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<title>Servant and a weirdness in Keycloak</title>
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<div class="post-date">01 Dec 2024</div><h1 class="post-title"><a href="https://magnus.therning.org/2024-12-01-servant-and-a-weirdness-in-keycloak.html">Servant and a weirdness in Keycloak</a></h1>
<p>
When writing a small tool to interface with Keycloak I found an endpoint that
require the content type to be <code>application/json</code> while the body should be plain
text. (The details are in the <a href="https://github.com/keycloak/keycloak/issues/34401">issue</a>.) Since <a href="https://hackage.haskell.org/package/servant">servant</a> assumes that the content
type and the content match (I know, I'd always thought that was a safe
assumption to make too) it doesn't work with <code>ReqBody '[JSON] Text</code>. Instead I
had to create a custom type that's a combination of <a href="https://hackage.haskell.org/package/servant-0.20.2/docs/Servant-API-ContentTypes.html#t:JSON"><code>JSON</code></a> and <a href="https://hackage.haskell.org/package/servant-0.20.2/docs/Servant-API-ContentTypes.html#t:PlainText"><code>PlainText</code></a>,
something that turned out to required surprisingly little code:
</p>

<div class="org-src-container">
<pre class="src src-haskell"><span class="org-keyword">data</span> KeycloakJSON <span class="org-keyword">deriving</span> <span class="org-rainbow-delimiters-depth-1">(</span>Typeable<span class="org-rainbow-delimiters-depth-1">)</span>

<span class="org-keyword">instance</span> Accept <span class="org-type">KeycloakJSON</span> <span class="org-keyword">where</span>
<span class="org-function-name">contentType</span> _ = <span class="org-string">"application"</span> <span class="org-operator">//</span> <span class="org-string">"json"</span>

<span class="org-keyword">instance</span> MimeRender <span class="org-type">KeycloakJSON</span> <span class="org-type">Text</span> <span class="org-keyword">where</span>
<span class="org-function-name">mimeRender</span> _ = fromStrict <span class="org-operator">.</span> encodeUtf8
</pre>
</div>

