Enable dune cache by default

bin/common.ml

@@ -583,6 +583,7 @@ module Builder = struct
     ; file_watcher : Dune_engine.Scheduler.Run.file_watcher
     ; workspace_config : Dune_rules.Workspace.Clflags.t
     ; cache_debug_flags : Dune_engine.Cache_debug_flags.t
+    ; cache_rules_default : bool
     ; report_errors_config : Dune_engine.Report_errors_config.t
     ; separate_error_messages : bool
     ; stop_on_first_error : bool
@@ -932,6 +933,20 @@ module Builder = struct
                useful for Dune developers to make Dune tests of the digest cache more \
                reproducible.")
     and+ cache_debug_flags = cache_debug_flags_term
+    and+ cache_rules_default =
+      let default =
+        Dune_lang.Toggle.of_bool !Dune_engine.Clflags.can_go_in_shared_cache_default
+      in
+      let doc =
+        Printf.sprintf
+          "Enable or disable caching rules (%s). Default is `%s'."
+          (Arg.doc_alts_enum Config.Toggle.all)
+          (Config.Toggle.to_string default)
+      in
+      Arg.(
+        value
+        & opt (enum Config.Toggle.all) default
+        & info [ "cache-rules" ] ~docs ~env:(Cmd.Env.info ~doc "DUNE_CACHE_RULES") ~doc)
     and+ report_errors_config =
       Arg.(
         value
@@ -1008,6 +1023,7 @@ module Builder = struct
         ; config_from_config_file
         }
     ; cache_debug_flags
+    ; cache_rules_default = Dune_lang.Toggle.enabled cache_rules_default
     ; report_errors_config
     ; separate_error_messages
     ; stop_on_first_error
@@ -1163,6 +1179,23 @@ let build (builder : Builder.t) =
   { builder; root; rpc; stats }
 ;;
 
+let maybe_init_cache (cache_config : Dune_cache.Config.t) =
+  match cache_config with
+  | Disabled -> cache_config
+  | Enabled _ ->
+    (match Dune_cache_storage.Layout.create_cache_directories () with
+     | Ok () -> cache_config
+     | Error (path, exn) ->
+       User_warning.emit
+         ~hints:
+           [ Pp.textf "Make sure the directory %s can be created" (Path.to_string path) ]
+         [ Pp.textf
+             "Cache directories could not be created: %s; disabling cache"
+             (Unix.error_message exn)
+         ];
+       Disabled)
+;;
+
 let init (builder : Builder.t) =
   let c = build builder in
   if c.root.dir <> Filename.current_dir_name then Sys.chdir c.root.dir;
@@ -1216,7 +1249,7 @@ let init (builder : Builder.t) =
   Dune_rules.Main.init
     ~stats:c.stats
     ~sandboxing_preference:config.sandboxing_preference
-    ~cache_config
+    ~cache_config:(maybe_init_cache cache_config)
     ~cache_debug_flags:c.builder.cache_debug_flags
     ();
   Only_packages.Clflags.set c.builder.only_packages;
@@ -1241,6 +1274,7 @@ let init (builder : Builder.t) =
   Dune_rules.Clflags.ignore_lock_dir := c.builder.ignore_lock_dir;
   Dune_rules.Clflags.on_missing_dune_project_file
   := if c.builder.require_dune_project_file then Error else Warn;
+  Dune_engine.Clflags.can_go_in_shared_cache_default := c.builder.cache_rules_default;
   Log.info
     [ Pp.textf
         "Workspace root: %s"

src/dune_cache_storage/layout.ml

@@ -82,7 +82,9 @@ let value_storage_dir = Versioned.value_storage_dir Version.Value.current
 let value_path = Versioned.value_path Version.Value.current
 
 let create_cache_directories () =
-  List.iter
-    [ temp_dir; metadata_storage_dir; file_storage_dir; value_storage_dir ]
-    ~f:(fun path -> ignore (Fpath.mkdir_p (Path.to_string path) : Fpath.mkdir_p_result))
+  [ temp_dir; metadata_storage_dir; file_storage_dir; value_storage_dir ]
+  |> Result.List.iter ~f:(fun path ->
+    match Fpath.mkdir_p (Path.to_string path) with
+    | Already_exists | Created -> Ok ()
+    | exception Unix.Unix_error (e, _, _) -> Error (path, e))
 ;;

src/dune_cache_storage/layout.mli

@@ -12,8 +12,11 @@ open Import
 val root_dir : Path.t
 
 (** Create a few subdirectories in [root_dir]. We expose this function because
-    we don't want to modify the file system when the cache is disabled. *)
-val create_cache_directories : unit -> unit
+    we don't want to modify the file system when the cache is disabled.
+
+    Returns whether creation has succeeded or in the case of error which directory
+    could not be created. *)
+val create_cache_directories : unit -> (unit, Path.t * Unix.error) result
 
