Add environment variable for disabling YAML type checking (#634)

This adds an option to the YAML runtime to disable the type checking.
This is controlled by the `PULUMI_YAML_DISABLE_TYPE_CHECKING`
environment variable.

This is useful for tests where we need to test type mismatches which
could happen in other languages, like Python or Typescript.

Can use some guidance on how to add tests here.

Required for
pulumi/pulumi-terraform-bridge#2418

pkg/pulumiyaml/analyser.go

@@ -4,13 +4,15 @@ package pulumiyaml
 
 import (
 	"fmt"
+	"os"
 	"reflect"
 	"strconv"
 	"strings"
 
 	"github.com/hashicorp/hcl/v2"
 	"github.com/pulumi/pulumi/pkg/v3/codegen"
 	"github.com/pulumi/pulumi/pkg/v3/codegen/schema"
+	"github.com/pulumi/pulumi/sdk/v3/go/common/util/cmdutil"
 
 	"github.com/pulumi/pulumi-yaml/pkg/pulumiyaml/ast"
 	ctypes "github.com/pulumi/pulumi-yaml/pkg/pulumiyaml/config"
@@ -532,9 +534,20 @@ func hasValidEnumValue(from ast.Expr, to []*schema.Enum) *notAssignable {
 	}
 }
 
+var disableTypeChecking = cmdutil.IsTruthy(os.Getenv("PULUMI_DEBUG_YAML_DISABLE_TYPE_CHECKING"))
+
 // Provides an appropriate diagnostic message if it is illegal to assign `from`
 // to `to`.
 func (tc *typeCache) assertTypeAssignable(ctx *evalContext, from ast.Expr, to schema.Type) {
+	if disableTypeChecking {
+		ctx.addWarnDiag(
+			from.Syntax().Syntax().Range(),
+			"Running with type checking disabled. This is not recommended for production use.",
+			"This is a test feature and should not be used in production. Unexpected behavior may occur.",
+		)
+		return
+	}
+
 	if to == nil {
 		return
 	}