Fix glob performance on large monorepos (purescript#1244)

The final patch goes back to the approach we had before purescript#1234, where we'd compose the glob-matching functions instead of keeping a list of ignores, and recompute the matchers when needed.

The patch in purescript#1234 was not optimised, as the matchers were being recreated for every file encountered, and optimising that in the first two commits of this PR got us down to 2x of the performance pre-1234.
That is unfortunately still not acceptable, so I reintroduced the function-composition approach, which is still prone to blowing the stack - the change here should reduce that risk, since instead of composing every line of gitignores as a separate matcher in the chain, we instead nest them in a single or block. That should dramatically reduce the size of the call chain.

Author: f-f

src/Spago/Command/Build.purs

@@ -153,8 +153,9 @@ run opts = do
     if Array.null pedanticPkgs || opts.depsOnly then
       pure true
     else do
-      logInfo $ "Looking for unused and undeclared transitive dependencies..."
+      logInfo "Looking for unused and undeclared transitive dependencies..."
       eitherGraph <- Graph.runGraph globs opts.pursArgs
+      logDebug "Decoded the output of `purs graph` successfully. Analyzing dependencies..."
       eitherGraph # either (prepareToDie >>> (_ $> false)) \graph -> do
         env <- ask
         checkResults <- map Array.fold $ for pedanticPkgs \(Tuple selected options) -> do

src/Spago/Glob.js

@@ -1,7 +1,7 @@
 import mm from 'micromatch';
 import * as fsWalk from '@nodelib/fs.walk';
 
-export const testGlob = glob => mm.matcher(glob.include, {ignore: glob.ignore});
+export const testGlob = glob => mm.matcher(glob.include, { ignore: glob.ignore });
 
 export const fsWalkImpl = Left => Right => respond => options => path => () => {
   const entryFilter = entry => options.entryFilter(entry)();
@@ -13,4 +13,3 @@ export const fsWalkImpl = Left => Right => respond => options => path => () => {
 };
 
 export const isFile = dirent => dirent.isFile();
-

src/Spago/Glob.purs

@@ -7,15 +7,13 @@ import Control.Monad.Maybe.Trans (runMaybeT)
 import Control.Monad.Trans.Class (lift)
 import Data.Array as Array
 import Data.Filterable (filter)
-import Data.Foldable (any, fold)
+import Data.Foldable (any, traverse_)
 import Data.String as String
-import Data.Traversable (traverse_)
+import Data.String as String.CodePoint
 import Effect.Aff as Aff
 import Effect.Ref as Ref
 import Node.FS.Sync as SyncFS
 import Node.Path as Path
-import Record as Record
-import Type.Proxy (Proxy(..))
 
 type Glob =
   { ignore :: Array String
@@ -30,8 +28,10 @@ splitGlob { ignore, include } = (\a -> { ignore, include: [ a ] }) <$> include
 type Entry = { name :: String, path :: String, dirent :: DirEnt }
 type FsWalkOptions = { entryFilter :: Entry -> Effect Boolean, deepFilter :: Entry -> Effect Boolean }
 
+-- https://nodejs.org/api/fs.html#class-fsdirent
 foreign import data DirEnt :: Type
 foreign import isFile :: DirEnt -> Boolean
+
 foreign import fsWalkImpl
   :: (forall a b. a -> Either a b)
   -> (forall a b. b -> Either a b)
@@ -40,32 +40,32 @@ foreign import fsWalkImpl
   -> String
   -> Effect Unit
 
-gitignoreGlob :: String -> String -> Glob
-gitignoreGlob base =
+gitignoreFileToGlob :: FilePath -> String -> Glob
+gitignoreFileToGlob base =
   String.split (String.Pattern "\n")
     >>> map String.trim
     >>> Array.filter (not <<< or [ String.null, isComment ])
     >>> partitionMap
       ( \line -> do
-          let
-            resolve a = Path.concat [ base, a ]
-            pat a = withForwardSlashes $ resolve $ unpackPattern a
+          let pattern lin = withForwardSlashes $ Path.concat [ base, gitignorePatternToGlobPattern lin ]
           case String.stripPrefix (String.Pattern "!") line of
-            Just negated -> Left $ pat negated
-            Nothing -> Right $ pat line
+            Just negated -> Left $ pattern negated
+            Nothing -> Right $ pattern line
       )
-    >>> Record.rename (Proxy @"left") (Proxy @"ignore")
-    >>> Record.rename (Proxy @"right") (Proxy @"include")
+    >>> (\{ left, right } -> { ignore: left, include: right })
 
   where
   isComment = isJust <<< String.stripPrefix (String.Pattern "#")
-  leadingSlash = String.stripPrefix (String.Pattern "/")
-  trailingSlash = String.stripSuffix (String.Pattern "/")
+  dropSuffixSlash str = fromMaybe str $ String.stripSuffix (String.Pattern "/") str
+  dropPrefixSlash str = fromMaybe str $ String.stripPrefix (String.Pattern "/") str
+
+  leadingSlash str = String.codePointAt 0 str == Just (String.CodePoint.codePointFromChar '/')
+  trailingSlash str = String.codePointAt (String.length str - 1) str == Just (String.CodePoint.codePointFromChar '/')
 
-  unpackPattern :: String -> String
-  unpackPattern pattern
-    | Just a <- trailingSlash pattern = unpackPattern a
-    | Just a <- leadingSlash pattern = a <> "/**"
+  gitignorePatternToGlobPattern :: String -> String
+  gitignorePatternToGlobPattern pattern
+    | trailingSlash pattern = gitignorePatternToGlobPattern $ dropSuffixSlash pattern
+    | leadingSlash pattern = dropPrefixSlash pattern <> "/**"
     | otherwise = "**/" <> pattern <> "/**"
 
 fsWalk :: String -> Array String -> Array String -> Aff (Array Entry)
@@ -74,41 +74,63 @@ fsWalk cwd ignorePatterns includePatterns = Aff.makeAff \cb -> do
 
