opentofu/terraform/eval_count.go
Martin Atkins a3403f2766 terraform: Ugly huge change to weave in new State and Plan types
Due to how often the state and plan types are referenced throughout
Terraform, there isn't a great way to switch them out gradually. As a
consequence, this huge commit gets us from the old world to a _compilable_
new world, but still has a large number of known test failures due to
key functionality being stubbed out.

The stubs here are for anything that interacts with providers, since we
now need to do the follow-up work to similarly replace the old
terraform.ResourceProvider interface with its replacement in the new
"providers" package. That work, along with work to fix the remaining
failing tests, will follow in subsequent commits.

The aim here was to replace all references to terraform.State and its
downstream types with states.State, terraform.Plan with plans.Plan,
state.State with statemgr.State, and switch to the new implementations of
the state and plan file formats. However, due to the number of times those
types are used, this also ended up affecting numerous other parts of core
such as terraform.Hook, the backend.Backend interface, and most of the CLI
commands.

Just as with 5861dbf3fc49b19587a31816eb06f511ab861bb4 before, I apologize
in advance to the person who inevitably just found this huge commit while
spelunking through the commit history.
2018-10-16 19:11:09 -07:00

123 lines
4.8 KiB
Go

package terraform
import (
"fmt"
"log"
"github.com/hashicorp/hcl2/hcl"
"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, except in one case: if the count expression evaluates
// to an unknown number value then the result is zero, allowing this situation
// to be treated by the caller as special if needed. For example, an early
// graph walk may wish to just silently skip resources with unknown counts
// to allow them to be dealt with in a later graph walk where more information
// is available.
func evaluateResourceCountExpression(expr hcl.Expression, ctx EvalContext) (int, tfdiags.Diagnostics) {
if expr == nil {
return -1, nil
}
var diags tfdiags.Diagnostics
var count int
countVal, countDiags := ctx.EvaluateExpr(expr, cty.Number, nil)
diags = diags.Append(countDiags)
if diags.HasErrors() {
return -1, 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, diags
case !countVal.IsKnown():
// 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(),
})
// We return zero+errors in this one case to allow callers to handle
// an unknown count as special. This is rarely necessary, but is used
// by the validate walk in particular so that it can just skip
// validation in this case, assuming a later walk will take care of it.
return 0, 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, 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, diags
}
return count, 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.Resource, countEnabled bool) {
path := ctx.Path()
state := ctx.State()
changed := state.MaybeFixUpResourceInstanceAddressForCount(addr.Absolute(path), countEnabled)
if changed {
log.Printf("[TRACE] renamed first %s instance in transient state due to count argument change", addr)
}
}