Add doc/manual, tweak README

README.md

@@ -4,10 +4,9 @@
 *Wait, what?*
 
 With Arion you can fire up containers without creating images for each
-service. Instead, it uses a mostly empty image, sort of like a base
+service. It can use a mostly empty image, and makes the host's Nix
-image, and makes the host's Nix store available in the container,
+store available in the container, allowing the container to run
-allowing the container to run programs without having to re-package
+programs without having to re-package them into a docker image.
-them into a docker image.
 
 Arion is configured using Nix with modules, like those in
 NixOS. Similar to `docker-compose` it can therefore combine
@@ -21,13 +20,10 @@ development environments while working
 on [Hercules CI](https://www.hercules-ci.com). (It was also born out
 of ancient Greek deities disguised as horses. More on that later.)
 
-We don't use it to deploy to 'real' environments and we have no plans
+If you do want to use Arion for production environments, you'll
-to do so in the future.
+probably want to either build normal container images or manage
-
+garbage collection roots if you control the deployment host. Neither
-If you do want to use Arion for 'real' environments, you'll probably
+scenario is made easier by arion at this time.
-want to either build images or manage garbage collection roots if you
-control the deployment host. Either of these has yet to be
-implemented.
 
 Support for other Linux than NixOS is untested.
 
@@ -68,7 +64,7 @@ This Nix expression serves the Nix manual at host port 8000 when launched with `
 }
 ```
 
-The `pkgs` argument comes from a file called `arion-pkgs.nix`. It can be as simple as `import <nixpkgs> {}` to use the Nixpkgs from your `$NIX_PATH`.
+The `pkgs` argument comes from a file called `arion-pkgs.nix`. It can be as simple as `import <nixpkgs> {}` to use the Nixpkgs from your `$NIX_PATH`, or you can use it to pin a specific Nixpkgs version.
 
 # A full featured example
 
@@ -90,7 +86,7 @@ When it runs, it does the following:
 Most of the interesting stuff happens in Arion's Nix expressions,
 where it runs the module system (known from NixOS) and provides the configuration that makes the Docker Compose file do the things it needs to do.
 
-The interesting part is of course the [service-host-store.nix module](src/nix/service-host-store.nix) which performs the bind mounts to make the host Nix store available in the container.
+One of the more interesting built-in modules is the [host-store.nix module](src/nix/modules/service/host-store.nix) which performs the bind mounts to make the host Nix store available in the container.
 
 # FAQ
 
@@ -101,7 +97,7 @@ Nope, it's just Nix and Docker Compose under the hood.
 
 ### Does Arion support Docker images?
 
-Yes, you can still specify a docker image. For example:
+Yes, you can also specify a normal Docker image. For example:
 
     postgres = {
       service.image = "postgres:10";

default.nix

@@ -2,4 +2,5 @@ args@{ pkgs ? import ./nix args, ... }:
 
 {
   inherit (pkgs) arion tests;
+  doc = pkgs.recurseIntoAttrs (import ./doc { inherit pkgs; });
 }

doc/default.nix

@@ -0,0 +1,8 @@
+{ pkgs ? import ../nix {} }:
+let
+  inherit (pkgs) recurseIntoAttrs callPackage;
+in
+
+recurseIntoAttrs {
+  manual = callPackage ./manual {};
+}

doc/manual/.gitignore

@@ -0,0 +1,4 @@
+introduction.xml
+manual.html
+options-composition.xml
+options-service.xml

doc/manual/Makefile

@@ -0,0 +1,35 @@
+xsltproc = xsltproc --nonet \
+ --param section.autolabel 0 \
+ --param section.label.includes.component.label 0 \
+ --param chapter.autolabel 0 \
+ --param chapter.label.includes.component.label 0 \
+ --param appendix.autolabel 0 \
