From e7c1e746187c2555a4fde6db0810b6441a804f87 Mon Sep 17 00:00:00 2001
From: Folkert <folkert@folkertdev.nl>
Date: Fri, 8 Nov 2019 19:57:18 +0100
Subject: [PATCH 1/3] Fix #642 Bad performance/memory leak for long list
 literals

A one-character fix that speeds up the formatting of long literals
and drastically reduces memory usage.

A very simple example is

```elm
module Small exposing (x)

x =
    [ 1, 2, 3
     , 4]
```

But with a list literal of many thousands of elements. The newline
forces all elements to get their own line. This is implemented as a
fold, but in practice this would often perform

```
longList ++ shortList
```

By reversing the fold (from `foldl` to `foldr`) that turns into

```
shortList ++ longList
```

Which requires less traversals and memory.
---
 src/Box.hs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Box.hs b/src/Box.hs
index 74bd45fd0..3f0645f66 100644
--- a/src/Box.hs
+++ b/src/Box.hs
@@ -119,7 +119,7 @@ stack1 children =
         [first] ->
             first
         boxes ->
-            foldl1 stack' boxes
+            foldr1 stack' boxes
 
 
 mapLines :: (Line -> Line) -> Box -> Box

From fdc913c4fe3f55aacb6f9ad6ca0be33441e7cdb1 Mon Sep 17 00:00:00 2001
From: Aaron VonderHaar <gruen0aermel@gmail.com>
Date: Thu, 14 Nov 2019 20:59:38 -0800
Subject: [PATCH 2/3] Add scripts for profiling test files

---
 .gitignore   |  1 +
 Shakefile.hs | 36 +++++++++++++++++++++++++++++++++++-
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/.gitignore b/.gitignore
index 72332601c..382837014 100644
--- a/.gitignore
+++ b/.gitignore
@@ -8,3 +8,4 @@
 /.shake/
 /_build/
 /generated/
+/_profile/
diff --git a/Shakefile.hs b/Shakefile.hs
index 55a5c000e..cbc75bbe3 100644
--- a/Shakefile.hs
+++ b/Shakefile.hs
@@ -14,6 +14,8 @@ main = do
     } $ do
     StdoutTrim stackLocalInstallRoot <- liftIO $ cmd "stack path --local-install-root"
     StdoutTrim stackLocalBin <- liftIO $ cmd "stack path --local-bin"
+    StdoutTrim gitDescribe <- liftIO $ cmd "git" [ "describe", "--abbrev=8", "--always" ]
+    StdoutTrim gitSha <- liftIO $ cmd "git" [ "describe", "--always", "--match", "NOT A TAG", "--dirty" ]
 
     let elmFormat = stackLocalInstallRoot </> "bin/elm-format" <.> exe
     let shellcheck = stackLocalBin </> "shellcheck" <.> exe
@@ -29,6 +31,7 @@ main = do
 
     phony "build" $ need [ elmFormat ]
     phony "stack-test" $ need [ "_build/stack-test.ok" ]
+    phony "profile" $ need [ "_build/tests/test-files/prof.ok" ]
 
     phony "clean" $ do
         cmd_ "stack clean"
@@ -56,7 +59,6 @@ main = do
 
     "generated/Build_elm_format.hs" %> \out -> do
         alwaysRerun
-        (StdoutTrim gitDescribe) <- cmd "git" [ "describe", "--abbrev=8", "--always" ]
         writeFileChanged out $ unlines
             [ "module Build_elm_format where"
             , ""
@@ -70,6 +72,15 @@ main = do
         need generatedSourceFiles
         cmd_ "stack build --test --no-run-tests"
 
+    "_build/bin/elm-format-prof" %> \out -> do
+        StdoutTrim profileInstallRoot <- liftIO $ cmd "stack path --profile --local-install-root"
+        sourceFiles <- getDirectoryFiles "" sourceFilesPattern
+        need sourceFiles
+        need generatedSourceFiles
+        cmd_ "stack build --profile --executable-profiling --library-profiling"
+        copyFileChanged (profileInstallRoot </> "bin/elm-format" <.> exe) out
+
+
     --
     -- Haskell tests
     --
@@ -124,6 +135,15 @@ main = do
         cmd_ ("bash" <.> exe) script elmFormat
         writeFile' out ""
 
+    "_build/tests/test-files/prof.ok" %> \out -> do
+        let oks =
+              [ "_build/tests/test-files/good/Elm-0.17/prof.ok"
+              , "_build/tests/test-files/good/Elm-0.18/prof.ok"
+              , "_build/tests/test-files/good/Elm-0.19/prof.ok"
+              ]
+        need oks
+        writeFile' out (unlines oks)
+
 
     -- Elm files
 
@@ -138,6 +158,20 @@ main = do
             need oks
             writeFile' out (unlines elmFiles)
 
+        ("_build/tests/test-files/good/Elm-" ++ elmVersion ++ "/prof.ok") %> \out -> do
+            alwaysRerun
+            elmFiles <- getDirectoryFiles ""
+                [ "tests/test-files/good/Elm-" ++ elmVersion ++ "//*.elm"
+                ]
+            let oks = ["_profile" </> f -<.> (gitSha ++ ".prof") | f <- elmFiles]
+            need oks
+            writeFile' out (unlines oks)
+
+        ("_profile/tests/test-files/good/Elm-" ++ elmVersion ++ "//*." ++ gitSha ++ ".prof") %> \out -> do
+            let source = dropDirectory1 $ dropExtensions out <.> "elm"
+            need [ "_build/bin/elm-format-prof", source ]
+            cmd_ "_build/bin/elm-format-prof" source "--output" "/dev/null" ("--elm-version=" ++ elmVersion) "+RTS" "-p" ("-po" ++ (out -<.> ""))
+
         ("_build/tests/test-files/*/Elm-" ++ elmVersion ++ "//*.elm_formatted") %> \out -> do
             let source = dropDirectory1 $ out -<.> "elm"
             need [ elmFormat, source ]

From f79639262ed4e09e55a23a4a05daf2a7a0b02248 Mon Sep 17 00:00:00 2001
From: Aaron VonderHaar <gruen0aermel@gmail.com>
Date: Thu, 14 Nov 2019 21:30:53 -0800
Subject: [PATCH 3/3] Update CHANGELOG

---
 CHANGELOG.md | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index c8afec05b..773c37569 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,9 @@
+## master
+
+Bug fixes:
+  - performance is improved, allowing excessively long lists to be formatted without crashing
+
+
 ## 0.8.2
 
 New features: