net/http: TestServeContent failing on linux-amd64-wsl

[mknyszek]

As of https://golang.org/cl/305230, TestServeContent has started failing on the linux-amd64-wsl builder:

--- FAIL: TestServeContent (0.01s)
    fs_test.go:1086: test "with_last_modified" using "GET": got content-type = "application/xhtml+xml", want "text/html; charset=utf-8"
    fs_test.go:1086: test "with_last_modified" using "HEAD": got content-type = "application/xhtml+xml", want "text/html; charset=utf-8"
FAIL

CC @Jacalz @ianlancetaylor

[gopherbot]

Change https://golang.org/cl/309574 mentions this issue: mime: in globs2 file only keep first time extension is seen

[Jacalz]

Strange. I can't replicate it on my own machine, but it's good to see that there is a fix for it.

[bcmills]

It's not just WSL; it seems to affect a number of the reverse builders:
2021-04-13T14:13:57-4b00eb7/linux-amd64-wsl
2021-04-13T14:13:57-4b00eb7/solaris-amd64-oraclerel
2021-04-13T14:07:17-444d282/linux-amd64-wsl
2021-04-13T14:07:17-444d282/solaris-amd64-oraclerel
2021-04-13T13:56:21-13a4e8c/linux-amd64-wsl
2021-04-13T13:51:17-d948b86/linux-amd64-wsl
2021-04-13T13:51:17-d948b86/solaris-amd64-oraclerel
2021-04-12T22:50:31-49e933f/linux-amd64-wsl
2021-04-12T22:50:31-49e933f/linux-riscv64-jsing
2021-04-12T22:50:31-49e933f/solaris-amd64-oraclerel
2021-04-12T22:19:11-841bc14/linux-amd64-wsl
2021-04-12T22:19:11-841bc14/linux-riscv64-jsing
2021-04-12T22:19:11-841bc14/solaris-amd64-oraclerel
2021-04-12T21:59:59-263e13d/linux-amd64-wsl
2021-04-12T21:59:59-263e13d/linux-riscv64-jsing
2021-04-12T21:59:59-263e13d/solaris-amd64-oraclerel
2021-04-12T21:59:20-3d5e3a1/linux-amd64-wsl
2021-04-12T21:59:20-3d5e3a1/linux-riscv64-jsing
2021-04-12T21:59:20-3d5e3a1/solaris-amd64-oraclerel
2021-04-12T21:58:25-c27991b/linux-amd64-wsl
2021-04-12T21:58:25-c27991b/linux-riscv64-jsing
2021-04-12T21:58:25-c27991b/solaris-amd64-oraclerel
2021-04-12T21:57:23-cccd3ba/linux-amd64-wsl
2021-04-12T21:57:23-cccd3ba/linux-riscv64-jsing
2021-04-12T21:57:23-cccd3ba/solaris-amd64-oraclerel
2021-04-12T21:29:02-aad13cb/linux-amd64-wsl
2021-04-12T21:29:02-aad13cb/linux-riscv64-jsing
2021-04-12T21:29:02-aad13cb/solaris-amd64-oraclerel
2021-04-12T21:26:59-5c9b6e8/linux-amd64-wsl
2021-04-12T21:26:59-5c9b6e8/solaris-amd64-oraclerel
2021-04-12T21:04:48-3e8ba91/linux-amd64-wsl
2021-04-12T21:04:48-3e8ba91/solaris-amd64-oraclerel

[siebenmann]

This also affects Fedora 33 and Ubuntu 20.04, although likely not Ubuntu 18.04. The critical element is what your /usr/share/mime/globs2 (or /usr/local/share/mime/globs2) contains for .html. On a system with the problem, it will have

; fgrep .html globs2
80:text/html:*.html
50:application/xhtml+xml:*.html

It appears whether this happens depends on what version of the /usr/share/mime/packages/freedesktop.org.xml file a system has. Older versions lumped .html and a few other extensions as HTML and text/html; later versions change this to XHTML and application/xhtml+xml, which adds the second globs2 entry for .html.