+ --param appendix.label.includes.component.label 0 \
+ --param generate.toc "'book toc,title chapter nop section nop sect1 nop sect2 nop sect3 nop sect4 nop sect5 nop'" \
+ --param html.stylesheet \'style.css\' \
+ --param xref.with.number.and.title 0 \
+ --param toc.section.depth 3 \
+ --param admon.style \'\' \
+ --param callout.graphics.extension \'.gif\' \
+ --param contrib.inline.enabled 0
+
+docbookxsl = http://docbook.sourceforge.net/release/xsl/current
+
+all: manual.html
+
+manual.html: manual.xml introduction.xml installation.xml options-composition.xml options-service.xml
+	$(xsltproc) --xinclude --stringparam profile.condition manual \
+	  $(docbookxsl)/profiling/profile.xsl manual.xml | \
+	  $(xsltproc) --output manual.html $(docbookxsl)/xhtml/docbook.xsl -
+
+# -e 's_<book lang="en">__' -e 's_</book>__'
+%.xml: %.asciidoc
+	asciidoctor --backend docbook45 --doctype article $<
+	sed -e 's/<!DOCTYPE.*//' -e 's/<?asciidoc-[a-z]*?>//' -i $@
+
+options-composition.xml options-service.xml:
+	echo "options-composition.xml and options-service.xml should be written by the derivation. Are you running in 'nix-shell -A manual'?"; exit 1; fi
+
+install: all
+	mkdir -p $(docdir)
+	cp manual.html style.css $(docdir)

doc/manual/default.nix

@@ -0,0 +1,120 @@
+{ pkgs ? import ../../nix {}
+, version ? "none"
+# Default sourceUrl is for local development. Works with
+#   nix-build -A doc.manual
+# For release, use: https://github.com/hercules-ci/arion/blob/${version}
+, sourceUrl ? "../../.."
+}:
+let
+  inherit (pkgs) recurseIntoAttrs callPackage runCommand lib stdenv ;
+
+  nixosManualPath = s: "${pkgs.path}/nixos/doc/manual/${s}";
+
+  # NixOS module system options in JSON format.
+  options = { moduleType, description, /*optionsList*/ optionsExpr }: recurseIntoAttrs rec {
+    optionsXML =
+      # builtins.toFile "options.xml" (builtins.toXML optionsList);
+      pkgs.runCommand "options.xml" {
+        buildInputs = [pkgs.nix pkgs.fakeroot pkgs.jq];
+        inherit optionsExpr;
+      } ''
+        export NIX_LOG_DIR=$PWD
+        export NIX_STATE_DIR=$PWD
+        nix-instantiate --option sandbox false --readonly-mode --eval --expr "$optionsExpr" --xml --strict >$out
+      '';
+
+    optionsDocBook = runCommand "options-db.xml" {} ''
+      optionsXML=${optionsXML}
+      ${pkgs.buildPackages.libxslt.bin}/bin/xsltproc \
+        --stringparam revision '${version}' \
+        --stringparam sourceUrl '${sourceUrl}' \
+        -o intermediate.xml ${./options-to-docbook.xsl} $optionsXML
+      ${pkgs.buildPackages.libxslt.bin}/bin/xsltproc \
+        -o "$out" ${nixosManualPath "postprocess-option-descriptions.xsl"} intermediate.xml
+    '';
+  };
+
+in
+
+recurseIntoAttrs rec {
+  compositionOptions = options {
+    moduleType = "composition";
+    description = "List of Arion composition-level options in JSON format";
+    optionsExpr = let
+      src = ../../src/nix;
+    in ''
+      let pkgs = import ${pkgs.path} {};
+          fixPaths = opt: opt // {
+            declarations = map (d: "src/nix" + (lib.strings.removePrefix (toString ${src}) (toString d))) opt.declarations;
+          };
+          inherit (pkgs) lib;
+          composition = import ${src}/eval-composition.nix { inherit pkgs; };
+      in map fixPaths (lib.filter (opt: opt.visible && !opt.internal) (lib.optionAttrSetToDocList composition.options))
+    '';
+  };
+  serviceOptions = options {
+    moduleType = "service";
+    description = "List of Arion service-level options in JSON format";
+    optionsExpr = let
+      src = ../../src/nix;
+    in ''
+      let pkgs = import ${pkgs.path} {};
+          fixPaths = opt: opt // {
