Add programmatic model builder API

builder_test.go

@@ -0,0 +1,74 @@
+// Copyright 2026 The casbin Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package casbin
+
+import (
+	"testing"
+
+	"github.com/casbin/casbin/v3/model"
+	fileadapter "github.com/casbin/casbin/v3/persist/file-adapter"
+)
+
+// TestBuilderRBAC tests the builder version of the RBAC model.
+func TestBuilderRBAC(t *testing.T) {
+	// Build the RBAC model programmatically
+	m, _ := model.New().
+		Request("sub", "obj", "act").
+		Policy("sub", "obj", "act").
+		Role("_", "_").
+		Effect("some(where (p.eft == allow))").
+		Matcher("g(r.sub, p.sub) && r.obj == p.obj && r.act == p.act").
+		Build()
+
+	// Use the same policy file as the original test
+	a := fileadapter.NewAdapter("examples/rbac_policy.csv")
+	e, _ := NewEnforcer(m, a)
+
+	// Same test cases as TestRBACModel
+	testEnforce(t, e, "alice", "data1", "read", true)
+	testEnforce(t, e, "alice", "data1", "write", false)
+	testEnforce(t, e, "alice", "data2", "read", true)
+	testEnforce(t, e, "alice", "data2", "write", true)
+	testEnforce(t, e, "bob", "data1", "read", false)
+	testEnforce(t, e, "bob", "data1", "write", false)
+	testEnforce(t, e, "bob", "data2", "read", false)
+	testEnforce(t, e, "bob", "data2", "write", true)
+}
+
+// TestBuilderABAC tests the builder version of the ABAC model.
+func TestBuilderABAC(t *testing.T) {
+	// Build the ABAC model programmatically
+	m, _ := model.New().
+		Request("sub", "obj", "act").
+		Policy("sub", "obj", "act").
+		Effect("some(where (p.eft == allow))").
+		Matcher("r.sub == r.obj.Owner").
+		Build()
+
+	e, _ := NewEnforcer(m)
+
+	data1 := newTestResource("data1", "alice")
+	data2 := newTestResource("data2", "bob")
+
+	// Same test cases as TestABACModel
+	testEnforce(t, e, "alice", data1, "read", true)
+	testEnforce(t, e, "alice", data1, "write", true)
+	testEnforce(t, e, "alice", data2, "read", false)
+	testEnforce(t, e, "alice", data2, "write", false)
+	testEnforce(t, e, "bob", data1, "read", false)
+	testEnforce(t, e, "bob", data1, "write", false)
+	testEnforce(t, e, "bob", data2, "read", true)
+	testEnforce(t, e, "bob", data2, "write", true)
+}

model/builder.go

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+// Copyright 2026 The casbin Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package model
+
+import (
+	"strings"
+)
+
+// Builder provides a programmatic way to construct Casbin models.
+// It allows creating models without needing a model.conf file.
+//
+// Example usage:
+//
+//	m, _ := model.New().
+//	    Request("sub", "obj", "act").
+//	    Policy("sub", "obj", "act").
+//	    Role("_", "_").
+//	    Effect("some(where (p.eft == allow))").
+//	    Matcher("g(r.sub, p.sub) && r.obj == p.obj && r.act == p.act").
+//	    Build()
+//
+// The resulting model is equivalent to one loaded from a model.conf file.
+type Builder struct {
+	requestDef string
+	policyDef  string
+	roleDef    string
+	effectDef  string
+	matcherDef string
+}
+
+// New creates a new model builder.
+func New() *Builder {
+	return &Builder{}
+}
+
+// Request sets the request definition with the provided fields.
+// Example: Request("sub", "obj", "act")
+func (b *Builder) Request(fields ...string) *Builder {
+	b.requestDef = strings.Join(fields, ", ")
+	return b
+}
+
+// Policy sets the policy definition with the provided fields.
+// Example: Policy("sub", "obj", "act")
+func (b *Builder) Policy(fields ...string) *Builder {
+	b.policyDef = strings.Join(fields, ", ")
+	return b
+}
+
+// Role sets the role definition.
+// Example: Role("_", "_") for basic RBAC
+func (b *Builder) Role(fields ...string) *Builder {
+	b.roleDef = strings.Join(fields, ", ")
+	return b
+}
+
+// Effect sets the policy effect.
+// Example: Effect("some(where (p.eft == allow))")
+func (b *Builder) Effect(effect string) *Builder {
+	b.effectDef = effect
+	return b
+}
+
+// Matcher sets the matcher expression.
+// Example: Matcher("r.sub == p.sub && r.obj == p.obj && r.act == p.act")
+func (b *Builder) Matcher(matcher string) *Builder {
+	b.matcherDef = matcher
+	return b
+}
+
+// Build creates a Model from the builder configuration.
+func (b *Builder) Build() (Model, error) {
+	m := NewModel()
+
+	if b.requestDef != "" {
+		m.AddDef("r", "r", b.requestDef)
+	}
+
+	if b.policyDef != "" {
+		m.AddDef("p", "p", b.policyDef)
+	}
+
+	if b.roleDef != "" {
+		m.AddDef("g", "g", b.roleDef)
+	}
+
+	if b.effectDef != "" {
+		m.AddDef("e", "e", b.effectDef)
+	}
+
+	if b.matcherDef != "" {
+		m.AddDef("m", "m", b.matcherDef)
+	}
+
+	return m, nil
+}
+
+// ToString returns the model as a string in CONF format.
+func (b *Builder) ToString() string {
+	var sb strings.Builder
+
+	sb.WriteString("[request_definition]\n")
+	if b.requestDef != "" {
+		sb.WriteString("r = ")
+		sb.WriteString(b.requestDef)
+		sb.WriteString("\n")
+	}
+	sb.WriteString("\n")
+
+	sb.WriteString("[policy_definition]\n")
+	if b.policyDef != "" {
+		sb.WriteString("p = ")
+		sb.WriteString(b.policyDef)
+		sb.WriteString("\n")
+	}
+	sb.WriteString("\n")
+
+	if b.roleDef != "" {
+		sb.WriteString("[role_definition]\n")
+		sb.WriteString("g = ")
+		sb.WriteString(b.roleDef)
+		sb.WriteString("\n\n")
+	}
+
+	sb.WriteString("[policy_effect]\n")
+	if b.effectDef != "" {
+		sb.WriteString("e = ")
+		sb.WriteString(b.effectDef)
+		sb.WriteString("\n")
+	}
+	sb.WriteString("\n")
+
+	sb.WriteString("[matchers]\n")
+	if b.matcherDef != "" {
+		sb.WriteString("m = ")
+		sb.WriteString(b.matcherDef)
+		sb.WriteString("\n")
+	}
+
+	return sb.String()
+}