fix(terraform_validate): Add better workaround for deal with parallelism race conditions in Terraform setups during t init: allow use of tofu binary just for t init, as OpenTofu 1.10+ have native lock mechanism

Author: MaxymVlasov

README.md

@@ -970,7 +970,15 @@ To replicate functionality in `terraform_docs` hook:
 ### terraform_validate
 
 > [!IMPORTANT]
-> If you use [`TF_PLUGIN_CACHE_DIR`](https://developer.hashicorp.com/terraform/cli/config/config-file#provider-plugin-cache), we recommend enabling `--hook-config=--retry-once-with-cleanup=true` or disabling parallelism (`--hook-config=--parallelism-limit=1`) to avoid [race conditions when `terraform init` writes to it](https://github.com/hashicorp/terraform/issues/31964).
+> If you use both:
+>
+> 1. Global Provider Cache. [Terraform docs](https://developer.hashicorp.com/terraform/cli/config/config-file#provider-plugin-cache), [OpenTofu docs](https://opentofu.org/docs/cli/config/config-file/#provider-plugin-cache)
+> 2.`tofu` < v1.10 or any `terraform` version
+>
+> We recommend to do one of:
+>
+> * Disable parallelism (`--hook-config=--parallelism-limit=1`) as it can cause [race conditions when `terraform init` writes to it](https://github.com/hashicorp/terraform/issues/31964).
+> * Install [OpenTofu v1.10+](https://opentofu.org/blog/help-us-test-opentofu-1-10-0-alpha2/#global-provider-cache-locking) even if you use Terraform - it will be used just for `t init` operations.
 
 1. `terraform_validate` supports custom arguments so you can pass supported `-no-color` or `-json` flags:
 

hooks/_common.sh

@@ -555,6 +555,15 @@ function common::terraform_init {
       init_output=$("$tf_path" init -backend=false "${TF_INIT_ARGS[@]}" 2>&1)
       exit_code=$?
     else
+      # The global provider cache is safe for concurrent use by multiple processes for OpenTofu v1.10+
+      # More details - https://github.com/opentofu/opentofu/pull/1878
+      # For that reason, we switch to `tofu init` when possible
+      if [[ "$($tf_path -version | head -1 | grep '^Terraform')" == "Terraform" ]] &&
+        common::tofu_version_ge_1.10; then
+        tf_path=$(command -v tofu)
+        common::colorify "green" "Using OpenTofu binary ($tf_path) for Terraform init operations, as it supports concurrent provider initialization."
+      fi
+
       # Locking just doesn't work, and the below works quicker instead. Details:
       # https://github.com/hashicorp/terraform/issues/31964#issuecomment-1939869453
       for i in {1..10}; do
@@ -609,6 +618,37 @@ function common::export_provided_env_vars {
   done
 }
 
+#######################################################################
+# Check if the installed Tofu version is >=1.10.0 or not
+#
+# This function helps to determine if tofu version allow to use
+# parallelism based on Tofu version
+#
+# Returns:
+#   - 0 if version >= 1.10.0
+#   - 1 if version < 1.10.0
+#    Defaults to 1 if version cannot be determined
+#######################################################################
+# TODO: Drop after Jun 2027. Two years to upgrade is more than enough.
+function common::tofu_version_ge_1.10 {
+  local tofu_version
+
+  # Extract version number (e.g., "tofu version v1.10.4" -> "1.10")
+  tofu_version=$(tofu --version 2> /dev/null | grep -oE '[0-9]+\.[0-9]+')
+  # If we can't parse version, default to older command
+  [[ ! $tofu_version ]] && return 1
+
+  local major minor
+  IFS='.' read -r major minor <<< "$tofu_version"
+
+  # New functional added in v1.10.0 (June 2025)
+  if [[ $major -gt 1 || ($major -eq 1 && $minor -ge 10) ]]; then
+    return 0
+  else
+    return 1
+  fi
+}
+
 #######################################################################
 # Check if the installed Terragrunt version is >=0.78.0 or not
 #