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Sarah/validate backend blocks #38021

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930ca48
feat: Make validate command detect when an unknown backend type is in…
SarahFrench Dec 5, 2025
985430c
feat: Make validate command detect when the backend configuration doe…
SarahFrench Dec 5, 2025
1292a4d
fix: Stop suppressing the Required:true parts of the backend schema w…
SarahFrench Dec 11, 2025
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52 changes: 52 additions & 0 deletions internal/command/validate.go
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Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,10 @@ import (
"path/filepath"
"strings"

"github.com/hashicorp/hcl/v2"
"github.com/hashicorp/hcl/v2/hcldec"
"github.com/hashicorp/terraform/internal/addrs"
backendInit "github.com/hashicorp/terraform/internal/backend/init"
"github.com/hashicorp/terraform/internal/command/arguments"
"github.com/hashicorp/terraform/internal/command/views"
"github.com/hashicorp/terraform/internal/configs"
Expand Down Expand Up @@ -87,6 +90,13 @@ func (c *ValidateCommand) validate(dir string) tfdiags.Diagnostics {

diags = diags.Append(c.validateConfig(cfg))

// Validation of backend block, if present
// Backend blocks live outside the Terraform graph so we have to do this separately.
backend := cfg.Module.Backend
if backend != nil {
diags = diags.Append(c.validateBackend(backend))
}

// Unless excluded, we'll also do a quick validation of the Terraform test files. These live
// outside the Terraform graph so we have to do this separately.
if !c.ParsedArgs.NoTests {
Expand Down Expand Up @@ -157,6 +167,48 @@ func (c *ValidateCommand) validateTestFiles(cfg *configs.Config) tfdiags.Diagnos
return diags
}

// We validate the backend in an offline manner, so we use PrepareConfig to validate the configuration (and ENVs present),
// but we never use the Configure method, as that will interact with third-party systems.
//
// The code in this method is very similar to the `backendInitFromConfig` method, expect it doesn't configure the backend.
func (c *ValidateCommand) validateBackend(cfg *configs.Backend) tfdiags.Diagnostics {
var diags tfdiags.Diagnostics

bf := backendInit.Backend(cfg.Type)
if bf == nil {
detail := fmt.Sprintf("There is no backend type named %q.", cfg.Type)
if msg, removed := backendInit.RemovedBackends[cfg.Type]; removed {
detail = msg
}

diags = diags.Append(&hcl.Diagnostic{
Severity: hcl.DiagError,
Summary: "Unsupported backend type",
Detail: detail,
Subject: &cfg.TypeRange,
})
return diags
}

b := bf()
backendSchema := b.ConfigSchema()

decSpec := backendSchema.DecoderSpec()
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@SarahFrench SarahFrench Dec 19, 2025

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Need test coverage of detecting a missing required attr, and need to confirm there aren't any quirks with remote-state backends that affect the assumptions here.

configVal, hclDiags := hcldec.Decode(cfg.Config, decSpec, nil)
diags = diags.Append(hclDiags)
if hclDiags.HasErrors() {
return diags
}

_, validateDiags := b.PrepareConfig(configVal)
diags = diags.Append(validateDiags)
if validateDiags.HasErrors() {
return diags
}

return diags
}

func (c *ValidateCommand) Synopsis() string {
return "Check whether the configuration is valid"
}
Expand Down
34 changes: 16 additions & 18 deletions internal/command/validate_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -547,33 +547,31 @@ func TestValidate_backendBlocks(t *testing.T) {
}
})

// TODO: Should this validation be added?
t.Run("NOT invalid when the backend type is unknown", func(t *testing.T) {
t.Run("invalid when the backend type is unknown", func(t *testing.T) {
output, code := setupTest(t, "invalid-backend-configuration/unknown-backend-type")
if code != 0 {
t.Fatalf("expected a successful exit code %d\n\n%s", code, output.Stderr())
if code != 1 {
t.Fatalf("expected an unsuccessful exit code %d\n\n%s", code, output.Stderr())
}
expectedMsg := "Success! The configuration is valid."
if !strings.Contains(output.Stdout(), expectedMsg) {
t.Fatalf("unexpected output content: wanted %q, got: %s",
expectedMsg,
output.Stdout(),
expectedErr := "Error: Unsupported backend type"
if !strings.Contains(output.Stderr(), expectedErr) {
t.Fatalf("unexpected error content: wanted %q, got: %s",
expectedErr,
output.Stderr(),
)
}
})

// Backend blocks aren't validated using their schemas currently.
// TODO: Should this validation be added?
t.Run("NOT invalid when there's an unknown attribute present", func(t *testing.T) {
t.Run("invalid when there's an unknown attribute present", func(t *testing.T) {
output, code := setupTest(t, "invalid-backend-configuration/unknown-attr")
if code != 0 {
t.Fatalf("expected a successful exit code %d\n\n%s", code, output.Stderr())
if code != 1 {
t.Fatalf("expected an unsuccessful exit code %d\n\n%s", code, output.Stdout())
}
expectedMsg := "Success! The configuration is valid."
if !strings.Contains(output.Stdout(), expectedMsg) {
t.Fatalf("unexpected output content: wanted %q, got: %s",
expectedMsg,
output.Stdout(),
expectedErr := "Error: Unsupported argument"
if !strings.Contains(output.Stderr(), expectedErr) {
t.Fatalf("unexpected error content: wanted %q, got: %s",
expectedErr,
output.Stderr(),
)
}
})
Expand Down
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