 (** This directory stores metadata files, one per each historically executed
     build rule or output-producing action. (While this is a convenient mental

src/dune_config_file/dune_config_file.ml

@@ -289,9 +289,9 @@ module Dune_config = struct
     ; concurrency = (if Execution_env.inside_dune then Fixed 1 else Auto)
     ; terminal_persistence = Clear_on_rebuild
     ; sandboxing_preference = []
-    ; cache_enabled = `Disabled
+    ; cache_enabled = `Enabled
     ; cache_reproducibility_check = Skip
-    ; cache_storage_mode = None
+    ; cache_storage_mode = Some (Dune_cache_storage.Mode.default ())
     ; action_stdout_on_success = Print
     ; action_stderr_on_success = Print
     ; experimental = []

src/dune_engine/action.ml

@@ -336,7 +336,7 @@ module Full = struct
   let make
     ?(env = Env.empty)
     ?(locks = [])
-    ?(can_go_in_shared_cache = true)
+    ?(can_go_in_shared_cache = !Clflags.can_go_in_shared_cache_default)
     ?(sandbox = Sandbox_config.default)
     action
     =

src/dune_engine/action.mli

@@ -152,7 +152,8 @@ module Full : sig
   val make
     :  ?env:Env.t (** default [Env.empty] *)
     -> ?locks:Path.t list (** default [[]] *)
-    -> ?can_go_in_shared_cache:bool (** default [true] *)
+    -> ?can_go_in_shared_cache:bool
+         (** default [!Clflags.can_fo_in_shared_cache_default] *)
     -> ?sandbox:Sandbox_config.t (** default [Sandbox_config.default] *)
     -> action
     -> t

src/dune_engine/build_config.ml

@@ -106,11 +106,6 @@ let set
         contexts
         ~f:(fun ((ctx : Build_context.t), ctx_type) -> ctx.name, (ctx, ctx_type)))
   in
-  let () =
-    match (cache_config : Dune_cache.Config.t) with
-    | Disabled -> ()
-    | Enabled _ -> Dune_cache_storage.Layout.create_cache_directories ()
-  in
   Fdecl.set
     t
     { contexts

src/dune_engine/clflags.ml

@@ -19,3 +19,4 @@ let promote = ref None
 let force = ref false
 let always_show_command_line = ref false
 let display = ref Display.Quiet
+let can_go_in_shared_cache_default = ref false

src/dune_engine/clflags.mli

@@ -34,3 +34,6 @@ val always_show_command_line : bool ref
 
 (** The display mode *)
 val display : Display.t ref
+
+(** Whether actions are cacheable by default, default [false] *)
+val can_go_in_shared_cache_default : bool ref

src/dune_rules/dune

@@ -33,6 +33,7 @@
   build_path_prefix_map
   dune_engine
   dune_vcs
+  dune_cache_storage
   dune_config
   dune_config_file
   dune_findlib

src/dune_rules/simple_rules.ml

@@ -63,7 +63,7 @@ let add_user_rule
   sctx
   ~dir
   ~(rule : Rule_conf.t)
-  ~(action : _ Action_builder.With_targets.t)
+  ~(action : Action.Full.t Action_builder.With_targets.t)
   ~expander
   =
   let action =

test/blackbox-tests/test-cases/default-cache.t

@@ -0,0 +1,35 @@
+The dune cache should be enabled by default
+
+  $ echo "(lang dune 3.17)" > dune-project
+
+  $ cat > dune << EOF
+  > (library
+  >  (name foo))
+  > EOF
+
+  $ cat > foo.ml << EOF
+  > let f x y = x + y
+  > EOF
+
+Set up cache directory
+
+  $ export DUNE_CACHE_ROOT=$(pwd)/dune_test_cache
+  $ mkdir $DUNE_CACHE_ROOT
+  $ DUNE_CACHE=disabled dune build
+  $ ls $DUNE_CACHE_ROOT
+
+We have not written anything to the cache yet.
+
+Change source files to force a recompilation
+
+  $ cat > foo.ml << EOF
+  > let f x y = x - y
+  > EOF
+  $ dune build
+  $ ls $DUNE_CACHE_ROOT | sort
+  files
+  meta
+  temp
+  values
+
+Cache has been written to!

