simplify.hs

-- tsDefaultCompiler :: [Identifier] -> Context String -> Item String -> Compiler (Item String)
-- tsDefaultCompiler 

siteIndexCompiler :: Context String -> Item String -> Compiler (Item String)
siteIndexCompiler ctx =
    loadAndApplyTemplate "templates/site-index.html" ctx
        >=> defaultCompiler ctx

sitePageCompiler :: Context String -> Item String -> Compiler (Item String)
sitePageCompiler ctx =
    loadAndApplyTemplate "templates/site-page.html" ctx
        >=> defaultCompiler ctx

defaultCompiler :: Context String -> Item String -> Compiler (Item String)
defaultCompiler ctx =
    loadAndApplyTemplate "templates/default.html" ctx
        >=> cleanAndRelUrls

tsDefaultCompiler ::
    [Identifier] ->
    Context String ->
    Item String ->
    Compiler (Item String)
tsDefaultCompiler ts ctx =
    foldM
        (\acc b -> acc >>= loadAndApplyTemplate b ctx)
        (empty :: Compiler (Item String))
        ts

siteIndexCompiler ::
    Context String ->
    Item String ->
    Compiler (Item String)
siteIndexCompiler ctx =
    tsDefaultCompiler ["templates/site-index.html", "templates/default.html"] ctx
        >=> cleanAndRelUrls

sitePageCompiler :: Context String -> Item String -> Compiler (Item String)
sitePageCompiler ctx =
    loadAndApplyTemplate "templates/site-page.html" ctx
        >=> defaultCompiler ctx

defaultCompiler :: Context String -> Item String -> Compiler (Item String)
defaultCompiler ctx =
    loadAndApplyTemplate "templates/default.html" ctx
        >=> cleanAndRelUrls

Here is error when I attempt to compile

6 of 7] Compiling Compilers        ( src/Compilers.hs, /Users/mmynsted/projects/bytesizedworkbench-hakyll/dist-newstyle/build/x86_64-osx/ghc-8.8.4/bytesizedworkbench-hakyll-0.1.0.0/x/site/build/site/site-tmp/Compilers.o )

src/Compilers.hs:22:5: error:
    • Couldn't match expected type ‘Item String
                                    -> Compiler (Item String)’
                  with actual type ‘Compiler (Compiler (Item String))’
    • Possible cause: ‘foldM’ is applied to too many arguments
      In the expression:
        foldM
          (\ acc b -> acc >>= loadAndApplyTemplate b ctx)
          (empty :: Compiler (Item String))
          ts
      In an equation for ‘tsDefaultCompiler’:
          tsDefaultCompiler ts ctx
            = foldM
                (\ acc b -> acc >>= loadAndApplyTemplate b ctx)
                (empty :: Compiler (Item String))
                ts
   |
22 |     foldM
   |     ^^^^^...

src/Compilers.hs:23:20: error:
    • Couldn't match type ‘Item’ with ‘Compiler’
      Expected type: Compiler (Compiler (Item String))
        Actual type: Compiler (Item String)
    • In the expression: acc >>= loadAndApplyTemplate b ctx
      In the first argument of ‘foldM’, namely
        ‘(\ acc b -> acc >>= loadAndApplyTemplate b ctx)’
      In the expression:
        foldM
          (\ acc b -> acc >>= loadAndApplyTemplate b ctx)
          (empty :: Compiler (Item String))
          ts
   |
23 |         (\acc b -> acc >>= loadAndApplyTemplate b ctx)

If I change the function like this

tsDefaultCompiler ::
    [Identifier] ->
    Context String ->
    Item String ->
    Compiler (Item String)
tsDefaultCompiler ts ctx =
    foldM
        (\acc b -> loadAndApplyTemplate b ctx)
        (empty :: Compiler (Item String))
        ts

Then it compiles but the result is always the empty.