Add 'nix doc' command

This command generates HTML docs (using mdbook) for a flake.

corepkgs/module.nix

@@ -12,14 +12,14 @@ let
 
 in
 
-{ description ? null, extends ? [], options ? {}, config ? ({ config }: {}) } @ inArgs:
+{ doc ? null, extends ? [], options ? {}, config ? ({ config }: {}) } @ inArgs:
 
 let thisModule = rec {
   type = "module";
 
   _module = {
-    inherit description extends options config;
-  };
+    inherit extends options config;
+  } // (if doc != null then { inherit doc; } else {});
 
   _allModules = [thisModule] ++ builtins.concatLists (map (mod: assert mod.type or "<untyped>" == "module"; mod._allModules) extends);
 

src/nix/bundle.cc

@@ -98,14 +98,14 @@ struct CmdBundle : InstallableCommand
         if (!evalState->isDerivation(*vRes))
             throw Error("the bundler '%s' does not produce a derivation", bundler.what());
 
-        auto attr1 = vRes->attrs->find(evalState->sDrvPath);
+        auto attr1 = vRes->attrs->get(evalState->sDrvPath);
         if (!attr1)
             throw Error("the bundler '%s' does not produce a derivation", bundler.what());
 
         PathSet context2;
         StorePath drvPath = store->parseStorePath(evalState->coerceToPath(*attr1->pos, *attr1->value, context2));
 
-        auto attr2 = vRes->attrs->find(evalState->sOutPath);
+        auto attr2 = vRes->attrs->get(evalState->sOutPath);
         if (!attr2)
             throw Error("the bundler '%s' does not produce a derivation", bundler.what());
 

src/nix/command.hh

@@ -58,6 +58,23 @@ struct MixFlakeOptions : virtual Args, EvalCommand
     { return {}; }
 };
 
+class FlakeCommand : virtual Args, public MixFlakeOptions
+{
+    std::string flakeUrl = ".";
+
+public:
+
+    FlakeCommand();
+
+    FlakeRef getFlakeRef();
+
+    flake::Flake getFlake();
+
+    flake::LockedFlake lockFlake();
+
+    std::optional<FlakeRef> getFlakeRefForCompletion() override;
+};
+
 /* How to handle derivations in commands that operate on store paths. */
 enum class OperateOn {
     /* Operate on the output path. */

src/nix/doc.cc

@@ -0,0 +1,101 @@
+#include "command.hh"
+#include "common-args.hh"
+#include "eval-cache.hh"
+#include "eval-inline.hh"
+
+using namespace nix;
+using namespace nix::flake;
+
+// FIXME: move
+StorePath buildDerivation(EvalState & state, Value & vDerivation)
+{
+    state.forceValue(vDerivation);
+    if (!state.isDerivation(vDerivation))
+        throw Error("value did not evaluate to a derivation");
+
+    auto aDrvPath = vDerivation.attrs->get(state.sDrvPath);
+    assert(aDrvPath);
+    PathSet context;
+    auto drvPath = state.store->parseStorePath(state.coerceToPath(*aDrvPath->pos, *aDrvPath->value, context));
+
+    state.store->buildPaths({{drvPath}});
+
+    auto aOutPath = vDerivation.attrs->get(state.sOutPath);
+    assert(aOutPath);
+    auto outPath = state.store->parseStorePath(state.coerceToPath(*aOutPath->pos, *aOutPath->value, context));
+
+    assert(state.store->isValidPath(outPath));
+
+    return outPath;
+}
+
+struct CmdDoc : FlakeCommand
+{
+    std::optional<Path> outLink = "flake-doc";
+    bool printMarkdown = false;
+
+    CmdDoc()
+    {
+        // FIXME: cut&paste from 'nix build'.
+        addFlag({
+            .longName = "out-link",
+            .shortName = 'o',
+            .description = "path of the symlink to the build result",
+            .labels = {"path"},
+            .handler = {&outLink},
+            .completer = completePath
+        });
+
+        addFlag({
+            .longName = "no-link",
+            .description = "do not create a symlink to the build result",
+            .handler = {&outLink, {}},
+        });
+
+        addFlag({
+            .longName = "print-markdown",
+            .description = "show markdown, don't generate an HTML book",
+            .handler = {&this->printMarkdown, true},
+        });
+    }
+
+    void run(nix::ref<nix::Store> store) override
+    {
+        auto state = getEvalState();
+        auto flake = std::make_shared<LockedFlake>(lockFlake());
+
+        auto vFlake = state->allocValue();
+        flake::callFlake(*state, *flake, *vFlake);
+
+        auto vFun = state->allocValue();
+        state->eval(state->parseExprFromString(
+            #include "doc.nix.gen.hh"
+            , "/"), *vFun);
+
+        auto vRes = state->allocValue();
+        state->callFunction(*vFun, *vFlake, *vRes, noPos);
+        state->forceAttrs(*vRes, noPos);
+
+        auto markdown = vRes->attrs->get(state->symbols.create("markdown"));
+        assert(markdown);
+
+        if (printMarkdown) {
+            logger->stdout(state->forceString(*markdown->value));
+            return;
+        }
+
+        auto mdbook = vRes->attrs->get(state->symbols.create("mdbook"));
+        assert(mdbook);
+
+        // FIXME: ugly, needed for getFlake.
+        evalSettings.pureEval = false;
+
+        auto path = buildDerivation(*state, *mdbook->value);
+
+        if (outLink)
+            if (auto store2 = store.dynamic_pointer_cast<LocalFSStore>())
+                store2->addPermRoot(path, absPath(*outLink));
+    }
+};
+
+static auto r1 = registerCommand<CmdDoc>("doc");