test/blackbox-tests/test-cases/directory-targets/cache-file-and-dir.t

@@ -2,6 +2,7 @@ This checks what happens when a file available in the cache is used in a directo
 
   $ export DUNE_CACHE_ROOT=$PWD/.cache
   $ export DUNE_CACHE=enabled
+  $ export DUNE_CACHE_RULES=enabled
   $ . ./helpers.sh
 
   $ cat > dune-project << EOF

test/blackbox-tests/test-cases/directory-targets/cache-shared-subdir.t

@@ -1,6 +1,7 @@
 We create 2 directory targets which share a whole subdirectory.
 
   $ export DUNE_CACHE_ROOT=$PWD/.cache
+  $ export DUNE_CACHE_RULES=enabled
   $ export DUNE_CACHE=enabled
   $ . ./helpers.sh
 

test/blackbox-tests/test-cases/directory-targets/cache.t

@@ -1,6 +1,7 @@
 We test that directory targets can go in the shared cache. See #8067.
 
   $ export DUNE_CACHE_ROOT=$PWD/.cache
+  $ export DUNE_CACHE_RULES=enabled
   $ export DUNE_CACHE=enabled
 
 In project a, we create a rule with a directory target. The script that creates

test/blackbox-tests/test-cases/dune-cache/config.t

@@ -26,6 +26,7 @@ Check that old cache configuration format works fine with an old language
 Test that DUNE_CACHE_ROOT can be used to control the cache location
 
   $ export DUNE_CACHE_ROOT=$PWD/.cache
+  $ export DUNE_CACHE_RULES=enabled
 
 Build succeeds and the 'copy' mode is respected
 

test/blackbox-tests/test-cases/dune-cache/dedup.t

@@ -2,6 +2,7 @@ Test deduplication of build artifacts when using Dune cache with hard links.
 
   $ export DUNE_CACHE=enabled
   $ export DUNE_CACHE_ROOT=$PWD/.cache
+  $ export DUNE_CACHE_RULES=enabled
 
   $ cat > dune-project <<EOF
   > (lang dune 2.1)

test/blackbox-tests/test-cases/dune-cache/missing-cache-entries.t

@@ -1,6 +1,7 @@
 Check that Dune cache can cope with missing file/metadata entries.
 
   $ export DUNE_CACHE_ROOT=$PWD/.cache
+  $ export DUNE_CACHE_RULES=enabled
 
   $ cat > config <<EOF
   > (lang dune 2.1)

test/blackbox-tests/test-cases/dune-cache/mode-copy.t

@@ -5,6 +5,7 @@ variable, and via the [DUNE_CACHE_ROOT] variable. Here we test the former.
 
   $ export XDG_RUNTIME_DIR=$PWD/.xdg-runtime
   $ export XDG_CACHE_HOME=$PWD/.xdg-cache
+  $ export DUNE_CACHE_RULES=enabled
 
   $ cat > config <<EOF
   > (lang dune 3.0)

test/blackbox-tests/test-cases/dune-cache/mode-hardlink.t

@@ -5,6 +5,7 @@ variable, and via the [DUNE_CACHE_ROOT] variable. Here we test the former.
 
   $ export XDG_RUNTIME_DIR=$PWD/.xdg-runtime
   $ export XDG_CACHE_HOME=$PWD/.xdg-cache
+  $ export DUNE_CACHE_RULES=enabled
 
   $ cat > config <<EOF
   > (lang dune 2.1)

test/blackbox-tests/test-cases/dune-cache/readonly-fs.t

@@ -17,16 +17,24 @@ where Dune is supposed to store the cache:
   $ export DUNE_CACHE_ROOT=$(pwd)/readonly/cache-dir
 
   $ dune build
-  Error:
-  mkdir($TESTCASE_ROOT/readonly/cache-dir): Permission denied
-  [1]
+  Warning: Cache directories could not be created: Permission denied; disabling
+  cache
+  Hint: Make sure the directory
+  $TESTCASE_ROOT/readonly/cache-dir/temp
+  can be created
 
 Likewise, this should also happen if the location is set via XDG variables.
 
