feat: lake exe mk_all as a Lean executable (#11853)

Running
```bash
lake exe mk_all --git
```
should have the same effect as running
```bash
./script/mk_all.sh
```

that is, it creates the files `Mathlib.lean`, `Mathlib/Tactic.lean`, `Archive.lean`, `Counterexamples.lean`.

It does *not* create analogous files for `Cache` and `LongestPole`.

```bash
lake exe mk_all
```
is similar, but uses all the `.lean` files in `Mathlib`, not just the Git-managed ones.

See #11874 for using the script in CI.



Co-authored-by: Yaël Dillies <yael.dillies@gmail.com>

lakefile.lean

@@ -56,6 +56,11 @@ lean_exe checkYaml where
   srcDir := "scripts"
   supportInterpreter := true
 
+/-- `lake exe mk_all` constructs the files containing all imports for a project. -/
+lean_exe mk_all where
+  srcDir := "scripts"
+  supportInterpreter := true
+
 /-- `lake exe shake` checks files for unnecessary imports. -/
 lean_exe shake where
   root := `Shake.Main

scripts/mk_all.lean

@@ -0,0 +1,113 @@
+/-
+Copyright (c) 2024 Yaël Dillies, Damiano Testa. All rights reserved.
+Released under Apache 2.0 license as described in the file LICENSE.
+Authors: Yaël Dillies, Damiano Testa
+-/
+import Cli.Basic
+import Lean.Util.Path
+import Lake.CLI.Main
+
+/-!
+# Script to create a file importing all files from a folder
+
+This file declares a command to gather all Lean files from a folder into a single Lean file.
+
+TODO:
+`getLeanLibs` contains a hard-coded choice of which dependencies should be built and which ones
+should not.  Could this be made more structural and robust, possibly with extra `Lake` support?
+-/
+
+open Lean System.FilePath
+
+/-- `getAll git ml` takes all `.lean` files in the dir `ml` (recursing into sub-dirs) and
+returns the `Array` of `String`s
+```
+#[file₁, ..., fileₙ]
+```
+where each `fileᵢ` is of the form `"Mathlib.Algebra.Algebra.Basic"`.
+
+The input `git` is a `Bool`ean flag:
+* `true` means that the command uses `git ls-files` to find the relevant files;
+* `false` means that the command recursively scans all dirs searching for `.lean` files.
+-/
+def getAll (git : Bool) (ml : String) : IO (Array String) := do
+  let ml.lean := addExtension ⟨ml⟩ "lean"  -- for example, `Mathlib.lean`
+  let allModules : Array System.FilePath ← (do
+    if git then
+      let mlDir := ml.push pathSeparator   -- for example, `Mathlib/`
+      let allLean ← IO.Process.run { cmd := "git", args := #["ls-files", mlDir ++ "*.lean"] }
+      return (((allLean.dropRightWhile (· == '\n')).splitOn "\n").map (⟨·⟩)).toArray
+    else do
+      let all ← walkDir ml
+      return all.filter (·.extension == some "lean"))
+  let files := (allModules.erase ml.lean).qsort (·.toString < ·.toString)
+  let withImport ← files.mapM fun f => do
+    -- this check is helpful in case the `git` option is on and a local file has been removed
+    if ← pathExists f then
+      return (← moduleNameOfFileName f none).toString
+    else return ""
+  return withImport.filter (· != "")
+
+open Lake in
+/-- `getLeanLibs` returns the names (as an `Array` of `String`s) of all the libraries
+on which the current project depends.
+If the current project is `mathlib`, then it excludes the libraries `Cache` and `LongestPole` and
+it includes `Mathlib/Tactic`. -/
+def getLeanLibs : IO (Array String) := do
+  let (elanInstall?, leanInstall?, lakeInstall?) ← findInstall?
+  let config ← MonadError.runEIO <| mkLoadConfig { elanInstall?, leanInstall?, lakeInstall? }
+  let ws ← MonadError.runEIO (MainM.runLogIO (loadWorkspace config)).toEIO
+  let package := ws.root
+  let libs := (package.leanLibs.map (·.name)).map (·.toString)
+  return if package.name == `mathlib then
+    libs.erase "Cache" |>.erase "LongestPole" |>.push ("Mathlib".push pathSeparator ++ "Tactic")
+  else
+    libs
+
+open IO.FS IO.Process Name Cli in
+/-- Implementation of the `mk_all` command line program.
+The exit code is the number of files that the command updates/creates. -/
+def mkAllCLI (args : Parsed) : IO UInt32 := do
+  -- Check whether the `--git` flag was set
+  let git := (args.flag? "git").isSome
+  -- Check whether the `--lib` flag was set. If so, build the file corresponding to the library
+  -- passed to `--lib`. Else build all the libraries of the package.
+  -- If the package is `mathlib`, then it removes the libraries `Cache` and `LongestPole` and it
+  -- adds `Mathlib/Tactic`.
+  let libs := ← match args.flag? "lib" with
+              | some lib => return #[lib.as! String]
+              | none => getLeanLibs
+  let mut updates := 0
+  for d in libs.reverse do  -- reverse to create `Mathlib/Tactic.lean` before `Mathlib.lean`
+    let fileName := addExtension d "lean"
+    let allFiles ← getAll git d
+    let fileContent := ("\n".intercalate (allFiles.map ("import " ++ ·)).toList).push '\n'
+    if !(← pathExists fileName) then
+      IO.println s!"Creating '{fileName}'"
+      updates := updates + 1
+      IO.FS.writeFile fileName fileContent
+    else if (← IO.FS.readFile fileName) != fileContent then
+      IO.println s!"Updating '{fileName}'"
+      updates := updates + 1
+      IO.FS.writeFile fileName fileContent
+  if updates == 0 then
+    IO.println "No update necessary"
+  return updates
+
+open Cli in
+/-- Setting up command line options and help text for `lake exe mk_all`. -/
+def mkAll : Cmd := `[Cli|
+  mk_all VIA mkAllCLI; ["0.0.1"]
+  "Generate a file importing all the files of a Lean folder. \
+   By default, it generates the files for the Lean libraries of the package.\
+   In the case of `Mathlib`, it removes the libraries `Cache` and `LongestPole`\
+   and it adds `Mathlib/Tactic`. \
+   If you are working in a project downstream of mathlib, use `lake exe mk_all --lib MyProject`."
+
+  FLAGS:
+    lib : String; "Create a folder importing all Lean files from the specified library/subfolder."
+    git;          "Use the folder content information from git."
+]
+
+/-- The entrypoint to the `lake exe mk_all` command. -/
+def main (args : List String) : IO UInt32 := mkAll.validate args