Add support to create schema for variables (#49)

Given a map of module variables, create the corresponding body
schema with the corresponding variables as attribute schemas.

Related to hashicorp/terraform-ls#50.

schema/variable_schema.go

@@ -0,0 +1,25 @@
+package schema
+
+import (
+	"github.com/hashicorp/hcl-lang/lang"
+	"github.com/hashicorp/hcl-lang/schema"
+	"github.com/hashicorp/terraform-schema/module"
+)
+
+func SchemaForVariables(vars map[string]module.Variable) (*schema.BodySchema, error) {
+	varSchemas := make(map[string]*schema.AttributeSchema)
+
+	for name, v := range vars {
+		varSchemas[name] = &schema.AttributeSchema{
+			Description: lang.MarkupContent{
+				Value: v.Description,
+				Kind:  lang.PlainTextKind,
+			},
+			Expr: schema.ExprConstraints{schema.LiteralTypeExpr{Type: v.Type}},
+		}
+	}
+
+	return &schema.BodySchema{
+		Attributes: varSchemas,
+	}, nil
+}

schema/variable_schema_test.go

@@ -0,0 +1,89 @@
+package schema
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+	"github.com/hashicorp/hcl-lang/lang"
+	"github.com/hashicorp/hcl-lang/schema"
+	"github.com/hashicorp/terraform-schema/module"
+	"github.com/zclconf/go-cty-debug/ctydebug"
+	"github.com/zclconf/go-cty/cty"
+)
+
+func TestSchemaForVariables(t *testing.T) {
+	testCases := []struct {
+		name           string
+		variables      map[string]module.Variable
+		expectedSchema *schema.BodySchema
+	}{
+		{
+			"empty schema",
+			make(map[string]module.Variable),
+			&schema.BodySchema{Attributes: make(map[string]*schema.AttributeSchema)},
+		},
+		{
+			"one attribute schema",
+			map[string]module.Variable{
+				"name": module.Variable{
+					Description: "name of the module",
+					Type:        cty.String,
+				},
+			},
+			&schema.BodySchema{Attributes: map[string]*schema.AttributeSchema{
+				"name": &schema.AttributeSchema{
+					Description: lang.MarkupContent{
+						Value: "name of the module",
+						Kind:  lang.PlainTextKind,
+					},
+					Expr: schema.ExprConstraints{schema.LiteralTypeExpr{cty.String}},
+				},
+			}},
+		},
+		{
+			"two attribute schema",
+			map[string]module.Variable{
+				"name": module.Variable{
+					Description: "name of the module",
+					Type:        cty.String,
+				},
+				"id": module.Variable{
+					Description: "id of the module",
+					Type:        cty.Number,
+				},
+			},
+			&schema.BodySchema{Attributes: map[string]*schema.AttributeSchema{
+				"name": &schema.AttributeSchema{
+					Description: lang.MarkupContent{
+						Value: "name of the module",
+						Kind:  lang.PlainTextKind,
+					},
+					Expr: schema.ExprConstraints{schema.LiteralTypeExpr{cty.String}},
+				},
+				"id": &schema.AttributeSchema{
+					Description: lang.MarkupContent{
+						Value: "id of the module",
+						Kind:  lang.PlainTextKind,
+					},
+					Expr: schema.ExprConstraints{schema.LiteralTypeExpr{cty.Number}},
+				},
+			}},
+		},
+	}
+
+	for i, tc := range testCases {
+		t.Run(fmt.Sprintf("%d-%s", i, tc.name), func(t *testing.T) {
+			actualSchema, err := SchemaForVariables(tc.variables)
+
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			diff := cmp.Diff(tc.expectedSchema, actualSchema, ctydebug.CmpOptions)
+			if diff != "" {
+				t.Fatalf("unexpected schema %s", diff)
+			}
+		})
+	}
+}