hclsyntax: maintain marks from unknown values

Do not discard marks from unknown values when processing string
templates.

hclsyntax/expression_template.go

@@ -48,6 +48,12 @@ func (e *TemplateExpr) Value(ctx *hcl.EvalContext) (cty.Value, hcl.Diagnostics)
  continue
  }
 
+ // Unmark the part and merge its marks into the set
+ unmarkedVal, partMarks := partVal.Unmark()
+ for k, v := range partMarks {
+ marks[k] = v
+ }
+
  if !partVal.IsKnown() {
  // If any part is unknown then the result as a whole must be
  // unknown too. We'll keep on processing the rest of the parts
@@ -57,7 +63,7 @@ func (e *TemplateExpr) Value(ctx *hcl.EvalContext) (cty.Value, hcl.Diagnostics)
  continue
  }
 
- strVal, err := convert.Convert(partVal, cty.String)
+ strVal, err := convert.Convert(unmarkedVal, cty.String)
  if err != nil {
  diags = append(diags, &hcl.Diagnostic{
  Severity: hcl.DiagError,
@@ -74,13 +80,7 @@ func (e *TemplateExpr) Value(ctx *hcl.EvalContext) (cty.Value, hcl.Diagnostics)
  continue
  }
 
- // Unmark the part and merge its marks into the set
- unmarked, partMarks := strVal.Unmark()
- for k, v := range partMarks {
- marks[k] = v
- }
-
- buf.WriteString(unmarked.AsString())
+ buf.WriteString(strVal.AsString())
  }
 
  var ret cty.Value

hclsyntax/expression_template_test.go

@@ -358,6 +358,16 @@ trim`,
  cty.StringVal("foobarbaz").WithMarks(cty.NewValueMarks("x", "y", "z")),
  0,
  },
+ { // marks from unknown values are maintained
+ `test_${target}`,
+ &hcl.EvalContext{
+ Variables: map[string]cty.Value{
+ "target": cty.UnknownVal(cty.String).Mark("sensitive"),
+ },
+ },
+ cty.UnknownVal(cty.String).Mark("sensitive"),
+ 0,
+ },
  }
 
  for _, test := range tests {