<p>
The bug has already been fixed in Keycloak, but I'm sure there are other APIs
with similar weirdness so maybe this will be useful to someone else.
</p>
<div class="taglist"><a href="https://magnus.therning.org/tags.html">Tags</a>: <a href="https://magnus.therning.org/tag-haskell.html">haskell</a> <a href="https://magnus.therning.org/tag-servant.html">servant</a> </div>
<div id="comments">Comment <a href=mailto:[email protected]?subject=Comment%20on%20INSERT%20POST%20URL%20HERE>here</a>.</div></div>
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<div class="post-date">01 Dec 2024</div><h2 class="post-title"><a href="https://magnus.therning.org/2024-12-01-servant-and-a-weirdness-in-keycloak.html">Servant and a weirdness in Keycloak</a></h2>
<div class="post-date">09 Sep 2024</div><h2 class="post-title"><a href="https://magnus.therning.org/2024-09-09-followup-on-secrets-in-my-work-notes.html">Followup on secrets in my work notes</a></h2>
<div class="post-date">01 Sep 2024</div><h2 class="post-title"><a href="https://magnus.therning.org/2024-09-01-improving-how-i-handle-secrets-in-my-work-notes.html">Improving how I handle secrets in my work notes</a></h2>
<div class="post-date">11 Aug 2024</div><h2 class="post-title"><a href="https://magnus.therning.org/2024-08-11-removing-symlink-question.html">Removing symlink question</a></h2>
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<title><![CDATA[Magnus web site - emacs]]></title>
<description><![CDATA[Magnus web site - emacs]]></description>
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<title><![CDATA[Followup on secrets in my work notes]]></title>
<description><![CDATA[
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<title><![CDATA[Magnus web site]]></title>
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<item>
<title><![CDATA[Servant and a weirdness in Keycloak]]></title>
<description><![CDATA[
<p>
When writing a small tool to interface with Keycloak I found an endpoint that
require the content type to be <code>application/json</code> while the body should be plain
text. (The details are in the <a href="https://github.com/keycloak/keycloak/issues/34401">issue</a>.) Since <a href="https://hackage.haskell.org/package/servant">servant</a> assumes that the content
type and the content match (I know, I'd always thought that was a safe
assumption to make too) it doesn't work with <code>ReqBody '[JSON] Text</code>. Instead I
had to create a custom type that's a combination of <a href="https://hackage.haskell.org/package/servant-0.20.2/docs/Servant-API-ContentTypes.html#t:JSON"><code>JSON</code></a> and <a href="https://hackage.haskell.org/package/servant-0.20.2/docs/Servant-API-ContentTypes.html#t:PlainText"><code>PlainText</code></a>,
something that turned out to required surprisingly little code:
</p>
<div class="org-src-container">
<pre class="src src-haskell"><span class="org-keyword">data</span> KeycloakJSON <span class="org-keyword">deriving</span> <span class="org-rainbow-delimiters-depth-1">(</span>Typeable<span class="org-rainbow-delimiters-depth-1">)</span>
<span class="org-keyword">instance</span> Accept <span class="org-type">KeycloakJSON</span> <span class="org-keyword">where</span>
<span class="org-function-name">contentType</span> _ = <span class="org-string">"application"</span> <span class="org-operator">//</span> <span class="org-string">"json"</span>
<span class="org-keyword">instance</span> MimeRender <span class="org-type">KeycloakJSON</span> <span class="org-type">Text</span> <span class="org-keyword">where</span>
<span class="org-function-name">mimeRender</span> _ = fromStrict <span class="org-operator">.</span> encodeUtf8
</pre>
</div>
<p>
The bug has already been fixed in Keycloak, but I'm sure there are other APIs
with similar weirdness so maybe this will be useful to someone else.
</p>
<div class="taglist"><a href="https://magnus.therning.org/tags.html">Tags</a>: <a href="https://magnus.therning.org/tag-haskell.html">haskell</a> <a href="https://magnus.therning.org/tag-servant.html">servant</a> </div>
]]></description>
<category><![CDATA[haskell]]></category>
<category><![CDATA[servant]]></category>
<link>https://magnus.therning.org/2024-12-01-servant-and-a-weirdness-in-keycloak.html</link>
<guid>https://magnus.therning.org/2024-12-01-servant-and-a-weirdness-in-keycloak.html</guid>
<pubDate>Sun, 01 Dec 2024 23:00:00 +0100</pubDate>
</item>
<item>
<title><![CDATA[Followup on secrets in my work notes]]></title>
<description><![CDATA[
Expand Down Expand Up @@ -518,87 +554,5 @@ That's a lot better than using <code>overrideCabal</code>!
<guid>https://magnus.therning.org/2024-04-20-update-to-hackage-revisions-in-nix.html</guid>
<pubDate>Sat, 20 Apr 2024 11:04:00 +0200</pubDate>
</item>
<item>
<title><![CDATA[Hackage revisions in Nix]]></title>
<description><![CDATA[
<p>
Today I got very confused when using <code>callHackageDirect</code> to add the <code>openapi3</code>
package gave me errors like this
</p>
<pre class="example" id="org957ddd8">
&gt; Using Parsec parser
&gt; Configuring openapi3-3.2.3...
&gt; CallStack (from HasCallStack):
&gt; withMetadata, called at libraries/Cabal/Cabal/src/Distribution/Simple/Ut...
&gt; Error: Setup: Encountered missing or private dependencies:
&gt; base &gt;=4.11.1.0 &amp;&amp; &lt;4.18,
&gt; base-compat-batteries &gt;=0.11.1 &amp;&amp; &lt;0.13,
&gt; template-haskell &gt;=2.13.0.0 &amp;&amp; &lt;2.20
</pre>
<p>