+            declarations = map (d: "src/nix" + (lib.strings.removePrefix (toString ${src}) (toString d))) opt.declarations;
+          };
+          inherit (pkgs) lib;
+          composition = pkgs.callPackage ${src}/eval-service.nix {} { modules = []; host = {}; };
+      in map fixPaths (lib.filter (opt: opt.visible && !opt.internal) (lib.optionAttrSetToDocList composition.options))
+    '';
+  };
+  generatedDocBook = runCommand "generated-docbook" {} ''
+    mkdir $out
+    ln -s ${compositionOptions.optionsDocBook} $out/options-composition.xml
+    ln -s ${serviceOptions.optionsDocBook} $out/options-service.xml
+  '';
+  manual = stdenv.mkDerivation {
+    src = lib.sourceByRegex ./. [
+      "Makefile$"
+      ".*\.asciidoc$"
+      ".*\.xsl$"
+      ".*\.css$"
+      "^manual.xml$"
+      "^manual.xml$"
+    ];
+    name = "arion-manual";
+    version = version;
+    buildInputs = [
+      (pkgs.libxslt.bin or pkgs.libxslt)
+      pkgs.asciidoctor
+    ];
+    XML_CATALOG_FILES = "${pkgs.docbook_xsl}/xml/xsl/docbook/catalog.xml";
+    inherit generatedDocBook;
+    configurePhase = ''
+      export docdir=$out/doc
+    '';
+    postPatch = ''
+      substituteInPlace manual.xml --subst-var version
+    '';
+    prePatch = ''
+      cp ${generatedDocBook}/* .
+      substituteInPlace options-service.xml \
+        --replace 'xml:id="appendix-configuration-options"' 'xml:id="appendix-service-options"' \
+        --replace '<title>Configuration Options</title>' '<title>Service Options</title>' \
+        --replace 'xml:id="configuration-variable-list"' 'xml:id="service-variable-list"' \
+        ;
+      substituteInPlace options-composition.xml \
+        --replace 'xml:id="appendix-configuration-options"' 'xml:id="appendix-composition-options"' \
+        --replace '<title>Configuration Options</title>' '<title>Composition Options</title>' \
+        --replace 'xml:id="configuration-variable-list"' 'xml:id="composition-variable-list"' \
+        ;
+    '';
+    shellHook = ''
+      live-build() {
+        patchPhase
+        inotifywait -e MODIFY -m -r . | while read; do
+          make
+        done
+      }
+    '';
+  };
+}

doc/manual/installation.asciidoc

@@ -0,0 +1,37 @@
+
+= Installation
+
+== Imperative installation, bleeding edge
+
+```
+git clone git@github.com:hercules-ci/arion.git
+cd arion
+nix-env -iA arion -f .
+```
+
+// TODO: replace the above with something like below
+////
+
+== Not installing: use it in a project
+
+TODO: describe: using nix-shell or in a script, building images as
+      part of nix-build, pinning, see also todomvc-nix.
+
+== Mac or traditional Linux
+
+```
+nix-env -iA nixpkgs.arion
+```
+
+== NixOS
+
+Add this module to your NixOS configuration:
+
+```
+{ pkgs, ... } {
+  virtualisation.docker.enable = true;
+  environment.systemPackages = [ pkgs.arion ];
+}
+```
+
+////

doc/manual/introduction.asciidoc

@@ -0,0 +1,33 @@
+
+= Introduction
+
+Arion is a tool for building and running applications that
+consist of multiple docker containers. It has special support
+for docker images that are built with Nix, for a smooth
+development experience and improved performance.
+
+It is built on top of https://docs.docker.com/compose/overview/[Docker
+Compose], which implements the container orchestration functionality.
+
+Instead of configuring the compositions in YAML files like
+`docker-compose.yaml`, Arion uses the https://nixos.org/nix/[Nix]
+language to declare the compositions. Because of this, Arion gives you
+the ability to declare your deployments, configuration and packaging
+in the same language. By replacing multiple tools with a single
+language, you decrease your mental load and you can more easily
+refactor and maintain your configurations.
