Make it compile with MicroHs.

.github/workflows/mhs-ci.yml

@@ -0,0 +1,59 @@
+name: mhs-ci
+
+on:
+  push:
+    branches: [ "master" ]
+  pull_request:
+    branches: [ "master" ]
+
+jobs:
+  build-mhs-prettyprinter:
+    runs-on: ubuntu-latest
+    steps:
+
+    - name: checkout mhs repo
+      uses: actions/checkout@v4
+      with:
+        repository: augustss/MicroHs
+        ref: v0.15.4.0
+        path: mhs
+    - name: make and install mhs
+      run: |
+        cd mhs
+        make minstall
+        echo "$HOME/.mcabal/bin" >> "$GITHUB_PATH"
+
+    # prettyprinter
+    - name: checkout prettyprinter repo
+      uses: actions/checkout@v4
+      with:
+        path: prettyprinter
+
+    - name: compile and install prettyprinter package
+      run: |
+        cd prettyprinter/prettyprinter
+        mcabal -r install
+
+    - name: compile and install prettyprinter-ansi-terminal package
+      run: |
+        cd prettyprinter/prettyprinter-ansi-terminal
+        mcabal -r install
+
+    - name: compile and install prettyprinter-compat-annotated-wl-pprint package
+      run: |
+        cd prettyprinter/prettyprinter-compat-annotated-wl-pprint
+        mcabal -r install
+
+    - name: compile and install prettyprinter-compat-ansi-wl-pprint package
+      run: |
+        cd prettyprinter/prettyprinter-compat-ansi-wl-pprint
+        mcabal -r install
+
+    - name: compile and install prettyprinter-compat-wl-pprint package
+      run: |
+        cd prettyprinter/prettyprinter-compat-wl-pprint
+        mcabal -r install
+
+    - name: cleanup
+      run: |
+        rm -rf $HOME/.mcabal

misc/version-compatibility-macros.h

@@ -9,7 +9,7 @@
 -- purpose much clearer than just demanding a specific version of a library.
 
 #define APPLICATIVE_MONAD               MIN_VERSION_base(4,8,0)
-#define FOLDABLE_TRAVERSABLE_IN_PRELUDE MIN_VERSION_base(4,8,0)
+#define FOLDABLE_TRAVERSABLE_IN_PRELUDE (MIN_VERSION_base(4,8,0) && !defined(__MHS__))
 #define FUNCTOR_IDENTITY_IN_BASE        MIN_VERSION_base(4,8,0)
 #define MONOID_IN_PRELUDE               MIN_VERSION_base(4,8,0)
 #define NATURAL_IN_BASE                 MIN_VERSION_base(4,8,0)

prettyprinter-ansi-terminal/prettyprinter-ansi-terminal.cabal

@@ -60,7 +60,7 @@ library
 
     if impl(ghc >= 8.0)
         ghc-options: -Wcompat
-    if !impl(ghc >= 8.0)
+    if !impl(ghc >= 8.0) && !impl(mhs)
         build-depends: semigroups >= 0.1
 
 test-suite doctest

prettyprinter-compat-ansi-wl-pprint/prettyprinter-compat-ansi-wl-pprint.cabal

@@ -34,5 +34,5 @@ library
         , prettyprinter               >= 1.7.0
         , prettyprinter-ansi-terminal >= 1.1
 
-    if !impl(ghc >= 8.0)
+    if !impl(ghc >= 8.0) && !impl(mhs)
         build-depends: semigroups >= 0.1

prettyprinter-compat-wl-pprint/prettyprinter-compat-wl-pprint.cabal

@@ -32,5 +32,5 @@ library
         , text          >= 1.2
         , prettyprinter >= 1.7.0
 
-    if !impl(ghc >= 8.0)
+    if !impl(ghc >= 8.0) && !impl(mhs)
         build-depends: semigroups >= 0.1

prettyprinter/prettyprinter.cabal

@@ -80,19 +80,18 @@ library
             , Data.Text.Lazy
             , Data.Text.Lazy.Builder
 
-    if !impl(ghc >= 7.6)
+    if !impl(ghc >= 7.6) && !impl(mhs)
         build-depends: ghc-prim
 
     if impl(ghc >= 8.0)
         ghc-options: -Wcompat
-    if !impl(ghc >= 8.0)
+    if !impl(ghc >= 8.0) && !impl(mhs)
         build-depends: semigroups >= 0.17
         build-depends: fail >= 4.9.0.0 && <4.10
-    if !impl(ghc >= 7.10)
+    if !impl(ghc >= 7.10) && !impl(mhs)
         build-depends: void >=0.4 && <0.8
 
 
-
 Flag buildReadme
   Description: Build the readme generator
   Default:     False

prettyprinter/src/Prettyprinter/Internal.hs

@@ -108,7 +108,7 @@ import Numeric.Natural
 #if !(FOLDABLE_TRAVERSABLE_IN_PRELUDE)
 import Data.Foldable    (Foldable (..))
 import Data.Traversable (Traversable (..))
-import Prelude          hiding (foldr, foldr1)
+import Prelude          hiding (null, foldr, foldr1)
 #endif
 
 #if FUNCTOR_IDENTITY_IN_BASE