When looking at its <a href="https://hackage.haskell.org/package/openapi3-3.2.3">entry on Hackage</a> those weren't the version ranges for the
dependencies. Also, running <code>ghc-pkg list</code> told me that I already had all
required packages at versions matching what Hackage said. So, what's actually
happening here?
</p>
<p>
It took me a while before remembering about <a href="https://hackage.haskell.org/package/openapi3-3.2.3/revisions/">revisions</a> but once I did it was
clear that <code>callHackageDirect</code> always fetches the initial revision of a package
(i.e. it fetches the original tar-ball uploaded by the author). After realising
this it makes perfect sense &#x2013; it's the only revision that's guaranteed to be
there and won't change. However, it would be very useful to be able to pick a
revision that actually builds.
</p>
<p>
I'm not the first one to find this, of course. It's been noted and written about
on the <a href="https://discourse.nixos.org/t/watch-out-hackage-revisions/14588">discource</a> several years ago. What I didn't find though was a way to
influence what revision that's picked. It took a bit of rummaging around in the
<code>nixpkgs</code> code but finally I found two variables that's used in the Hackage
derivation to control this
</p>
<ul class="org-ul">
<li><code>revision</code> - a string with the number of the revision, and</li>
<li><code>editedCabalFile</code> - the SHA256 of the modified Cabal file.</li>
</ul>
<p>
Setting them is done using the <code>overrideCabal</code> function. This is a piece of my
setup for a modified set of Haskell packages:
</p>
<div class="org-src-container">
<pre class="src src-nix"><span class="org-nix-attribute">hl</span> = nixpkgs.haskell.lib.compose;
<span class="org-nix-attribute">hsPkgs</span> = nixpkgs.haskell.packages.ghc963.override <span class="org-rainbow-delimiters-depth-1">{</span>
<span class="org-nix-attribute">overrides</span> = newpkgs: oldpkgs: <span class="org-rainbow-delimiters-depth-2">{</span>
<span class="org-nix-attribute">openapi3</span> = hl.overrideCabal <span class="org-rainbow-delimiters-depth-3">(</span>drv: <span class="org-rainbow-delimiters-depth-4">{</span>
<span class="org-nix-attribute">revision</span> = <span class="org-string">"4"</span>;
<span class="org-nix-attribute">editedCabalFile</span> =
<span class="org-string">"sha256-a5C58iYrL7eAEHCzinICiJpbNTGwiOFFAYik28et7fI="</span>;
<span class="org-rainbow-delimiters-depth-4">}</span><span class="org-rainbow-delimiters-depth-3">)</span> <span class="org-rainbow-delimiters-depth-3">(</span>oldpkgs.callHackageDirect <span class="org-rainbow-delimiters-depth-4">{</span>
<span class="org-nix-attribute">pkg</span> = <span class="org-string">"openapi3"</span>;
<span class="org-nix-attribute">ver</span> = <span class="org-string">"3.2.3"</span>;
<span class="org-nix-attribute">sha256</span> = <span class="org-string">"sha256-0F16o3oqOB5ri6KBdPFEFHB4dv1z+Pw6E5f1rwkqwi8="</span>;
<span class="org-rainbow-delimiters-depth-4">}</span> <span class="org-rainbow-delimiters-depth-4">{</span> <span class="org-rainbow-delimiters-depth-4">}</span><span class="org-rainbow-delimiters-depth-3">)</span>;
</pre>
</div>
<p>
It's not very ergonomic, and I think an extended version of <code>callHackageDirect</code>
would make sense.
</p>
<div class="taglist"><a href="https://magnus.therning.org/tags.html">Tags</a>: <a href="https://magnus.therning.org/tag-haskell.html">haskell</a> <a href="https://magnus.therning.org/tag-nix.html">nix</a> </div>
]]></description>
<category><![CDATA[haskell]]></category>
<category><![CDATA[nix]]></category>
<link>https://magnus.therning.org/2024-03-14-hackage-revisions-in-nix.html</link>
<guid>https://magnus.therning.org/2024-03-14-hackage-revisions-in-nix.html</guid>
<pubDate>Thu, 14 Mar 2024 22:31:00 +0100</pubDate>
</item>
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<div id="preamble" class="status"><div class="nav-bar"><a class="nav-link" href="./index.html">Top</a><a class="nav-link" href="./archive.html">Archive</a><a class="nav-link align-right" href="./feed.xml"><img src="static/rss-feed-icon.png" style="height: 24px;" /></a></div></div>
<div id="content">
<header class="site-header" role="banner"><h1 class="title">Magnus web site</h1><h2 class="subtitle">Random stuff</h2></header>
<div class="post-date">01 Dec 2024</div><h1 class="post-title"><a href="https://magnus.therning.org/2024-12-01-servant-and-a-weirdness-in-keycloak.html">Servant and a weirdness in Keycloak</a></h1>
<p>
When writing a small tool to interface with Keycloak I found an endpoint that
require the content type to be <code>application/json</code> while the body should be plain
text. (The details are in the <a href="https://github.com/keycloak/keycloak/issues/34401">issue</a>.) Since <a href="https://hackage.haskell.org/package/servant">servant</a> assumes that the content
type and the content match (I know, I'd always thought that was a safe
assumption to make too) it doesn't work with <code>ReqBody '[JSON] Text</code>. Instead I
had to create a custom type that's a combination of <a href="https://hackage.haskell.org/package/servant-0.20.2/docs/Servant-API-ContentTypes.html#t:JSON"><code>JSON</code></a> and <a href="https://hackage.haskell.org/package/servant-0.20.2/docs/Servant-API-ContentTypes.html#t:PlainText"><code>PlainText</code></a>,
something that turned out to required surprisingly little code:
</p>