+
+Although Arion can be used as a Docker Compose with an improved
+configuration front end, there is more to be gained from integrating
+with Nix. In particular, the more structured approach of Nix compared
+to Dockerfiles allows the following:
+
+ * Build components of your image in _parallel, automatically_.
+ * Share packages between images, regardless of the order they were
+   added.
+ * Improve performance by _skipping_ container
+   image creation.
+ * Work with _structured data_ instead of strings,
+   templates and a multitude of expression languages.
+ * Refactor across deployments, configuration and
+   packaging.

doc/manual/live-build

@@ -0,0 +1,3 @@
+#!/usr/bin/env nix-shell
+#!nix-shell -A manual
+#!nix-shell --run live-build

doc/manual/manual.xml

@@ -0,0 +1,25 @@
+<book xmlns="http://docbook.org/ns/docbook"
+      xmlns:xlink="http://www.w3.org/1999/xlink"
+      xmlns:xi="http://www.w3.org/2001/XInclude">
+
+  <info>
+
+    <title>Arion Manual</title>
+    <subtitle>Version none</subtitle>
+
+    <author>
+      <affiliation>
+        <orgname>Hercules Labs and other Arion contributors</orgname>
+      </affiliation>
+      <contrib>Author</contrib>
+    </author>
+
+  </info>
+
+  <xi:include href="introduction.xml" xpointer="xpointer(/article)" />
+  <xi:include href="installation.xml" xpointer="xpointer(/article)" />
+
+  <xi:include href="options-composition.xml" />
+  <xi:include href="options-service.xml" />
+
+</book>

doc/manual/options-to-docbook.xsl

@@ -0,0 +1,224 @@
+<?xml version="1.0"?>
+
+<xsl:stylesheet version="1.0"
+                xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
+                xmlns:str="http://exslt.org/strings"
+                xmlns:xlink="http://www.w3.org/1999/xlink"
+                xmlns:nixos="tag:nixos.org"
+                xmlns="http://docbook.org/ns/docbook"
+                extension-element-prefixes="str"
+                >
+
+  <xsl:output method='xml' encoding="UTF-8" />
+
+  <xsl:param name="revision" />
+  <xsl:param name="program" />
+  <xsl:param name="sourceUrl" />
+  <xsl:param name="nixPathKey" />
+
+  <xsl:template match="/expr/list">
+    <appendix xml:id="appendix-configuration-options">
+      <title>Configuration Options</title>
+      <variablelist xml:id="configuration-variable-list">
+        <xsl:for-each select="attrs">
+          <xsl:variable name="id" select="concat('opt-', str:replace(str:replace(str:replace(str:replace(attr[@name = 'name']/string/@value, '*', '_'), '&lt;', '_'), '>', '_'), '?', '_'))" />
+          <varlistentry>
+            <term xlink:href="#{$id}">
+              <xsl:attribute name="xml:id"><xsl:value-of select="$id"/></xsl:attribute>
+              <option>
+                <xsl:value-of select="attr[@name = 'name']/string/@value" />
+              </option>
+            </term>
+
+            <listitem>
+
+              <nixos:option-description>
+                <para>
+                  <xsl:value-of disable-output-escaping="yes"
+                                select="attr[@name = 'description']/string/@value" />
+                </para>
+              </nixos:option-description>
+
+              <xsl:if test="attr[@name = 'type']">
+                <para>
+                  <emphasis>Type:</emphasis>
+                  <xsl:text> </xsl:text>
+                  <xsl:value-of select="attr[@name = 'type']/string/@value"/>
+                  <xsl:if test="attr[@name = 'readOnly']/bool/@value = 'true'">
+                    <xsl:text> </xsl:text>
+                    <emphasis>(read only)</emphasis>
+                  </xsl:if>
+                </para>
+              </xsl:if>
+
+              <xsl:if test="attr[@name = 'default']">
+                <para>