   $ unset DUNE_CACHE_ROOT
   $ export XDG_CACHE_HOME=$(pwd)/readonly/xdg-cache-dir
+  $ export DUNE_CONFIG__SKIP_LINE_BREAK=enabled
 
-  $ dune build
-  Error:
-  mkdir($TESTCASE_ROOT/readonly/xdg-cache-dir): Permission denied
-  [1]
+  $ dune build 2>&1 | sed 's/created: .*;/created: $REASON:/'
+  Warning: Cache directories could not be created: $REASON: disabling cache
+  Hint: Make sure the directory $TESTCASE_ROOT/readonly/xdg-cache-dir/dune/db/temp can be created
+
+  $ HOME=/homeless-shelter
+  $ unset XDG_CACHE_HOME
+  $ dune build 2>&1 | sed 's/created: .*;/created: $REASON:/'
+  Warning: Cache directories could not be created: $REASON: disabling cache
+  Hint: Make sure the directory /homeless-shelter/.cache/dune/db/temp can be created

test/blackbox-tests/test-cases/dune-cache/repro-check.t

@@ -1,6 +1,7 @@
 Test reproducibility check
 
   $ export DUNE_CACHE_ROOT=$PWD/.cache
+  $ export DUNE_CACHE_RULES=enabled
   $ cat > config <<EOF
   > (lang dune 3.0)
   > (cache enabled)

test/blackbox-tests/test-cases/dune-cache/size.t/run.t

@@ -3,6 +3,7 @@ the cache.
 
   $ export DUNE_CACHE=enabled
   $ export DUNE_CACHE_ROOT=$PWD/.cache
+  $ export DUNE_CACHE_RULES=enabled
 
   $ cat > config << EOF
   > (lang dune 3.7)

test/blackbox-tests/test-cases/dune-cache/symlink.t

@@ -3,6 +3,7 @@ produced symbolic links work correctly and are appropriately cached.
 
   $ export DUNE_CACHE=enabled
   $ export DUNE_CACHE_ROOT=$PWD/.cache
+  $ export DUNE_CACHE_RULES=enabled
 
   $ cat > dune-project <<EOF
   > (lang dune 2.1)

test/blackbox-tests/test-cases/dune-cache/trim.t

@@ -1,4 +1,5 @@
   $ export DUNE_CACHE=enabled
+  $ export DUNE_CACHE_RULES=enabled
   $ export XDG_RUNTIME_DIR=$PWD/.xdg-runtime
   $ export XDG_CACHE_HOME=$PWD/.xdg-cache
 

test/blackbox-tests/test-cases/pkg/toolchain-installation.t

@@ -85,9 +85,7 @@ but the fake compiler will end up installed as a toolchain package.
   Unrecognized line: "Hello from fake ocamlc!"
 
 Enumerate the contents of the fake toolchains directory:
-  $ find fake-cache | sort | remove_hash
-  fake-cache
-  fake-cache/dune
+  $ find fake-cache/dune/toolchains | sort | remove_hash
   fake-cache/dune/toolchains
   fake-cache/dune/toolchains/ocaml-base-compiler.1-HASH
   fake-cache/dune/toolchains/ocaml-base-compiler.1-HASH/target

test/expect-tests/dune_config_file/dune_config_test.ml

@@ -22,9 +22,9 @@ let%expect_test "cache-check-probability 0.1" =
     ; concurrency = Fixed 1
     ; terminal_persistence = Clear_on_rebuild
     ; sandboxing_preference = []
-    ; cache_enabled = Disabled
+    ; cache_enabled = Enabled
     ; cache_reproducibility_check = Check_with_probability 0.1
-    ; cache_storage_mode = None
+    ; cache_storage_mode = Some Hardlink
     ; action_stdout_on_success = Print
     ; action_stderr_on_success = Print
     ; experimental = []
@@ -40,7 +40,7 @@ let%expect_test "cache-storage-mode copy" =
     ; concurrency = Fixed 1
     ; terminal_persistence = Clear_on_rebuild
     ; sandboxing_preference = []
-    ; cache_enabled = Disabled
+    ; cache_enabled = Enabled
     ; cache_reproducibility_check = Skip
     ; cache_storage_mode = Some Copy
     ; action_stdout_on_success = Print
@@ -58,7 +58,7 @@ let%expect_test "cache-storage-mode hardlink" =
     ; concurrency = Fixed 1
     ; terminal_persistence = Clear_on_rebuild
     ; sandboxing_preference = []
-    ; cache_enabled = Disabled
+    ; cache_enabled = Enabled
     ; cache_reproducibility_check = Skip
     ; cache_storage_mode = Some Hardlink
     ; action_stdout_on_success = Print