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compat_shim.go
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compat_shim.go
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package configs
import (
"github.com/hashicorp/hcl/v2"
"github.com/hashicorp/hcl/v2/hclsyntax"
"github.com/zclconf/go-cty/cty"
)
// -------------------------------------------------------------------------
// Functions in this file are compatibility shims intended to ease conversion
// from the old configuration loader. Any use of these functions that makes
// a change should generate a deprecation warning explaining to the user how
// to update their code for new patterns.
//
// Shims are particularly important for any patterns that have been widely
// documented in books, tutorials, etc. Users will still be starting from
// these examples and we want to help them adopt the latest patterns rather
// than leave them stranded.
// -------------------------------------------------------------------------
// shimTraversalInString takes any arbitrary expression and checks if it is
// a quoted string in the native syntax. If it _is_, then it is parsed as a
// traversal and re-wrapped into a synthetic traversal expression and a
// warning is generated. Otherwise, the given expression is just returned
// verbatim.
//
// This function has no effect on expressions from the JSON syntax, since
// traversals in strings are the required pattern in that syntax.
//
// If wantKeyword is set, the generated warning diagnostic will talk about
// keywords rather than references. The behavior is otherwise unchanged, and
// the caller remains responsible for checking that the result is indeed
// a keyword, e.g. using hcl.ExprAsKeyword.
func shimTraversalInString(expr hcl.Expression, wantKeyword bool) (hcl.Expression, hcl.Diagnostics) {
// ObjectConsKeyExpr is a special wrapper type used for keys on object
// constructors to deal with the fact that naked identifiers are normally
// handled as "bareword" strings rather than as variable references. Since
// we know we're interpreting as a traversal anyway (and thus it won't
// matter whether it's a string or an identifier) we can safely just unwrap
// here and then process whatever we find inside as normal.
if ocke, ok := expr.(*hclsyntax.ObjectConsKeyExpr); ok {
expr = ocke.Wrapped
}
if !exprIsNativeQuotedString(expr) {
return expr, nil
}
strVal, diags := expr.Value(nil)
if diags.HasErrors() || strVal.IsNull() || !strVal.IsKnown() {
// Since we're not even able to attempt a shim here, we'll discard
// the diagnostics we saw so far and let the caller's own error
// handling take care of reporting the invalid expression.
return expr, nil
}
// The position handling here isn't _quite_ right because it won't
// take into account any escape sequences in the literal string, but
// it should be close enough for any error reporting to make sense.
srcRange := expr.Range()
startPos := srcRange.Start // copy
startPos.Column++ // skip initial quote
startPos.Byte++ // skip initial quote
traversal, tDiags := hclsyntax.ParseTraversalAbs(
[]byte(strVal.AsString()),
srcRange.Filename,
startPos,
)
diags = append(diags, tDiags...)
if wantKeyword {
diags = append(diags, &hcl.Diagnostic{
Severity: hcl.DiagWarning,
Summary: "Quoted keywords are deprecated",
Detail: "In this context, keywords are expected literally rather than in quotes. Terraform 0.11 and earlier required quotes, but quoted keywords are now deprecated and will be removed in a future version of Terraform. Remove the quotes surrounding this keyword to silence this warning.",
Subject: &srcRange,
})
} else {
diags = append(diags, &hcl.Diagnostic{
Severity: hcl.DiagWarning,
Summary: "Quoted references are deprecated",
Detail: "In this context, references are expected literally rather than in quotes. Terraform 0.11 and earlier required quotes, but quoted references are now deprecated and will be removed in a future version of Terraform. Remove the quotes surrounding this reference to silence this warning.",
Subject: &srcRange,
})
}
return &hclsyntax.ScopeTraversalExpr{
Traversal: traversal,
SrcRange: srcRange,
}, diags
}
// shimIsIgnoreChangesStar returns true if the given expression seems to be
// a string literal whose value is "*". This is used to support a legacy
// form of ignore_changes = all .
//
// This function does not itself emit any diagnostics, so it's the caller's
// responsibility to emit a warning diagnostic when this function returns true.
func shimIsIgnoreChangesStar(expr hcl.Expression) bool {
val, valDiags := expr.Value(nil)
if valDiags.HasErrors() {
return false
}
if val.Type() != cty.String || val.IsNull() || !val.IsKnown() {
return false
}
return val.AsString() == "*"
}
// warnForDeprecatedInterpolations returns warning diagnostics if the given
// body can be proven to contain attributes whose expressions are native
// syntax expressions consisting entirely of a single template interpolation,
// which is a deprecated way to include a non-literal value in configuration.
//
// This is a best-effort sort of thing which relies on the physical HCL native
// syntax AST, so it might not catch everything. The main goal is to catch the
// "obvious" cases in order to help spread awareness that this old form is
// deprecated, when folks copy it from older examples they've found on the
// internet that were written for Terraform 0.11 or earlier.
func warnForDeprecatedInterpolationsInBody(body hcl.Body) hcl.Diagnostics {
var diags hcl.Diagnostics
nativeBody, ok := body.(*hclsyntax.Body)
if !ok {
// If it's not native syntax then we've nothing to do here.
return diags
}
for _, attr := range nativeBody.Attributes {
moreDiags := warnForDeprecatedInterpolationsInExpr(attr.Expr)
diags = append(diags, moreDiags...)
}
for _, block := range nativeBody.Blocks {
// We'll also go hunting in nested blocks
moreDiags := warnForDeprecatedInterpolationsInBody(block.Body)
diags = append(diags, moreDiags...)
}
return diags
}
func warnForDeprecatedInterpolationsInExpr(expr hcl.Expression) hcl.Diagnostics {
var diags hcl.Diagnostics
if _, ok := expr.(*hclsyntax.TemplateWrapExpr); !ok {
// We're only interested in TemplateWrapExpr, because that's how
// the HCL native syntax parser represents the case of a template
// that consists entirely of a single interpolation expression, which
// is therefore subject to the special case of passing through the
// inner value without conversion to string.
return diags
}
diags = append(diags, &hcl.Diagnostic{
Severity: hcl.DiagWarning,
Summary: "Interpolation-only expressions are deprecated",
Detail: "Terraform 0.11 and earlier required all non-constant expressions to be provided via interpolation syntax, but this pattern is now deprecated. To silence this warning, remove the \"${ sequence from the start and the }\" sequence from the end of this expression, leaving just the inner expression.\n\nTemplate interpolation syntax is still used to construct strings from expressions when the template includes multiple interpolation sequences or a mixture of literal strings and interpolations. This deprecation applies only to templates that consist entirely of a single interpolation sequence.",
Subject: expr.Range().Ptr(),
})
return diags
}