+                  <emphasis>Default:</emphasis>
+                  <xsl:text> </xsl:text>
+                  <xsl:apply-templates select="attr[@name = 'default']" mode="top" />
+                </para>
+              </xsl:if>
+
+              <xsl:if test="attr[@name = 'example']">
+                <para>
+                  <emphasis>Example:</emphasis>
+                  <xsl:text> </xsl:text>
+                  <xsl:choose>
+                    <xsl:when test="attr[@name = 'example']/attrs[attr[@name = '_type' and string[@value = 'literalExample']]]">
+                      <programlisting><xsl:value-of select="attr[@name = 'example']/attrs/attr[@name = 'text']/string/@value" /></programlisting>
+                    </xsl:when>
+                    <xsl:otherwise>
+                      <xsl:apply-templates select="attr[@name = 'example']" mode="top" />
+                    </xsl:otherwise>
+                  </xsl:choose>
+                </para>
+              </xsl:if>
+
+              <xsl:if test="attr[@name = 'relatedPackages']">
+                <para>
+                  <emphasis>Related packages:</emphasis>
+                  <xsl:text> </xsl:text>
+                  <xsl:value-of disable-output-escaping="yes"
+                                select="attr[@name = 'relatedPackages']/string/@value" />
+                </para>
+              </xsl:if>
+
+              <xsl:if test="count(attr[@name = 'declarations']/list/*) != 0">
+                <para>
+                  <emphasis>Declared by:</emphasis>
+                </para>
+                <xsl:apply-templates select="attr[@name = 'declarations']" />
+              </xsl:if>
+
+              <xsl:if test="count(attr[@name = 'definitions']/list/*) != 0">
+                <para>
+                  <emphasis>Defined by:</emphasis>
+                </para>
+                <xsl:apply-templates select="attr[@name = 'definitions']" />
+              </xsl:if>
+
+            </listitem>
+
+          </varlistentry>
+
+        </xsl:for-each>
+
+      </variablelist>
+    </appendix>
+  </xsl:template>
+
+
+  <xsl:template match="*" mode="top">
+    <xsl:choose>
+      <xsl:when test="string[contains(@value, '&#010;')]">
+<programlisting>
+<xsl:text>''
+</xsl:text><xsl:value-of select='str:replace(string/@value, "${", "&apos;&apos;${")' /><xsl:text>''</xsl:text></programlisting>
+      </xsl:when>
+      <xsl:otherwise>
+        <literal><xsl:apply-templates /></literal>
+      </xsl:otherwise>
+    </xsl:choose>
+  </xsl:template>
+
+
+  <xsl:template match="null">
+    <xsl:text>null</xsl:text>
+  </xsl:template>
+
+
+  <xsl:template match="string">
+    <xsl:choose>
+      <xsl:when test="(contains(@value, '&quot;') or contains(@value, '\')) and not(contains(@value, '&#010;'))">
+        <xsl:text>''</xsl:text><xsl:value-of select='str:replace(@value, "${", "&apos;&apos;${")' /><xsl:text>''</xsl:text>
+      </xsl:when>
+      <xsl:otherwise>
+        <xsl:text>"</xsl:text><xsl:value-of select="str:replace(str:replace(str:replace(str:replace(@value, '\', '\\'), '&quot;', '\&quot;'), '&#010;', '\n'), '$', '\$')" /><xsl:text>"</xsl:text>
+      </xsl:otherwise>
+    </xsl:choose>
+  </xsl:template>
+
+
+  <xsl:template match="int">
+    <xsl:value-of select="@value" />
+  </xsl:template>
+
+
+  <xsl:template match="bool[@value = 'true']">
+    <xsl:text>true</xsl:text>
+  </xsl:template>
+
+
+  <xsl:template match="bool[@value = 'false']">
+    <xsl:text>false</xsl:text>
+  </xsl:template>
+
+
+  <xsl:template match="list">
+    [
+    <xsl:for-each select="*">
+      <xsl:apply-templates select="." />
+      <xsl:text> </xsl:text>
+    </xsl:for-each>
+    ]
+  </xsl:template>
+
+
