From 229ab7623e000f85f79e928dbdba5d57c587ffb2 Mon Sep 17 00:00:00 2001
From: Mathias Vorreiter Pedersen <mathiasvp@github.com>
Date: Tue, 5 Jan 2021 13:38:45 +0100
Subject: [PATCH] - Add pre-commit hook script to misc/scripts - Refer to it in
 CONTRIBUTING.md - Add setup note in docs folder

---
 CONTRIBUTING.md               |  2 ++
 docs/pre-commit-hook-setup.md | 13 +++++++++++++
 misc/scripts/pre-commit       | 18 ++++++++++++++++++
 3 files changed, 33 insertions(+)
 create mode 100644 docs/pre-commit-hook-setup.md
 create mode 100644 misc/scripts/pre-commit

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index fa88395e5d0..39552ad0bd9 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -38,6 +38,8 @@ If you have an idea for a query that you would like to share with other CodeQL u
 
     - The queries and libraries must be autoformatted, for example using the "Format Document" command in [CodeQL for Visual Studio Code](https://help.semmle.com/codeql/codeql-for-vscode/procedures/about-codeql-for-vscode.html).
 
+    If you prefer, you can use this [pre-commit hook](misc/scripts/pre-commit) that automatically checks whether your files are correctly formatted. See the [pre-commit hook installation guide](docs/install-pre-commit-hook.md) for instructions on how to install the hook.
+
 4. **Compilation**
 
     - Compilation of the query and any associated libraries and tests must be resilient to future development of the [supported](docs/supported-queries.md) libraries. This means that the functionality cannot use internal libraries, cannot depend on the output of `getAQlClass`, and cannot make use of regexp matching on `toString`.
diff --git a/docs/pre-commit-hook-setup.md b/docs/pre-commit-hook-setup.md
new file mode 100644
index 00000000000..d0c7fa5d1d3
--- /dev/null
+++ b/docs/pre-commit-hook-setup.md
@@ -0,0 +1,13 @@
+# CodeQL pre-commit-hook setup
+
+As stated in [CONTRIBUTING](../CONTRIBUTING.md) all CodeQL files must be formatted according to our [CodeQL style guide](ql-style-guide.md). You can use our pre-commit hook to avoid committing incorrectly formatted code. To use it, simply copy the [pre-commit](../misc/scripts/pre-commit) script to `.git/modules/ql/hooks/pre-commit` and make sure that it is executable.
+
+The script will abort a commit that contains incorrectly formatted code in .ql or .qll files and print an error message like:
+
+```
+> git commit -m "My commit."
+code/ql/cpp/ql/src/Options.qll would change by autoformatting.
+code/ql/cpp/ql/src/printAst.ql would change by autoformatting.
+```
+
+If you prefer to have the script automatically format the code (and not abort the commit), you can replace the line `codeql query format --check-only` with `codeql query format --in-place` (and `exit $exitVal` with `exit 0`).
diff --git a/misc/scripts/pre-commit b/misc/scripts/pre-commit
new file mode 100644
index 00000000000..e1492099519
--- /dev/null
+++ b/misc/scripts/pre-commit
@@ -0,0 +1,18 @@
+#!/bin/bash
+
+exec 1>&2
+exitVal=0
+while read -r f
+do
+  filename="${f##*/}"
+  extension="${filename##*.}"
+  p="$PWD/$f";
+  if [[ -f "$p" ]] && { [ "$extension" == "ql" ] || [ "$extension" == "qll" ]; }
+  then
+    if ! codeql query format --check-only "$p"
+    then
+      exitVal=1
+    fi
+  fi
+done <<<"$(git diff --cached --relative --name-only)"
+exit $exitVal