zarr-python
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Comparison · DevOps
promises vs xml2
A side-by-side editorial comparison of promises and xml2 — release velocity, themes, recent moves, and the top alternatives to consider.
Shared themes:performance
promises vs xml2: at a glance
What is promises?
promises drops R6 for plain environments and wires async work into OpenTelemetry
promises supplies the async primitives behind Shiny and plumber. After years of small domain and future() fixes, the last two releases changed both what a promise costs and what it can report: 1.4.0 corrected nested domain ordering and added the first OpenTelemetry integration, and 1.5.0 replaced the R6 promise class with a classed environment while stabilizing the tracing API.
What is xml2?
xml2 relicensed to MIT, then moved its hot accessors from S3 into C
xml2 is the libxml2 binding under most R HTML and XML work, including rvest. Its release cadence is set by libxml2 versions and R CMD check, but two of the last six matter on their own: the 1.3.3 MIT relicense and the 1.3.6 dispatch rewrite that pushed the common accessors into C and dropped three dependencies.
promises vs xml2: editorial side-by-side
promises
0.0DEVOPS
promises drops R6 for plain environments and wires async work into OpenTelemetry
◆ Current state
promises supplies the async primitives behind Shiny and plumber. After years of small domain and future() fixes, the last two releases changed both what a promise costs and what it can report: 1.4.0 corrected nested domain ordering and added the first OpenTelemetry integration, and 1.5.0 replaced the R6 promise class with a classed environment while stabilizing the tracing API.
◆ Where it's heading
Two things are being fixed at once. Promise domains - the mechanism that carries context across async boundaries - have been the source of nearly every bug in this window, and they are now being used deliberately as the vehicle for tracing rather than just for error handling. Meanwhile the object itself is being made cheap enough to create in volume.
◆ Prediction
Expect the OpenTelemetry surface to lose its experimental label and pick up the same span coverage Shiny would need end to end; the deprecated ospan function names should be removed in a following release.
xml2
0.0DEVOPS
xml2 relicensed to MIT, then moved its hot accessors from S3 into C
◆ Current state
xml2 is the libxml2 binding under most R HTML and XML work, including rvest. Its release cadence is set by libxml2 versions and R CMD check, but two of the last six matter on their own: the 1.3.3 MIT relicense and the 1.3.6 dispatch rewrite that pushed the common accessors into C and dropped three dependencies.
◆ Where it's heading
This is infrastructure maintenance in the strict sense - most releases exist because the toolchain moved, not because the package did. Where the maintainers do choose the work, it goes to performance and dependency reduction rather than new API, and the surface has been essentially stable since 1.3.0.
◆ Prediction
Expect the next releases to track libxml2 compatibility and R-devel format-string warnings; new API is unlikely beyond occasional XPath accessors in the style of xml_find_int().
Alternatives to promises and xml2
Other DevOps products tracked by Sparkpulse, ranked by recent ship velocity. Each card links to a full editorial trajectory and lets you pivot into a head-to-head comparison with either promises or xml2.
ellipsis
ellipsis' checks live in rlang now; the package is a compatibility shim.
clock
clock is turning calendar conventions lubridate hard-coded into parameterized types.
httpuv
httpuv ships almost nothing, which is what you want from the web server under Shiny
withr
withr rebuilt defer() on base R's own on.exit(), and got much faster for it
htmltools
htmltools spends three releases walking back its own fill-layout opinions
See all promises alternatives → · See all xml2 alternatives →
Recent activity from promises and xml2
Latest ship moves from both products, interleaved chronologically. ⚡ = editorial spark.
- 9mo agopromisesOpenTelemetry spans across async work; R6 dropped for environments ⚡
- 9mo agopromisesNested promise domains fixed; then() gains a tee argument
- 1y agopromisesRealigns future object creation with the future package
- 1y agopromisesFixes stack overflow on long promise chains
- 1y agopromisesFixes domains forgotten inside nested handlers
- 2y agoxml2Accessors dispatch in C; glue, withr and lifecycle dropped
- 3y agopromisesfuture_promise() returns early when workers are exhausted
- 3y agoxml2Small xml_find_all() speedup and check fixes
- 3y agoxml2R CMD check fixes and a Windows libxml2 bump
- 4y agoxml2Relicensed to MIT, with Hadley Wickham back as maintainer ⚡
- 6y agoxml2Rejects multi-element strings; fixes a raw-input regression
- 6y agoxml2Restores reading HTML with non-ASCII encodings
Frequently asked questions
What is the difference between promises and xml2?
Both compete on the same themes — performance — within DevOps. promises and xml2 are shipping at a similar cadence (velocity 0.0 vs 0.0, both within Sparkpulse's "active" band). See the at-a-glance table above for a side-by-side breakdown of velocity, recent sparks, and editorial themes.
Is promises better than xml2?
Sparkpulse doesn't pick a winner — we score release velocity, not feature parity. promises and xml2 are shipping at a similar cadence (velocity 0.0 vs 0.0, both within Sparkpulse's "active" band). For your specific use case, the alternatives sections above list other DevOps products to evaluate alongside.
What are the best alternatives to promises?
Top promises alternatives in DevOps are ranked by recent ship velocity. Browse the "promises alternatives" section above for the current picks, or visit /alternatives/promises for the full list with editorial commentary on each.
What are the best alternatives to xml2?
Top xml2 alternatives in DevOps are ranked by recent ship velocity. Browse the "xml2 alternatives" section above for the current picks, or visit /alternatives/xml2 for the full list with editorial commentary on each.