+  <xsl:template match="attrs[attr[@name = '_type' and string[@value = 'literalExample']]]">
+    <xsl:value-of select="attr[@name = 'text']/string/@value" />
+  </xsl:template>
+
+
+  <xsl:template match="attrs">
+    {
+    <xsl:for-each select="attr">
+      <xsl:value-of select="@name" />
+      <xsl:text> = </xsl:text>
+      <xsl:apply-templates select="*" /><xsl:text>; </xsl:text>
+    </xsl:for-each>
+    }
+  </xsl:template>
+
+
+  <xsl:template match="derivation">
+    <replaceable>(build of <xsl:value-of select="attr[@name = 'name']/string/@value" />)</replaceable>
+  </xsl:template>
+
+  <xsl:template match="attr[@name = 'declarations' or @name = 'definitions']">
+    <simplelist>
+      <xsl:for-each select="list/string">
+        <member><filename>
+          <!-- Hyperlink the filename either to the NixOS Subversion
+          repository (if it’s a module and we have a revision number),
+          or to the local filesystem. -->
+          <xsl:choose>
+            <xsl:when test="not(starts-with(@value, '/'))">
+              <xsl:attribute name="xlink:href"><xsl:value-of select="$sourceUrl"/>/<xsl:value-of select="@value"/></xsl:attribute>
+            </xsl:when>
+            <xsl:otherwise>
+              <xsl:attribute name="xlink:href">file://<xsl:value-of select="@value"/></xsl:attribute>
+            </xsl:otherwise>
+          </xsl:choose>
+          <!-- Print the filename and make it user-friendly by replacing the
+          /nix/store/<hash> prefix by the default location of nixos
+          sources. -->
+          <xsl:choose>
+            <xsl:when test="$nixPathKey != ''">
+              &lt;<xsl:value-of select="$nixPathKey"/>/<xsl:value-of select="@value"/>&gt;
+            </xsl:when>
+            <xsl:otherwise>
+              <xsl:value-of select="@value" />
+            </xsl:otherwise>
+          </xsl:choose>
+        </filename></member>
+      </xsl:for-each>
+    </simplelist>
+  </xsl:template>
+
+
+  <xsl:template match="function">
+    <xsl:text>λ</xsl:text>
+  </xsl:template>
+
+
+</xsl:stylesheet>

doc/manual/style.css

@@ -0,0 +1,159 @@
+
+hr { color: #ddd; margin-top: 3ex; }
+h1, h2, h3, h4 { font-weight: bold; }
+h1 { font-size: 200%; margin-top: 5ex; }
+h2 { font-size: 160%; margin-top: 4ex; }
+h3,h4 { font-size: 120%; margin-top: 3ex; }
+
+/* From Semantic UI */
+body {
+  font-family: Lato,'Helvetica Neue',Arial,Helvetica,sans-serif;
+  font-size: 14px;
+  line-height: 1.4285em;
+  color: rgba(0,0,0,.87);
+}
+
+code.literal {
+    background-color: #f7f7f7;
+}
+
+a {
+ background-color:transparent;
+ -webkit-text-decoration-skip:objects
+}
+a {
+ color:#4183c4;
+ text-decoration:none
+}
+a:hover {
+ color:#1e70bf;
+ text-decoration:none
+}
+::-webkit-selection {
+ background-color:#cce2ff;
+ color:rgba(0,0,0,.87)
+}
+::-moz-selection {
+ background-color:#cce2ff;
+ color:rgba(0,0,0,.87)
+}
+::selection {
+ background-color:#cce2ff;
+ color:rgba(0,0,0,.87)
+}
+
+/* toc menu */
+@media screen and (min-width: 60em) {
+  body {
+    margin-left: 16.5em; 
+  }
+  div.toc {
+    position: fixed;
+    top: 0pt;
+    left: 1em;
+    height: 100%;
+    overflow-y: auto;
+    width: 15.5em;
+  }
+}
+@media screen and (min-width: 90em) {
+  div.toc {
+    left: 5em;
+  }
+}
+/* hide per chapter toc */
+div.chapter div.toc {
+    display: none;
+}
+
+
+/* From Nixpkgs: */
+
+div.book
+{
+    text-align: center;
+}
+
+div.book > div
+{
+    /*
+     * based on https://medium.com/@zkareemz/golden-ratio-62b3b6d4282a
+     * we do 70 characters per line to fit code listings better
+     * 70 * (font-size / 1.618)
+     * expression for emacs:
+     * (* 70 (/ 1 1.618))
+     */
+    max-width: 43.2em;
+    text-align: left;
+    margin: auto;
+}
+
+
