feat: Always document the transitive closure of a module

README.md

@@ -14,12 +14,17 @@ Then update your dependencies:
 lake -Kenv=dev update
 ```
 
-Then you can generate documentation for an entire library using:
+Then you can generate documentation for an entire library and all files imported
+by that library using:
 ```
 lake -Kenv=dev build Test:docs
 ```
-If you have multiple libraries you want to generate documentation for
-the recommended way right now is to run it for each library.
+If you have multiple libraries you want to generate full documentation for:
+```
+lake -Kenv=dev build Test:docs Foo:docs
+```
+Note that doc-gen currently always generates documentation for `Lean`, `Init`
+and `Lake` in addition to the provided targets.
 
 ## Development of doc-gen4
 You can build docs using a modified `doc-gen4` as follows:  Replace the `from git  "..." @ "main"` in the `lakefile.lean` with just `from "..."` using the path to the modified version of `doc-gen4`.  E.g. if the
@@ -31,10 +36,10 @@ require «doc-gen4» from "../doc-gen4"
 
 The root of the built docs will be `build/docs/index.html`.  However, due to the "Same Origin Policy", the
 generated website will be partially broken if you just open the generated html files in your browser.  You
-need to serve them from a proper http server for it to work.  An easy way to do that is to run 
+need to serve them from a proper http server for it to work.  An easy way to do that is to run
 `python3 -m http.server` from the `build/docs` directory.
 
-Note that if you modify the `.js` or `.css` files in doc-gen4, they won't necessarily be copied over when 
+Note that if you modify the `.js` or `.css` files in doc-gen4, they won't necessarily be copied over when
 you rebuild the documentation.  You can manually copy the changes to the `build/docs` directory to make
 sure the changes appear, or just do a full recompilation (`lake clean` and `lake build` inside the `doc-gen4`
 directory.)

lakefile.lean

@@ -29,6 +29,9 @@ module_facet docs (mod) : FilePath := do
   let exeJob ← docGen4.exe.fetch
   let modJob ← mod.leanArts.fetch
   let buildDir := (← getWorkspace).root.buildDir
+  -- Build all documentation imported modules
+  let imports ← mod.imports.fetch
+  imports.forM fun mod => discard <| fetch <| mod.facet `docs
   let docFile := mod.filePath (buildDir / "doc") "html"
   exeJob.bindAsync fun exeFile exeTrace => do
   modJob.bindSync fun _ modTrace => do