hashicorp/terraform · error

Only .tf, .tfvars, and .tftest.hcl files can be processed…

Error message

Only .tf, .tfvars, and .tftest.hcl files can be processed with terraform fmt

What it means

Thrown by `terraform fmt` when a path passed on the command line refers to a regular file whose name does not end in one of the supported extensions (.tf, .tfvars, .tftest.hcl). The command iterates fmtSupportedExts; if none match, fmtd stays false and the file is rejected. This guards the formatter from operating on non-HCL files where formatting would be meaningless or destructive.

Solutions

1. Rename or restrict the argument to a file with a .tf, .tfvars, or .tftest.hcl extension.
2. If formatting a directory, pass the directory path instead of individual non-HCL files so unsupported files are skipped automatically.
3. Convert JSON-syntax config (.tf.json) to native HCL (.tf) before formatting, since fmt does not support JSON syntax.

Example fix

// before
$ terraform fmt main.tf.json
// after
$ terraform fmt main.tf

// Before calling fmt on a path, verify the extension is supported.
func isFmtSupported(path string) bool {
    for _, ext := range []string{".tf", ".tfvars", ".tftest.hcl"} {
        if strings.HasSuffix(path, ext) {
            return true
        }
    }
    return false
}
// usage:
// if !isFmtSupported(p) { return fmt.Errorf("skip: %s unsupported", p) }

When it happens

Trigger: Running `terraform fmt main.tf.json`, `terraform fmt README.md`, `terraform fmt script.sh`, or passing any file with an unsupported extension directly (not a directory). Directory traversal (processDir) skips non-matching files silently, so this only fires for explicit file arguments.

Common situations: Passing a JSON-syntax Terraform file (.tf.json) which is NOT supported by fmt; passing a .sh hook script; mistyping a filename; attempting to format a generated file like .terraform.lock.hcl.

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AI-assisted analysis of hashicorp/terraform@d32a084675 (2026-08-11). Data as JSON: /api/errors/a668726d324c91ec. Report an issue: GitHub.

Appendix: source

Thrown at internal/command/fmt.go:163

						// so we'll need to simplify here.
						diags = diags.Append(fmt.Errorf("Failed to read file %s", path))
						continue
					}

					fileDiags := c.processFile(c.normalizePath(path), f, stdout, false)
					diags = diags.Append(fileDiags)
					f.Close()

					// Take note that we processed the file.
					fmtd = true

					// Don't check the remaining extensions.
					break
				}
			}

			if !fmtd {
				diags = diags.Append(fmt.Errorf("Only .tf, .tfvars, and .tftest.hcl files can be processed with terraform fmt"))
				continue
			}
		}
	}

	return diags
}

func (c *FmtCommand) processFile(path string, r io.Reader, w io.Writer, isStdout bool) tfdiags.Diagnostics {
	var diags tfdiags.Diagnostics

	log.Printf("[TRACE] terraform fmt: Formatting %s", path)

	src, err := io.ReadAll(r)
	if err != nil {
		diags = diags.Append(fmt.Errorf("Failed to read %s", path))
		return diags
	}

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