+/***************************************************************************
+                               Special elements:
+ ***************************************************************************/
+
+.term
+{
+    font-weight: bold;
+
+}
+
+div.variablelist dd p, div.glosslist dd p
+{
+    margin-top: 0em;
+}
+
+div.variablelist dd, div.glosslist dd
+{
+    margin-left: 1.5em;
+}
+
+div.glosslist dt
+{
+    font-style: italic;
+}
+
+.varname
+{
+    color: #004000;
+}
+
+span.command strong
+{
+    font-weight: normal;
+    color: #004000;
+}
+
+div.calloutlist table
+{
+    box-shadow: none;
+}
+
+table
+{
+    border-collapse: collapse;
+    box-shadow: 0.4em 0.4em 0.5em #e0e0e0;
+}
+
+table.simplelist
+{
+    text-align: left;
+    color: #005aa0;
+    border: 0;
+    padding: 5px;
+    background: #fffff5;
+    font-weight: normal;
+    font-style: italic;
+    box-shadow: none;
+    margin-bottom: 1em;
+}
+
+div.navheader table, div.navfooter table {
+    box-shadow: none;
+}
+
+div.affiliation
+{
+    font-style: italic;
+}

nix/overlay.nix

@@ -1,4 +1,5 @@
 self: super: {
   arion = super.callPackage ../arion.nix {};
   tests = super.callPackage ../tests {};
+  doc = super.callPackage ../doc {};
 }

src/nix/eval-service.nix

@@ -0,0 +1,25 @@
+{ lib, pkgs, ... }:
+
+{ modules, host }:
+let
+  composite = lib.evalModules {
+    check = true;
+    modules = builtinModules ++ modules;
+  };
+
+  builtinModules = [
+    argsModule
+    ./modules/service/docker-compose-service.nix
+    ./modules/service/host-store.nix
+    ./modules/service/host.nix
+  ];
+
+  argsModule = {
+    _file = ./docker-compose.nix;
+    key = ./docker-compose.nix;
+    config._module.args.pkgs = lib.mkForce pkgs;
+    config.host = host;
+  };
+
+in
+  composite

src/nix/modules/composition/docker-compose.nix

@@ -10,47 +10,28 @@
 
  */
 { pkgs, lib, config, ... }:
-
 let
-  evalService = name: modules:
+evalService = name: modules: (pkgs.callPackage ../../eval-service.nix {} { inherit modules; inherit (config) host; }).config.build.service;
-    let
-      composite = lib.evalModules {
-        check = true;
-        modules = builtinModules ++ modules;
-      };
-
-      builtinModules = [
-        argsModule
-        ../service/docker-compose-service.nix
-        ../service/host-store.nix
-        ../service/host.nix
-      ];
-
-      argsModule = {
-        _file = ./docker-compose.nix;
-        key = ./docker-compose.nix;
-        config._module.args.pkgs = lib.mkForce pkgs;
-        config.host = config.host;
-      };
-
-    in
-      composite.config.build.service;
 
 in
 {
   options = {
     build.dockerComposeYaml = lib.mkOption {
       type = lib.types.package;
+      description = "A derivation that produces a docker-compose.yaml file for this composition.";
     };
     build.dockerComposeYamlText = lib.mkOption {
       type = lib.types.string;
+      description = "The text of build.dockerComposeYaml.";
     };
     docker-compose.raw = lib.mkOption {
       type = lib.types.attrs;
+      description = "Nested attribute set that will be turned into the docker-compose.yaml file, using Nix's toJSON builtin.";
     };
     docker-compose.services = lib.mkOption {
       default = {};
       type = with lib.types; attrsOf (coercedTo unspecified (a: [a]) (listOf unspecified));
+      description = "A attribute set of service configurations. A service specifies how to run an image. Each of these service configurations is specified using modules whose options are described in the Service Options section.";
     };
   };
   config = {

src/nix/modules/composition/host-environment.nix

@@ -8,8 +8,9 @@
       description = ''
         The numeric user id (UID) of the user running arion.
