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configs: Generalize "VariableValidation" as "CheckRule" 

This construct of a block containing a condition and an error message will
be useful for other sorts of blocks defining expectations or contracts, so
we'll give it a more generic name in anticipation of it being used in
other situations.
This commit is contained in:
Martin Atkins 2020-11-20 14:05:13 -08:00 committed by Alisdair McDiarmid
parent 0900c7e0bb
commit 4f41a0a1fe
3 changed files with 161 additions and 133 deletions
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152
internal/configs/checks.go Normal file
View File

@ -0,0 +1,152 @@
package configs
import (
"fmt"
"unicode"
"github.com/hashicorp/hcl/v2"
"github.com/hashicorp/hcl/v2/gohcl"
)
// CheckRule represents a configuration-defined validation rule, precondition,
// or postcondition. Blocks of this sort can appear in a few different places
// in configuration, including "validation" blocks for variables,
// and "precondition" and "postcondition" blocks for resources.
type CheckRule struct {
// Condition is an expression that must evaluate to true if the condition
// holds or false if it does not. If the expression produces an error then
// that's considered to be a bug in the module defining the check.
//
// The available variables in a condition expression vary depending on what
// a check is attached to. For example, validation rules attached to
// input variables can only refer to the variable that is being validated.
Condition hcl.Expression
// ErrorMessage is one or more full sentences, which would need to be in
// English for consistency with the rest of the error message output but
// can in practice be in any language as long as it ends with a period.
// The message should describe what is required for the condition to return
// true in a way that would make sense to a caller of the module.
ErrorMessage string
DeclRange hcl.Range
}
// decodeCheckRuleBlock decodes the contents of the given block as a check rule.
//
// Unlike most of our "decode..." functions, this one can be applied to blocks
// of various types as long as their body structures are "check-shaped". The
// function takes the containing block only because some error messages will
// refer to its location, and the returned object's DeclRange will be the
// block's header.
func decodeCheckRuleBlock(block *hcl.Block, override bool) (*CheckRule, hcl.Diagnostics) {
var diags hcl.Diagnostics
cr := &CheckRule{
DeclRange: block.DefRange,
}
if override {
// For now we'll just forbid overriding check blocks, to simplify
// the initial design. If we can find a clear use-case for overriding
// checks in override files and there's a way to define it that
// isn't confusing then we could relax this.
diags = diags.Append(&hcl.Diagnostic{
Severity: hcl.DiagError,
Summary: fmt.Sprintf("Can't override %s blocks", block.Type),
Detail: fmt.Sprintf("Override files cannot override %q blocks.", block.Type),
Subject: cr.DeclRange.Ptr(),
})
return cr, diags
}
content, moreDiags := block.Body.Content(checkRuleBlockSchema)
diags = append(diags, moreDiags...)
if attr, exists := content.Attributes["condition"]; exists {
cr.Condition = attr.Expr
}
if attr, exists := content.Attributes["error_message"]; exists {
moreDiags := gohcl.DecodeExpression(attr.Expr, nil, &cr.ErrorMessage)
diags = append(diags, moreDiags...)
if !moreDiags.HasErrors() {
const errSummary = "Invalid validation error message"
switch {
case cr.ErrorMessage == "":
diags = diags.Append(&hcl.Diagnostic{
Severity: hcl.DiagError,
Summary: errSummary,
Detail: "An empty string is not a valid nor useful error message.",
Subject: attr.Expr.Range().Ptr(),
})
case !looksLikeSentences(cr.ErrorMessage):
// Because we're going to include this string verbatim as part
// of a bigger error message written in our usual style in
// English, we'll require the given error message to conform
// to that. We might relax this in future if e.g. we start
// presenting these error messages in a different way, or if
// Terraform starts supporting producing error messages in
// other human languages, etc.
// For pragmatism we also allow sentences ending with
// exclamation points, but we don't mention it explicitly here
// because that's not really consistent with the Terraform UI
// writing style.
diags = diags.Append(&hcl.Diagnostic{
Severity: hcl.DiagError,
Summary: errSummary,
Detail: "The validation error message must be at least one full sentence starting with an uppercase letter and ending with a period or question mark.\n\nYour given message will be included as part of a larger Terraform error message, written as English prose. For broadly-shared modules we suggest using a similar writing style so that the overall result will be consistent.",
Subject: attr.Expr.Range().Ptr(),
})
}
}
}
return cr, diags
}
// looksLikeSentence is a simple heuristic that encourages writing error
// messages that will be presentable when included as part of a larger
// Terraform error diagnostic whose other text is written in the Terraform
// UI writing style.
//
// This is intentionally not a very strong validation since we're assuming
// that module authors want to write good messages and might just need a nudge
// about Terraform's specific style, rather than that they are going to try
// to work around these rules to write a lower-quality message.
func looksLikeSentences(s string) bool {
if len(s) < 1 {
return false
}
runes := []rune(s) // HCL guarantees that all strings are valid UTF-8
first := runes[0]
last := runes[len(runes)-1]
// If the first rune is a letter then it must be an uppercase letter.
// (This will only see the first rune in a multi-rune combining sequence,
// but the first rune is generally the letter if any are, and if not then
// we'll just ignore it because we're primarily expecting English messages
// right now anyway, for consistency with all of Terraform's other output.)
if unicode.IsLetter(first) && !unicode.IsUpper(first) {
return false
}
// The string must be at least one full sentence, which implies having
// sentence-ending punctuation.
// (This assumes that if a sentence ends with quotes then the period
// will be outside the quotes, which is consistent with Terraform's UI
// writing style.)
return last == '.' || last == '?' || last == '!'
}
var checkRuleBlockSchema = &hcl.BodySchema{
Attributes: []hcl.AttributeSchema{
{
Name: "condition",
Required: true,
},
{
Name: "error_message",
Required: true,
},
},
}

