propagates unsubscribes to inner observables.
• .multicast subscribes properly to its connectable.
• .none? now .select according to block (rather than block negation; since .any? is fail-fast) and then map-invert the result (like .all?).
• Recursively scheduled items now produce proper subscriptions so that they can be cancelled.
• .rescue_error actually tries left observable (i.e. self) before trying alternate observable.
• .sample now respects nil values.
• .sample propagates recipe exceptions properly.
• .scan operator use next instead of break.
• ScheduledObserver passes error to wrapped observer or it is very likely to "disappear" since we are very likely to be on a thread.
• .sequence_eql? now unsubscribes completed sequences immediately, rather than when the slowest sequence completes.
• .skip_until now completes if upstream completed without emission.
• .skip_while, .skip_while_with_index now continue emitting values after they stop skipping.
• .take_last now emits the correct number of items, rather than always emitting zero values.
• .to_h now uses value selector properly.
• .window_with_time now unsubscribes properly.
• .zip needs to catch errors in result selector.
• New, thread-aware Enumerator implementation used by .concat, .repeat_infinitely and others. RxRuby was using Ruby Enumerator for as an internal short-hand for repeating an Observable a fixed or infinite number of times, for example the .repeat_infinitely operator. The problem with this is that MRI's Enumerator is explicitly thread-averse, as is described in #4 and #10. This affects all places where one part of RxRuby is passing an Enumerator to another part, since the caller cannot know if the receiving observable will be executed across more than one thread.

Improvements:

• Remove instance version of .combine_latest in favour of delegating to class-level .combine_latest.
• Remove internally unused time-math methods from test scheduler.
• .debounce raises argument error on negative numbers.
• Implement time-based .timer.
• CurrentThreadScheduler uses a thread-local queue rather than a class member queue.
• CurrentThreadScheduler is a singleton and can refer to instance members rather than class methods.
• Properly synchronise .delay operator.
• Reimplement .merge_all as .merge_concurrent with infinite concurrency since the latter is properly synchronised.
• Shared scheduler tests no longer delays test execution ~6 seconds; MRI now executes tests in about 2 seconds.
• .multicast defaults to transparent selector so you don't have to give two arguments.
• .publish block is now properly optional.
• .multicast does not accept selector when passed a single subject.
• ConnectableObservable.ref_count now raises when it has already been .connect:ed.
• .skip, .take now throws ArgumentError on negative count.
• reimplement .window_with_time for better readability and properly managed subscriptions. Also fixes the issue that the first window goes first when scheduled on test scheduler, while subsequent windows go after value emission in a particular time slot; an issue since the marble tests don't increment time by 1 for "simultaneous" events.
• subscribing to disposed Subjects yields RuntimeError.
• AsycSubject, BehaviorSubject, Subject delegate subscribing to Observable.subscribe.
• clarify that instance .rescue_error won't accept both alternate observable and block.
• .merge_concurrent validates that max_concurrency is integer.
• .merge_concurrent class version can now be called without scheduler argument as intended.
• .zip should complete as soon as there is no chance of another pair, i.e. when one source has been exhausted and has completed.
• .for block is a "transform", rather than a "result selector".
• ensure argument to .repeat is an integer.
• Rx::Subject allows the normal subscription styles that Observable.subscribe uses - it is an Observable, after all. This PR simply uses the subscribe method from Rx::Observable to normalise the observer setup and instead overrides _subscribe. This also fixes a bug where .to_a assumed that you could use the three-lambda subscription form on itself: https://github.com/bittrance/rxruby/blob/caea16f7e723e8ea6f2241210abae5009b1827c6/lib/rx/operators/aggregates.rb#L523.
• .do no longer requires all three lambdas to be supplied. Despite defaulting its first argument to nil, .do unhelpfully threw nil-class errors on e.g. .do(nil, lambda {|e| ... }, lambda { ... }).