 
-        Assuming this user id is helpful when dealing with the user's
+        This lets you to write modules that interact with the host
-        files, mounted into the container as a volume.
+        user's files, which is helpful for local development, but not
+        intended for production-like deployment scenarios.
       '';
     };
 

src/nix/modules/service/docker-compose-service.nix

@@ -9,79 +9,116 @@
 let
   inherit (lib) mkOption types;
   inherit (types) listOf nullOr attrsOf string either int bool;
+
+  dockerComposeRef = fragment:
+  ''See <link xlink:href="https://docs.docker.com/compose/compose-file/#${fragment}">Docker Compose#${fragment}</link>'';
+  dockerComposeKitchenSink = ''
+    Analogous to the <code>docker run</code> counterpart.
+
+    ${dockerComposeRef "domainname-hostname-ipc-mac_address-privileged-read_only-shm_size-stdin_open-tty-user-working_dir"}
+  '';
 in
 {
   options = {
     service.volumes = mkOption {
       type = listOf types.unspecified;
       default = [];
+      description = "";
     };
     service.build.context = mkOption {
       type = nullOr string;
       default = null;
+      description = ''
+        Locates a Dockerfile to use for creating an image to use in this service.
+
+        ${dockerComposeRef "context"}
+      '';
     };
     service.hostname = mkOption {
       type = nullOr string;
       default = null;
+      description = dockerComposeKitchenSink;
     };
     service.environment = mkOption {
       type = attrsOf (either string int);
       default = {};
+      description = dockerComposeRef "environment";
     };
     service.image = mkOption {
       type = string;
+      description = dockerComposeRef "image";
     };
     service.command = mkOption {
       type = nullOr types.unspecified;
       default = null;
+      description = dockerComposeRef "command";
     };
     service.depends_on = mkOption {
       type = listOf string;
       default = [];
+      description = dockerComposeRef "depends_on";
     };
     service.links = mkOption {
       type = listOf string;
       default = [];
+      description = dockerComposeRef "links";
     };
     service.external_links = mkOption {
       type = listOf string;
       default = [];
+      description = dockerComposeRef "external_links";
     };
     service.extra_hosts = mkOption {
       type = listOf string;
       default = [];
+      description = dockerComposeRef "extra_hosts";
     };
     service.working_dir = mkOption {
       type = nullOr string;
       default = null;
+      description = dockerComposeKitchenSink;
     };
     service.privileged = mkOption {
       type = nullOr bool;
       default = null;
+      description = dockerComposeKitchenSink;
     };
     service.entrypoint = mkOption {
       type = nullOr string;
       default = null;
+      description = dockerComposeRef "entrypoint";
     };
     service.restart = mkOption {
       type = nullOr string;
       default = null;
+      description = dockerComposeRef "restart";
     };
     service.ports = mkOption {
       type = listOf types.unspecified;
       default = [];
       description = ''
         Expose ports on host. "host:container" or structured.
-        See https://docs.docker.com/compose/compose-file/#ports
+
+        ${dockerComposeRef "ports"}
       '';
     };
     service.expose = mkOption {
       type = listOf string;
       default = [];
+      description = dockerComposeRef "expose";
     };
 
     build.service = mkOption {
       type = attrsOf types.unspecified;
+      description = ''
+        Raw input for the service in <code>docker-compose.yaml</code>.
+
+        You should not need to use this option. If anything is
+        missing, please contribute the missing option.
+
+        This option is user accessible because it may serve as an
+        escape hatch for some.
+      '';
     };
   };