Add scripts and instructions for switching between tree-sitter versions

.gitignore

@@ -21,5 +21,9 @@ _build
 /tree-sitter-config.mk
 /tree-sitter-config.sh
 
-# The installation root of tree-sitter
+# The default installation root of tree-sitter
 /tree-sitter
+/tree-sitter-*.*.*
+
+# The file containing the tree-sitter version being used
+/tree-sitter-version

Makefile

@@ -18,6 +18,8 @@ build:
 #
 .PHONY: setup
 setup:
+	test -f tree-sitter-version \
+	|| cp tree-sitter-version.default tree-sitter-version
 	./scripts/check-prerequisites
 	./scripts/install-tree-sitter-cli
 	./scripts/install-tree-sitter-lib

README.md

@@ -61,6 +61,20 @@ $ make setup
 $ ./scripts/rebuild-everything  # needs root access to install libtree-sitter
 ```
 
+### tree-sitter version
+
+The default tree-sitter version to use is in the
+`tree-sitter-version.default` file.
+
+Under the default configuration used for local development purposes,
+the version being actually used is stored in the file
+`tree-sitter-version`. This can be changed by invoking
+`./scripts/switch-tree-sitter-version` before `make setup`.
+We made this available to facilitate the transition from tree-sitter 0.20.6 to
+0.22.6 in ocaml-tree-sitter-semgrep where the integration of some
+grammars needs to be updated. The latest version of these grammars are
+compatible with 0.22.6 but their OCaml integration in Semgrep needs work.
+
 Documentation
 --
 

scripts/download-tree-sitter

@@ -6,11 +6,6 @@ set -eu -o pipefail
 
 prog_name=$(basename "$0")
 
-# The official version of tree-sitter we use for the code generator and
-# for the runtime library. Please try to keep this as the single source
-# of truth.
-default_version="0.22.6"
-
 error() {
   echo "Current directory: $(pwd)" >&2
   echo "Error: $@" >&2
@@ -27,16 +22,10 @@ Options:
       exists locally for the specified version.
   --help
       Show this message and exit.
-  --version VERSION
-      Install this specific version of tree-sitter. VERSION must be a git tag
-      or a branch name in the original tree-sitter repository.
-      See valid tags at https://github.com/tree-sitter/tree-sitter/tags
-      Current default: $default_version
 EOF
 }
 
 lazy=false
-version="$default_version"
 while [[ $# -gt 0 ]]; do
   case "$1" in
     --lazy)
@@ -46,16 +35,14 @@ while [[ $# -gt 0 ]]; do
       usage
       exit 0
       ;;
-    --version)
-      version="$2"
-      shift
-      ;;
     *)
       error "Invalid argument passed to '${prog_name}': '$1'"
   esac
   shift
 done
 
+version=$(cat tree-sitter-version)
+
 mkdir -p downloads
 (
   cd downloads
@@ -67,14 +54,6 @@ mkdir -p downloads
     rm -rf "$src_dir"
   fi
 
-  unversioned_src_dir=tree-sitter
-  cat <<EOF
-Creating version-independent symlink for homebrew packager:
-  $(pwd)/$unversioned_src_dir
-EOF
-  rm -f "$unversioned_src_dir"
-  ln -s "$src_dir" "$unversioned_src_dir"
-
   if [[ -d "$src_dir" ]]; then
     cat <<EOF
 Re-using tree-sitter sources found locally:

scripts/install-tree-sitter-cli

@@ -49,6 +49,7 @@ done
 bindir="$prefix"/bin
 
 dir_name=$(dirname "$BASH_SOURCE")
+"$dir_name"/update-version-symlinks
 "$dir_name"/download-tree-sitter --lazy
 
 (

scripts/install-tree-sitter-lib

@@ -49,6 +49,7 @@ done
 libdir="$prefix"/lib
 
 dir_name=$(dirname "$BASH_SOURCE")
+"$dir_name"/update-version-symlinks
 "$dir_name"/download-tree-sitter --lazy
 
 (

scripts/switch-tree-sitter-version

@@ -0,0 +1,35 @@
+#! /usr/bin/env bash
+#
+# Change the tree-sitter version used for local development and rebuild
+# what's necessary.
+#
+set -eu
+
+error() {
+  (
+    echo "[$0] Error: $*"
+    echo "Supported versions: 0.20.6 0.22.6"
+  )
+  exit 1
+}
+
+if [[ $# -ne 1 ]]; then
+  error "Exactly one argument is expected, the tree-sitter version ID"
+fi
+
+version=''
+case "$1" in
+  0.20.6)
+    version=0.20.6
+    ;;
+  0.22.6)
+    version=0.22.6
+    ;;
+  *)
+    error "Unsupported version '$1'"
+esac
+
+echo "$version" > tree-sitter-version
+./scripts/update-version-symlinks
+
+echo "You can now run 'make setup' to download and build tree-sitter $version."

scripts/update-version-symlinks

@@ -0,0 +1,41 @@
+#! /usr/bin/env bash
+#
+# Run this script to update local symlinks after changing the tree-sitter
+# version in the file 'tree-sitter-version'.
+#
+# This facilitates development that requires switching between different
+# tree-sitter versions. The compiled tree-sitter libraries and binaries
+# go into a versioned folder e.g. tree-sitter-0.22.6 and are therefore
+# preserved when switching back and forth between versions. 
+#
+# If the user wishes to install the tree-sitter CLI or runtime library
+# elsewhere than the default 'tree-sitter/', they can do so by passing the
+# '--prefix' option. In this case, the symlinks we create here become
+# irrelevant.
+#
+set -eu
+
+version=$(cat tree-sitter-version)
+
+echo "Updating symlinks 'downloads/tree-sitter' and 'tree-sitter'"
+
+(
+  cd downloads
+  rm -f tree-sitter
+  ln -s tree-sitter-"$version" tree-sitter
+)
+
+if [[ -d tree-sitter ]] && [[ ! -L tree-sitter ]]; then
+  # The issue is that we want to be able to use two different versions of
+  # the tree-sitter CLI. To make this convenient, the 'tree-sitter' folder
+  # is now a symlink to the versioned folder name.
+  echo "*** Your tree-sitter installation is old. Removing it."
+  rm -rf tree-sitter
+fi
+
+# Remove the symlink and set it to the new install folder.
+# It allows us to use this script to switch tree-sitter versions without
+# rebuilding everything.
+rm -f tree-sitter
+ln -s tree-sitter-"$version" tree-sitter
+mkdir -p tree-sitter-"$version"

tree-sitter-version.default

@@ -0,0 +1 @@
+0.22.6