hashicorp/terraform · error

invalid tfvars syntax

Error message

invalid tfvars syntax: %s

What it means

decode_tfvars feeds the input string to hclsyntax.ParseConfig. If the HCL parser reports errors (unterminated strings, invalid tokens, malformed expressions), they are wrapped into this message. This is a genuine user-facing error: the supplied string is not valid HCL/terraform-tfvars syntax.

Solutions

1. Read the wrapped HCL diagnostic to locate the exact offset/token causing the parse failure and fix it
2. Validate the string parses as HCL before calling (run it through hclsyntax.ParseConfig, or terraform fmt -check)
3. If the input is a file, run terraform fmt on it first to surface and auto-fix common syntax issues

Example fix

// before
decode_tfvars("name = 'broken")
// after
decode_tfvars("name = \"fixed\"")

// Pre-parse the tfvars string with HCL before handing it to decode_tfvars.
// In Go:
f, diags := hclsyntax.ParseConfig([]byte(src), "check.tfvars", hcl.InitialPos)
if diags.HasErrors() {
    // surface diags to the user instead of calling decode_tfvars
    return diags
}
// In HCL, validate the source file first:
// validate that file(var.path) is non-empty and well-formed via a fmt check in CI

When it happens

Trigger: decode_tfvars("name = 'broken") with an unterminated string; decode_tfvars("a = =") with an invalid expression token; any malformed tfvars content passed as the single argument.

Common situations: Reading a .tfvars file with file() that contains a typo or unbalanced quotes; programmatically building a tfvars string without escaping embedded quotes; copy-pasting partial config into decode_tfvars.

Related errors

• invalid expression for variable
• cannot decode tfvars from a null value
• invalid tfvars content
• all arguments must have the same type
• argument must be a list or tuple

AI-assisted analysis of hashicorp/terraform@d32a084675 (2026-08-11). Data as JSON: /api/errors/b2f382c1720897a2. Report an issue: GitHub.

Appendix: source

Thrown at internal/builtin/providers/terraform/functions.go:121

		// type, since it will be an object type decided based on which
		// arguments and values we find in the string.
		return cty.DynamicVal, nil
	}

	// If we get here then we know that:
	// - there's exactly one element in args
	// - it's a string
	// - it is known and non-null
	// So therefore the following is guaranteed to succeed.
	src := []byte(args[0].AsString())

	// As usual when we wrap HCL stuff up in functions, we end up needing to
	// stuff HCL diagnostics into plain string error messages. This produces
	// a non-ideal result but is still better than hiding the HCL-provided
	// diagnosis altogether.
	f, hclDiags := hclsyntax.ParseConfig(src, "<decode_tfvars argument>", hcl.InitialPos)
	if hclDiags.HasErrors() {
		return cty.NilVal, fmt.Errorf("invalid tfvars syntax: %s", hclDiags.Error())
	}
	attrs, hclDiags := f.Body.JustAttributes()
	if hclDiags.HasErrors() {
		return cty.NilVal, fmt.Errorf("invalid tfvars content: %s", hclDiags.Error())
	}
	retAttrs := make(map[string]cty.Value, len(attrs))
	for name, attr := range attrs {
		// Evaluating the expression with no EvalContext achieves the same
		// interpretation as Terraform CLI makes of .tfvars files, rejecting
		// any function calls or references to symbols.
		v, hclDiags := attr.Expr.Value(nil)
		if hclDiags.HasErrors() {
			return cty.NilVal, fmt.Errorf("invalid expression for variable %q: %s", name, hclDiags.Error())
		}
		retAttrs[name] = v
	}

	return cty.ObjectVal(retAttrs), nil

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