src/nix/doc.nix

@@ -0,0 +1,94 @@
+with builtins;
+
+flake:
+
+let
+
+  splitLines = s: filter (x: !isList x) (split "\n" s);
+
+  concatStrings = concatStringsSep "";
+
+  modules = flake.modules or {};
+
+in
+
+rec {
+  markdown =
+    # FIXME: split into multiple files.
+
+    "# Outputs\n\n"
+
+    + concatStrings (map
+      (outputName:
+        "  - `${outputName}`  \n\n")
+      (attrNames flake.outputs))
+
+    + (if modules != {} then
+      "# Modules\n\n"
+      + concatStrings (map
+        (moduleName:
+          let
+            module = modules.${moduleName};
+          in
+          "## `${moduleName}`\n\n"
+          + (if module._module.doc or "" != ""
+             then "### Synopsis\n\n${module._module.doc}\n\n"
+             else "")
+          + (if module._module.options != {}
+             then
+               "### Options\n\n"
+               + concatStrings (map
+                 (optionName:
+                   let option = module._module.options.${optionName}; in
+                   "  - `${optionName}`  \n\n"
+                   + concatStrings (map (l: "    ${l}\n") (splitLines option.doc))
+                   + "\n"
+                 )
+                 (attrNames module._module.options))
+             else "")
+        )
+        (attrNames modules))
+       else "");
+
+  mdbook =
+    let
+      nixpkgs = getFlake "nixpkgs";
+      pkgs = nixpkgs.legacyPackages.x86_64-linux; # FIXME
+    in
+      pkgs.runCommand "flake-doc"
+        { buildInputs = [ pkgs.mdbook ];
+        }
+        ''
+          mkdir $out
+          mkdir -p book/src
+
+          cat > book/book.toml <<EOF
+          [output.html]
+          additional-css = ["custom.css"]
+          EOF
+
+          cat > book/custom.css <<EOF
+          h1:not(:first-of-type) {
+              margin-top: 1.3em;
+          }
+
+          h2 {
+              margin-top: 1em;
+          }
+
+          h3 {
+              margin-top: 0.7em;
+          }
+          EOF
+
+          cat > book/src/SUMMARY.md <<EOF
+          # Table of Contents
+
+          - [Overview](overview.md)
+          EOF
+
+          cp ${toFile "flake.md" markdown} book/src/overview.md
+
+          mdbook build -d $out book
+        '';
+}

src/nix/flake.cc

@@ -20,13 +20,7 @@
 using namespace nix;
 using namespace nix::flake;
 
-class FlakeCommand : virtual Args, public MixFlakeOptions
-{
-    std::string flakeUrl = ".";
-
-public:
-
-    FlakeCommand()
+FlakeCommand::FlakeCommand()
 {
     expectArgs({
         .label = "flake-url",
@@ -38,27 +32,26 @@ public:
     });
 }
 
-    FlakeRef getFlakeRef()
+FlakeRef FlakeCommand::getFlakeRef()
 {
     return parseFlakeRef(flakeUrl, absPath(".")); //FIXME
 }
 
-    Flake getFlake()
+Flake FlakeCommand::getFlake()
 {
     auto evalState = getEvalState();
     return flake::getFlake(*evalState, getFlakeRef(), lockFlags.useRegistries);
 }
 
-    LockedFlake lockFlake()
+LockedFlake FlakeCommand::lockFlake()
 {
     return flake::lockFlake(*getEvalState(), getFlakeRef(), lockFlags);
 }
 
-    std::optional<FlakeRef> getFlakeRefForCompletion() override
+std::optional<FlakeRef> FlakeCommand::getFlakeRefForCompletion()
 {
     return getFlakeRef();
 }
-};
 
 static void printFlakeInfo(const Store & store, const Flake & flake)
 {

src/nix/local.mk

@@ -31,3 +31,5 @@ src/nix-env/user-env.cc: src/nix-env/buildenv.nix.gen.hh
 src/nix/develop.cc: src/nix/get-env.sh.gen.hh
 
 src/nix-channel/nix-channel.cc: src/nix-channel/unpack-channel.nix.gen.hh
+
+src/nix/doc.cc: src/nix/doc.nix.gen.hh

src/nix/options.cc

@@ -45,12 +45,12 @@ struct CmdListOptions : InstallableCommand
 
             state->forceAttrs(*option->value);
 
-            std::string description = ANSI_ITALIC "<no description>" ANSI_NORMAL;
-            auto aDescription = option->value->attrs->get(state->symbols.create("description"));
-            if (aDescription)
+            std::string doc = ANSI_ITALIC "<no description>" ANSI_NORMAL;
+            auto aDoc = option->value->attrs->get(state->symbols.create("doc"));
+            if (aDoc)
                 // FIXME: render markdown.
-                description = state->forceString(*aDescription->value);
-            logger->stdout("  " ANSI_BOLD "Description:" ANSI_NORMAL " %s", description);
+                doc = state->forceString(*aDoc->value);
+            logger->stdout("  " ANSI_BOLD "Description:" ANSI_NORMAL " %s", doc);
 
             auto aValue = aFinal->value->attrs->get(option->name);
             assert(aValue);