From 0dbeaaf18708a882a2e7e513e57a910b4855cc75 Mon Sep 17 00:00:00 2001
From: Valentin Maerten <maerten.valentin@gmail.com>
Date: Fri, 26 Dec 2025 21:02:33 +0100
Subject: [PATCH] feat(taskfile): skip var merge when SCOPED_INCLUDES enabled

When the SCOPED_INCLUDES experiment is enabled, variables from included
Taskfiles are no longer merged globally. They remain in their original
Taskfile within the DAG.

Exception: flatten includes still merge variables globally to allow
sharing common variables across multiple Taskfiles.
---
 setup.go                 |  3 ++-
 taskfile/ast/graph.go    |  5 ++++-
 taskfile/ast/taskfile.go | 12 ++++++++----
 3 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/setup.go b/setup.go
index 8b3eca10..b1940886 100644
--- a/setup.go
+++ b/setup.go
@@ -20,6 +20,7 @@ import (
 	"github.com/go-task/task/v3/internal/logger"
 	"github.com/go-task/task/v3/internal/output"
 	"github.com/go-task/task/v3/internal/version"
+	"github.com/go-task/task/v3/experiments"
 	"github.com/go-task/task/v3/taskfile"
 	"github.com/go-task/task/v3/taskfile/ast"
 )
@@ -105,7 +106,7 @@ func (e *Executor) readTaskfile(node taskfile.Node) error {
 		return err
 	}
 	e.Graph = graph
-	if e.Taskfile, err = graph.Merge(); err != nil {
+	if e.Taskfile, err = graph.Merge(experiments.ScopedIncludes.Enabled()); err != nil {
 		return err
 	}
 	return nil
diff --git a/taskfile/ast/graph.go b/taskfile/ast/graph.go
index b6c27438..ab961b7d 100644
--- a/taskfile/ast/graph.go
+++ b/taskfile/ast/graph.go
@@ -57,7 +57,9 @@ func (tfg *TaskfileGraph) Root() (*TaskfileVertex, error) {
 	return tfg.Vertex(hashes[0])
 }
 
-func (tfg *TaskfileGraph) Merge() (*Taskfile, error) {
+// Merge merges all included Taskfiles into the root Taskfile.
+// If skipVarsMerge is true, variables are not merged (used for scoped includes).
+func (tfg *TaskfileGraph) Merge(skipVarsMerge bool) (*Taskfile, error) {
 	hashes, err := graph.TopologicalSort(tfg.Graph)
 	if err != nil {
 		return nil, err
@@ -104,6 +106,7 @@ func (tfg *TaskfileGraph) Merge() (*Taskfile, error) {
 					if err := vertex.Taskfile.Merge(
 						includedVertex.Taskfile,
 						include,
+						skipVarsMerge,
 					); err != nil {
 						return err
 					}
diff --git a/taskfile/ast/taskfile.go b/taskfile/ast/taskfile.go
index 4ae1dbac..a56d2262 100644
--- a/taskfile/ast/taskfile.go
+++ b/taskfile/ast/taskfile.go
@@ -36,8 +36,9 @@ type Taskfile struct {
 	Interval time.Duration
 }
 
-// Merge merges the second Taskfile into the first
-func (t1 *Taskfile) Merge(t2 *Taskfile, include *Include) error {
+// Merge merges the second Taskfile into the first.
+// If skipVarsMerge is true, variables are not merged (used for scoped includes).
+func (t1 *Taskfile) Merge(t2 *Taskfile, include *Include, skipVarsMerge bool) error {
 	if !t1.Version.Equal(t2.Version) {
 		return fmt.Errorf(`task: Taskfiles versions should match. First is "%s" but second is "%s"`, t1.Version, t2.Version)
 	}
@@ -67,8 +68,11 @@ func (t1 *Taskfile) Merge(t2 *Taskfile, include *Include) error {
 			}
 		}
 	}
-	t1.Vars.Merge(t2.Vars, include)
-	t1.Env.Merge(t2.Env, include)
+	// Only merge vars if not using scoped includes, or if flattening
+	if !skipVarsMerge || include.Flatten {
+		t1.Vars.Merge(t2.Vars, include)
+		t1.Env.Merge(t2.Env, include)
+	}
 	return t1.Tasks.Merge(t2.Tasks, include, t1.Vars)
 }