opentofu/terraform/eval_count.go
Martin Atkins 39e609d5fd vendor: switch to HCL 2.0 in the HCL repository
Previously we were using the experimental HCL 2 repository, but now we'll
shift over to the v2 import path within the main HCL repository as part of
actually releasing HCL 2.0 as stable.

This is a mechanical search/replace to the new import paths. It also
switches to the v2.0.0 release of HCL, which includes some new code that
Terraform didn't previously have but should not change any behavior that
matters for Terraform's purposes.

For the moment the experimental HCL2 repository is still an indirect
dependency via terraform-config-inspect, so it remains in our go.sum and
vendor directories for the moment. Because terraform-config-inspect uses
a much smaller subset of the HCL2 functionality, this does still manage
to prune the vendor directory a little. A subsequent release of
terraform-config-inspect should allow us to completely remove that old
repository in a future commit.
2019-10-02 15:10:21 -07:00

121 lines
4.6 KiB
Go

package terraform
import (
"fmt"
"log"
"github.com/hashicorp/hcl/v2"
"github.com/hashicorp/terraform/addrs"
"github.com/hashicorp/terraform/tfdiags"
"github.com/zclconf/go-cty/cty"
"github.com/zclconf/go-cty/cty/gocty"
)
// evaluateResourceCountExpression is our standard mechanism for interpreting an
// expression given for a "count" argument on a resource. This should be called
// from the DynamicExpand of a node representing a resource in order to
// determine the final count value.
//
// If the result is zero or positive and no error diagnostics are returned, then
// the result is the literal count value to use.
//
// If the result is -1, this indicates that the given expression is nil and so
// the "count" behavior should not be enabled for this resource at all.
//
// If error diagnostics are returned then the result is always the meaningless
// placeholder value -1.
func evaluateResourceCountExpression(expr hcl.Expression, ctx EvalContext) (int, tfdiags.Diagnostics) {
count, known, diags := evaluateResourceCountExpressionKnown(expr, ctx)
if !known {
// Currently this is a rather bad outcome from a UX standpoint, since we have
// no real mechanism to deal with this situation and all we can do is produce
// an error message.
// FIXME: In future, implement a built-in mechanism for deferring changes that
// can't yet be predicted, and use it to guide the user through several
// plan/apply steps until the desired configuration is eventually reached.
diags = diags.Append(&hcl.Diagnostic{
Severity: hcl.DiagError,
Summary: "Invalid count argument",
Detail: `The "count" value depends on resource attributes that cannot be determined until apply, so Terraform cannot predict how many instances will be created. To work around this, use the -target argument to first apply only the resources that the count depends on.`,
Subject: expr.Range().Ptr(),
})
}
return count, diags
}
// evaluateResourceCountExpressionKnown is like evaluateResourceCountExpression
// except that it handles an unknown result by returning count = 0 and
// a known = false, rather than by reporting the unknown value as an error
// diagnostic.
func evaluateResourceCountExpressionKnown(expr hcl.Expression, ctx EvalContext) (count int, known bool, diags tfdiags.Diagnostics) {
if expr == nil {
return -1, true, nil
}
countVal, countDiags := ctx.EvaluateExpr(expr, cty.Number, nil)
diags = diags.Append(countDiags)
if diags.HasErrors() {
return -1, true, diags
}
switch {
case countVal.IsNull():
diags = diags.Append(&hcl.Diagnostic{
Severity: hcl.DiagError,
Summary: "Invalid count argument",
Detail: `The given "count" argument value is null. An integer is required.`,
Subject: expr.Range().Ptr(),
})
return -1, true, diags
case !countVal.IsKnown():
return 0, false, diags
}
err := gocty.FromCtyValue(countVal, &count)
if err != nil {
diags = diags.Append(&hcl.Diagnostic{
Severity: hcl.DiagError,
Summary: "Invalid count argument",
Detail: fmt.Sprintf(`The given "count" argument value is unsuitable: %s.`, err),
Subject: expr.Range().Ptr(),
})
return -1, true, diags
}
if count < 0 {
diags = diags.Append(&hcl.Diagnostic{
Severity: hcl.DiagError,
Summary: "Invalid count argument",
Detail: `The given "count" argument value is unsuitable: negative numbers are not supported.`,
Subject: expr.Range().Ptr(),
})
return -1, true, diags
}
return count, true, diags
}
// fixResourceCountSetTransition is a helper function to fix up the state when a
// resource transitions its "count" from being set to unset or vice-versa,
// treating a 0-key and a no-key instance as aliases for one another across
// the transition.
//
// The correct time to call this function is in the DynamicExpand method for
// a node representing a resource, just after evaluating the count with
// evaluateResourceCountExpression, and before any other analysis of the
// state such as orphan detection.
//
// This function calls methods on the given EvalContext to update the current
// state in-place, if necessary. It is a no-op if there is no count transition
// taking place.
//
// Since the state is modified in-place, this function must take a writer lock
// on the state. The caller must therefore not also be holding a state lock,
// or this function will block forever awaiting the lock.
func fixResourceCountSetTransition(ctx EvalContext, addr addrs.AbsResource, countEnabled bool) {
state := ctx.State()
changed := state.MaybeFixUpResourceInstanceAddressForCount(addr, countEnabled)
if changed {
log.Printf("[TRACE] renamed first %s instance in transient state due to count argument change", addr)
}
}