Make user-agent for linkchecks customisable

CHANGELOG.md

@@ -3,7 +3,11 @@
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## UNRELEASED
+## UNRELEASD
+
+### Added
+
+* The `User-Agent` header set in the linkcheck HTTP(S) requests can now be customized with the `linkcheck_useragent` option to `makedocs`. ([#2557], [#2562])
 
 ### Fixed
 
@@ -1880,8 +1884,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 [#2514]: https://github.com/JuliaDocs/Documenter.jl/issues/2514
 [#2549]: https://github.com/JuliaDocs/Documenter.jl/issues/2549
 [#2551]: https://github.com/JuliaDocs/Documenter.jl/issues/2551
+[#2557]: https://github.com/JuliaDocs/Documenter.jl/issues/2557
 [#2560]: https://github.com/JuliaDocs/Documenter.jl/issues/2560
 [#2561]: https://github.com/JuliaDocs/Documenter.jl/issues/2561
+[#2562]: https://github.com/JuliaDocs/Documenter.jl/issues/2562
 [JuliaLang/julia#36953]: https://github.com/JuliaLang/julia/issues/36953
 [JuliaLang/julia#38054]: https://github.com/JuliaLang/julia/issues/38054
 [JuliaLang/julia#39841]: https://github.com/JuliaLang/julia/issues/39841

src/docchecks.jl

@@ -191,6 +191,8 @@
     return nothing
 end
 
+const _LINKCHECK_DEFAULT_USERAGENT = "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.103 Safari/537.36"
+
 function linkcheck(node::MarkdownAST.Node, link::MarkdownAST.Link, doc::Document; method::Symbol=:HEAD)
 
     # first, make sure we're not supposed to ignore this link
@@ -203,6 +205,7 @@
 
     if !haskey(doc.internal.locallinks, link)
         timeout = doc.user.linkcheck_timeout
+        useragent = doc.user.linkcheck_useragent
         null_file = @static Sys.iswindows() ? "nul" : "/dev/null"
         # In some cases, web servers (e.g. docs.github.com as of 2022) will reject requests
         # that declare a non-browser user agent (curl specifically passes 'curl/X.Y'). In
@@ -212,12 +215,17 @@
         # Mozilla developer docs, but only is it's a HTTP(S) request.
         #
         # https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/User-Agent#chrome_ua_string
-        fakebrowser  = startswith(uppercase(link.destination), "HTTP") ? [
-            "--user-agent",
-            "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.103 Safari/537.36",
-            "-H",
-            "accept-encoding: gzip, deflate, br",
-        ] : ""
+        fakebrowser  = if startswith(uppercase(link.destination), "HTTP")
+            headers = [
+                "-H",
+                "accept-encoding: gzip, deflate, br",
+            ]
+            if !isempty(useragent)
+                push!(headers, "--user-agent", useragent)
+            end
+        else
+            ""
+        end
         cmd = `curl $(method === :HEAD ? "-sI" : "-s") --proto =http,https,ftp,ftps $(fakebrowser) $(link.destination) --max-time $timeout -o $null_file --write-out "%{http_code} %{url_effective} %{redirect_url}"`
 
         local result

src/documents.jl

@@ -312,6 +312,7 @@ struct User
     linkcheck::Bool           # Check external links..
     linkcheck_ignore::Vector{Union{String,Regex}}  # ..and then ignore (some of) them.
     linkcheck_timeout::Real   # ..but only wait this many seconds for each one.
+    linkcheck_useragent::String  # User agent to use for linkchecks.
     checkdocs::Symbol         # Check objects missing from `@docs` blocks. `:none`, `:exports`, or `:all`.
     doctestfilters::Vector{Regex} # Filtering for doctests
     warnonly::Vector{Symbol}  # List of docerror groups that should only warn, rather than cause a build failure
@@ -385,6 +386,7 @@ function Document(;
         linkcheck:: Bool             = false,
         linkcheck_ignore :: Vector   = [],
         linkcheck_timeout :: Real    = 10,
+        linkcheck_useragent :: String= _LINKCHECK_DEFAULT_USERAGENT,
         checkdocs::Symbol            = :all,
         doctestfilters::Vector{Regex}= Regex[],
         warnonly :: Union{Bool,Symbol,Vector{Symbol}} = Symbol[],
@@ -450,6 +452,7 @@ function Document(;
         linkcheck,
         linkcheck_ignore,
         linkcheck_timeout,
+        linkcheck_useragent,
         checkdocs,
         doctestfilters,
         warnonly,

src/makedocs.jl

@@ -192,6 +192,18 @@ ignored.
 **`linkcheck_timeout`** configures how long `curl` waits (in seconds) for a link request to
 return a response before giving up. The default is 10 seconds.
 
+**`linkcheck_useragent`** can be used to override the user agent string used by the HTTP and
+HTTPS requests made when checking for broken links. Currently, the default user agent is
+
+```
+$(_LINKCHECK_DEFAULT_USERAGENT)
+```
+
+which is set to mimic a realistic web browser. However, the exact user agent string is subject
+to change. As such, it is possible that breakages can occur when Documenter's version changes,
+but the goal is to set the user agent such that it would be accepted by as many web servers as
+possible.
+
 **`warnonly`** can be used to control whether the `makedocs` build fails with an error, or
 simply prints a warning if it detects any issues with the document. Additionally, a `Symbol`
 or a `Vector` of `Symbol`s can be passed to make Documenter warn for only those specified

test/examples/make.jl

@@ -416,6 +416,7 @@ examples_html_local_doc = if "html-local" in EXAMPLE_BUILDS
         repo = "https://dev.azure.com/org/project/_git/repo?path={path}&version={commit}{line}&lineStartColumn=1&lineEndColumn=1",
         linkcheck = true,
         linkcheck_ignore = [r"(x|y).md", "z.md", r":func:.*"],
+        linkcheck_useragent = "Documenter/1",
         format = Documenter.HTML(
             assets = [
                 "assets/custom.css",
@@ -434,7 +435,7 @@ else
 end
 
 # HTML: draft mode
-examples_html_local_doc = if "html-draft" in EXAMPLE_BUILDS
+examples_html_draft_doc = if "html-draft" in EXAMPLE_BUILDS
     @info("Building mock package docs: HTMLWriter / draft build")
     @quietly makedocs(
         debug = true,

test/examples/tests.jl

@@ -363,6 +363,9 @@ end
             # .. but, crucially, Main.SVG_HTML did _not_ get written out.
             @test !isfile(joinpath(build_dir, "example-output", "$(SVG_BIG.hash_slug)-002.svg"))
         end
+
+        # Testing linkcheck_useragent default
+        @test doc.user.linkcheck_useragent == Documenter._LINKCHECK_DEFAULT_USERAGENT
     end
 
     @testset "HTML: local" begin
@@ -421,6 +424,10 @@ end
             # .. but, crucially, Main.SVG_HTML did _not_ get written out.
             @test !isfile(joinpath(build_dir, "example-output-$(SVG_BIG.hash_slug)-002.svg"))
         end
+
+        # It doesn't actually test that the user agent was used correctly, but at least it tests that
+        # the option go set.
+        @test doc.user.linkcheck_useragent == "Documenter/1"
     end
 
     @testset "HTML: pagesonly" begin