   -- Pattern for directories which can be outright ignored.
   -- This will be updated whenver a .gitignore is found.
-  ignoreMatcherRef :: Ref Glob <- Ref.new { ignore: [], include: ignorePatterns }
+  ignoreMatcherRef :: Ref (String -> Boolean) <- Ref.new (testGlob { ignore: [], include: ignorePatterns })
 
   -- If this Ref contains `true` because this Aff has been canceled, then deepFilter will always return false.
   canceled <- Ref.new false
 
   let
-    entryGitignore :: Entry -> Effect Unit
-    entryGitignore entry =
-      try (SyncFS.readTextFile UTF8 entry.path)
-        >>= traverse_ \gitignore ->
-          let
-            base = Path.relative cwd $ Path.dirname entry.path
-            glob = gitignoreGlob base gitignore
-            pats = splitGlob glob
-            patOk g = not $ any (testGlob g) includePatterns
-            newPats = filter patOk pats
-          in
-            void $ Ref.modify (_ <> fold newPats) $ ignoreMatcherRef
+    -- Update the ignoreMatcherRef with the patterns from a .gitignore file
+    updateIgnoreMatcherWithGitignore :: Entry -> Effect Unit
+    updateIgnoreMatcherWithGitignore entry = do
+      let
+        gitignorePath = entry.path
+        -- directory of this .gitignore relative to the directory being globbed
+        base = Path.relative cwd (Path.dirname gitignorePath)
+
+      try (SyncFS.readTextFile UTF8 entry.path) >>= traverse_ \gitignore -> do
+        let
+          gitignored = testGlob <$> (splitGlob $ gitignoreFileToGlob base gitignore)
+
+          -- Do not add `.gitignore` patterns that explicitly ignore the files
+          -- we're searching for;
+          --
+          -- ex. if `includePatterns` is [".spago/p/aff-1.0.0/**/*.purs"],
+          -- and `gitignored` is ["node_modules", ".spago"],
+          -- then add "node_modules" to `ignoreMatcher` but not ".spago"
+          wouldConflictWithSearch matcher = any matcher includePatterns
+
+          newMatchers = or $ filter (not <<< wouldConflictWithSearch) gitignored
+
+          -- Another possible approach could be to keep a growing array of patterns and
+          -- regenerate the matcher on every gitignore. We have tried that (see #1234),
+          -- and turned out to be 2x slower. (see #1242, and #1244)
+          -- Composing functions is faster, but there's the risk of blowing the stack
+          -- (see #1231) - when this was introduced in #1210, every match from the
+          -- gitignore file would be `or`ed to the previous matcher, which would create
+          -- a very long (linear) call chain - in this latest iteration we are `or`ing the
+          -- new matchers together, then the whole thing with the previous matcher.
+          -- This is still prone to stack issues, but we now have a tree so it should
+          -- not be as dramatic.
+          addMatcher currentMatcher = or [ currentMatcher, newMatchers ]
+
+        Ref.modify_ addMatcher ignoreMatcherRef
 
     -- Should `fsWalk` recurse into this directory?
     deepFilter :: Entry -> Effect Boolean
     deepFilter entry = fromMaybe false <$> runMaybeT do
       isCanceled <- lift $ Ref.read canceled
       guard $ not isCanceled
-      shouldIgnore <- lift $ testGlob <$> Ref.read ignoreMatcherRef
+      shouldIgnore <- lift $ Ref.read ignoreMatcherRef
       pure $ not $ shouldIgnore $ Path.relative cwd entry.path
 
     -- Should `fsWalk` retain this entry for the result array?
     entryFilter :: Entry -> Effect Boolean
     entryFilter entry = do
-      when (isFile entry.dirent && entry.name == ".gitignore") (entryGitignore entry)
-      ignorePat <- Ref.read ignoreMatcherRef
-      let
-        ignoreMatcher = testGlob ignorePat
-        path = withForwardSlashes $ Path.relative cwd entry.path
+      when (isFile entry.dirent && entry.name == ".gitignore") do
+        updateIgnoreMatcherWithGitignore entry
+      ignoreMatcher <- Ref.read ignoreMatcherRef
+      let path = withForwardSlashes $ Path.relative cwd entry.path
       pure $ includeMatcher path && not (ignoreMatcher path)
 
     options = { entryFilter, deepFilter }

test/Spago/Glob.purs

@@ -92,10 +92,14 @@ spec = Spec.around globTmpDir do
 
       Spec.it "is stacksafe" \p -> do
         let
-          chars = [ "a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k" ]
-          -- 10,000-line gitignore
+          chars = [ "a", "b", "c", "d", "e", "f", "g", "h" ]
+          -- 4000-line gitignore
           words = [ \a b c d -> a <> b <> c <> d ] <*> chars <*> chars <*> chars <*> chars
           hugeGitignore = intercalate "\n" words
+        -- Write it in a few places
         FS.writeTextFile (Path.concat [ p, ".gitignore" ]) hugeGitignore
+        FS.writeTextFile (Path.concat [ p, "fruits", ".gitignore" ]) hugeGitignore
+        FS.writeTextFile (Path.concat [ p, "fruits", "left", ".gitignore" ]) hugeGitignore
+        FS.writeTextFile (Path.concat [ p, "fruits", "right", ".gitignore" ]) hugeGitignore
         a <- Glob.gitignoringGlob p [ "fruits/**/apple" ]
         Array.sort a `Assert.shouldEqual` [ "fruits/left/apple", "fruits/right/apple" ]