[BUGZILLA #17543] available.packages attempts to parse 404 response to request for PACKAGES.gz

[MichaelChirico]

If

(1) available.packages is given a non-file repository URL, and
(2) that repository responds to requests for /src/contrib/PACKAGES.rds or /src/contrib/PACKAGES.gz with 404, but /src/contrib/PACKAGES responds normally
(3) method is 'curl', 'libcurl', or not provided on an R with capabilities('libcurl') == TRUE (i.e. defaults to 'libcurl')

then the expected fallback to src/contrib/PACKAGES at src/library/utils/R/packages.R#L113 is skipped, and read.dcf at src/library/utils/R/packages.R#L123 attempts to parse the 404 response to the request for /src/contrib/PACKAGES.gz from the repository, which raises a warning, and skips over that repo entirely.

This is due to curl/libcurl returning a status code of 0 for 4xx responses. At src/library/utils/R/packages.R#L113 z is then 0 and does not inherit from 'error', so the attempt to grab /src/contrib/PACKAGES, which would have succeeded is skipped.

The issue can be resolved by setting options(download.file.extra=c('-f')), which instructs curl to return non-zero status for HTTP response codes >=400.

However, this is unexpected, and appears to run counter to the documented behavior in the Admin manual (https://cran.r-project.org/doc/manuals/R-admin.html#Setting-up-a-package-repository) which implies that the .gz/.rds PACKAGES variants are optional.

Happy to submit a patch as well, if this is indeed a bug.

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METADATA

• Bug author - Andrew Christianson
• Creation time - 2019-03-21 22:46:46 UTC
• Bugzilla link
• Status - UNCONFIRMED
• Alias - None
• Component - Add-ons
• Version - R 3.5.2
• Hardware - x86_64/x64/amd64 (64-bit) OS X El Capitan
• Importance - P5 minor
• Assignee - R-core
• URL -
• Modification time - 2019-03-21 22:47 UTC