Use builtins.traceVerbose for logging (#216)

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 - #210: Add `extraLibraries` to `settings` module.
 - #215: Improved debug logging.
+- #216: Remove `debug` option (pass `--trace-verbose` to nix instead)
 
 ## 0.4.0 (Aug 22, 2023)
 

doc/guide/debugging.md

@@ -4,23 +4,20 @@ slug: /haskell-flake/debugging
 
 # Debugging logs
 
-Enabling the `debug` option causes haskell-flake to print verbose logging of its activity. To enable it:
-
-```nix
-haskellProjects.default = {
-  debug = true;  # Turn on verbose logging
-  projectRoot = ./.;
-  ...
-}
-```
+:::warning
+This feature is available only in Nix versions 2.10 or later.
+:::
+
+Passing `--trace-verbose` to Nix commands causes haskell-flake to print verbose logging of its activity. To enable it:
 
->[!tip] Timestamps in logs
-> `moreutils` provides the `ts` command that you can pipe your nix command output to in order to get timestamps in the logs.
+:::tip[Timestamps in logs]
+`moreutils` provides the `ts` command that you can pipe your nix command output to in order to get timestamps in the logs.
+:::
 
-With debug option enabled, you can execute your `nix` commands piped through `ts` to get timestamps in the debug logs. The below is a sample output when building [haskell-multi-nix](https://github.com/srid/haskell-multi-nix/tree/debug):
+The below is a sample output when building [haskell-multi-nix](https://github.com/srid/haskell-multi-nix/tree/debug) with `--trace-verbose`:
 
 ```
-$ nix build github:srid/haskell-multi-nix/debug#bar 2>&1 | ts '[%Y-%m-%d %H:%M:%S]'
+$ nix build --trace-verbose github:srid/haskell-multi-nix#bar 2>&1 | ts '[%Y-%m-%d %H:%M:%S]'
 [2024-01-11 15:33:32] trace: DEBUG[haskell-flake] [k0ad89r6pa70rly68ibff1jkw59bljgh-source#haskellProjects.default]: default.findPackagesInCabalProject = {"bar":"/nix/store/k0ad89r6pa70rly68ibff1jkw59bljgh-source/./bar","foo":"/nix/store/k0ad89r6pa70rly68ibff1jkw59bljgh-source/./foo"}
 [2024-01-11 15:33:32] trace: DEBUG[haskell-flake] [k0ad89r6pa70rly68ibff1jkw59bljgh-source#haskellProjects.default]: defaults.packages = {"bar":{"imports":[{"_file":"/nix/store/n2nb5achv6p0bv3nvqw731mfr907d8ny-source/nix/modules/project/defaults.nix, via option perSystem.aarch64-darwin.haskellProjects.default.defaults.packages.bar","imports":[{"source":"/nix/store/k0ad89r6pa70rly68ibff1jkw59bljgh-source/./bar"}]}]},"foo":{"imports":[{"_file":"/nix/store/n2nb5achv6p0bv3nvqw731mfr907d8ny-source/nix/modules/project/defaults.nix, via option perSystem.aarch64-darwin.haskellProjects.default.defaults.packages.foo","imports":[{"source":"/nix/store/k0ad89r6pa70rly68ibff1jkw59bljgh-source/./foo"}]}]}}
 [2024-01-11 15:33:32] trace: DEBUG[haskell-flake] [k0ad89r6pa70rly68ibff1jkw59bljgh-source#haskellProjects.default]: bar.getCabalExecutables = bar
@@ -36,4 +33,8 @@ $ nix build github:srid/haskell-multi-nix/debug#bar 2>&1 | ts '[%Y-%m-%d %H:%M:%
 [2024-01-11 15:33:35] trace: DEBUG[haskell-flake] [k0ad89r6pa70rly68ibff1jkw59bljgh-source#haskellProjects.default]: foo.cabal2nixDeriver /nix/store/i36x01zcdpm7c3m3fjjq1qa4slv61jpw-cabal2nix-foo
 [2024-01-11 15:33:35] trace: DEBUG[haskell-flake] [k0ad89r6pa70rly68ibff1jkw59bljgh-source#haskellProjects.default]: foo.fromSdist /nix/store/qrsy0bm4khcs1hxy0rhb6m3g2bvi15sm-foo-0.1.0.0
 [2024-01-11 15:33:35] trace: DEBUG[haskell-flake] [k0ad89r6pa70rly68ibff1jkw59bljgh-source#haskellProjects.default]: bar.fromSdist /nix/store/anyx51rm5gjdclafcz5is7jpqgfq2i4w-bar-0.1.0.0
-```
+```
+
+## See also
+
+- Read more about [the `traceVerbose` function](https://nixos.asia/en/traceVerbose) which haskell-flake uses to produce the above logs.

nix/logging.nix

@@ -1,11 +1,11 @@
-{ name, debug ? false, ... }:
+{ name, ... }:
 
 {
-  traceDebug = msg:
-    if debug then
-      builtins.trace ("DEBUG[haskell-flake] [${name}]: " + msg)
-    else
-      x: x;
+  # traceDebug uses traceVerbose; and is no-op on Nix versions below 2.10
+  traceDebug =
+    if builtins.compareVersions "2.10" builtins.nixVersion < 0
+    then msg: builtins.traceVerbose ("DEBUG[haskell-flake] [${name}]: " + msg)
+    else x: x;
 
   traceWarning = msg:
     builtins.trace ("WARNING[haskell-flake] [${name}]: " + msg);

nix/modules/project/default.nix

@@ -40,20 +40,10 @@ in
         then builtins.baseNameOf config.projectRoot
         else cls;
     };
-    debug = mkOption {
-      type = types.bool;
-      default = false;
-      description = ''
-        Whether to enable verbose trace output from haskell-flake.
-
-        Useful for debugging.
-      '';
-    };
     log = mkOption {
       type = types.attrsOf (types.functionTo types.raw);
       default = import ../../logging.nix {
         name = config.projectFlakeName + "#haskellProjects." + name;
-        inherit (config) debug;
       };
       internal = true;
       readOnly = true;

test/simple/flake.nix

@@ -45,8 +45,6 @@
         haskellProjects.default = {
           # Multiple modules should be merged correctly.
           imports = [ self.haskellFlakeProjectModules.default ];
-          # Debug logging should work.
-          debug = true;
           packages = {
             # Because the module being imported above also defines a root for
             # the 'foo' package, we must override it here using `lib.mkForce`.