<div class="org-src-container">
<pre class="src src-haskell"><span class="org-keyword">data</span> KeycloakJSON <span class="org-keyword">deriving</span> <span class="org-rainbow-delimiters-depth-1">(</span>Typeable<span class="org-rainbow-delimiters-depth-1">)</span>

<span class="org-keyword">instance</span> Accept <span class="org-type">KeycloakJSON</span> <span class="org-keyword">where</span>
<span class="org-function-name">contentType</span> _ = <span class="org-string">"application"</span> <span class="org-operator">//</span> <span class="org-string">"json"</span>

<span class="org-keyword">instance</span> MimeRender <span class="org-type">KeycloakJSON</span> <span class="org-type">Text</span> <span class="org-keyword">where</span>
<span class="org-function-name">mimeRender</span> _ = fromStrict <span class="org-operator">.</span> encodeUtf8
</pre>
</div>

<p>
The bug has already been fixed in Keycloak, but I'm sure there are other APIs
with similar weirdness so maybe this will be useful to someone else.
</p>
<div class="taglist"><a href="https://magnus.therning.org/tags.html">Tags</a>: <a href="https://magnus.therning.org/tag-haskell.html">haskell</a> <a href="https://magnus.therning.org/tag-servant.html">servant</a> </div>

<div class="post-date">09 Sep 2024</div><h1 class="post-title"><a href="https://magnus.therning.org/2024-09-09-followup-on-secrets-in-my-work-notes.html">Followup on secrets in my work notes</a></h1>
<p>
I got the following question on my post on how I handle secrets in my work notes:
Expand Down Expand Up @@ -210,44 +238,6 @@
community cache. Perfect!
</p>
<div class="taglist"><a href="https://magnus.therning.org/tags.html">Tags</a>: <a href="https://magnus.therning.org/tag-emacs.html">emacs</a> <a href="https://magnus.therning.org/tag-nix.html">nix</a> </div>

<div class="post-date">13 Jul 2024</div><h1 class="post-title"><a href="https://magnus.therning.org/2024-07-13-hoogle-setup-for-local-development.html">Hoogle setup for local development</a></h1>
<p>
About a week ago I asked a <a href="https://discourse.nixos.org/t/haskell-shell-setup-with-working-hoogle-developpackage/48507/2">question on the Nix Discourse</a> about how to create a
setup for Hoogle that
</p>

<ul class="org-ul">
<li>includes the locally installed packages, and</li>
<li>the package I'm working on, and ideally also</li>
<li>have all local links, i.e. no links to <a href="https://hackage.haskell.org/">Hackage</a>.</li>
</ul>

<p>
I didn't get an answer there, but some people on the Nix Haskell channel on
Matrix helped a bit, but it seems this particular use case requires a bit of
manual work. The following commands get me an almost fully working setup:
</p>

<div class="org-src-container">
<pre class="src src-shell">cabal haddock --haddock-internal --haddock-quickjump --haddock-hoogle --haddock-html

<span class="org-variable-name">hoogle_dir</span>=$<span class="org-rainbow-delimiters-depth-1">(</span>dirname $<span class="org-rainbow-delimiters-depth-2">(</span>dirname $<span class="org-rainbow-delimiters-depth-3">(</span>readlink -f $<span class="org-rainbow-delimiters-depth-4">(</span><span class="org-builtin">which</span> hoogle<span class="org-rainbow-delimiters-depth-4">)</span><span class="org-rainbow-delimiters-depth-3">)</span><span class="org-rainbow-delimiters-depth-2">)</span><span class="org-rainbow-delimiters-depth-1">)</span>
hoogle generate --database=local.hoo <span class="org-sh-escaped-newline">\</span>
$<span class="org-rainbow-delimiters-depth-1">(</span><span class="org-keyword">for</span> d<span class="org-keyword"> in</span> $<span class="org-rainbow-delimiters-depth-2">(</span>fd -L .txt $<span class="org-rainbow-delimiters-depth-3">{</span><span class="org-variable-name">hoogle_dir</span><span class="org-rainbow-delimiters-depth-3">}</span><span class="org-rainbow-delimiters-depth-2">)</span>; <span class="org-keyword">do</span> printf <span class="org-string">"--local=%s "</span> $<span class="org-rainbow-delimiters-depth-2">(</span>dirname $<span class="org-variable-name">d</span><span class="org-rainbow-delimiters-depth-2">)</span>; <span class="org-keyword">done</span><span class="org-rainbow-delimiters-depth-1">)</span> <span class="org-sh-escaped-newline">\</span>
--local=./dist-newstyle/build/x86_64-linux/ghc-9.8.2/pkg-0.0.1/doc/html/pkg

hoogle server --local --database=local.foo
</pre>
</div>

<p>
What's missing is working links between the documentation of locally installed
packages. It looks like the links in the generated documention in Nix have a lot
of relative references containing <code>${pkgroot}/../../../../</code> which is what I
supect causes the broken links.
</p>
<div class="taglist"><a href="https://magnus.therning.org/tags.html">Tags</a>: <a href="https://magnus.therning.org/tag-haskell.html">haskell</a> <a href="https://magnus.therning.org/tag-nix.html">nix</a> </div>
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