140
internal/configs/named_values.go
View File

@ -2,7 +2,6 @@ package configs
import (
"fmt"
"unicode"
"github.com/hashicorp/hcl/v2"
"github.com/hashicorp/hcl/v2/gohcl"
@ -30,7 +29,7 @@ type Variable struct {
ConstraintType cty.Type
ParsingMode VariableParsingMode
Validations []*VariableValidation
Validations []*CheckRule
Sensitive bool
DescriptionSet bool
@ -308,53 +307,12 @@ func (m VariableParsingMode) Parse(name, value string) (cty.Value, hcl.Diagnosti
}
}
// VariableValidation represents a configuration-defined validation rule
// for a particular input variable, given as a "validation" block inside
// a "variable" block.
type VariableValidation struct {
// Condition is an expression that refers to the variable being tested
// and contains no other references. The expression must return true
// to indicate that the value is valid or false to indicate that it is
// invalid. If the expression produces an error, that's considered a bug
// in the module defining the validation rule, not an error in the caller.
Condition hcl.Expression
// ErrorMessage is one or more full sentences, which would need to be in
// English for consistency with the rest of the error message output but
// can in practice be in any language as long as it ends with a period.
// The message should describe what is required for the condition to return
// true in a way that would make sense to a caller of the module.
ErrorMessage string
DeclRange hcl.Range
}
func decodeVariableValidationBlock(varName string, block *hcl.Block, override bool) (*VariableValidation, hcl.Diagnostics) {
var diags hcl.Diagnostics
vv := &VariableValidation{
DeclRange: block.DefRange,
}
if override {
// For now we'll just forbid overriding validation blocks, to simplify
// the initial design. If we can find a clear use-case for overriding
// validations in override files and there's a way to define it that
// isn't confusing then we could relax this.
diags = diags.Append(&hcl.Diagnostic{
Severity: hcl.DiagError,
Summary: "Can't override variable validation rules",
Detail: "Variable \"validation\" blocks cannot be used in override files.",
Subject: vv.DeclRange.Ptr(),
})
return vv, diags
}
content, moreDiags := block.Body.Content(variableValidationBlockSchema)
diags = append(diags, moreDiags...)
if attr, exists := content.Attributes["condition"]; exists {
vv.Condition = attr.Expr
// decodeVariableValidationBlock is a wrapper around decodeCheckRuleBlock
// that imposes the additional rule that the condition expression can refer
// only to an input variable of the given name.
func decodeVariableValidationBlock(varName string, block *hcl.Block, override bool) (*CheckRule, hcl.Diagnostics) {
vv, diags := decodeCheckRuleBlock(block, override)
if vv.Condition != nil {
// The validation condition can only refer to the variable itself,
// to ensure that the variable declaration can't create additional
// edges in the dependency graph.
@ -382,83 +340,14 @@ func decodeVariableValidationBlock(varName string, block *hcl.Block, override bo
Severity: hcl.DiagError,
Summary: "Invalid variable validation condition",
Detail: fmt.Sprintf("The condition for variable %q must refer to var.%s in order to test incoming values.", varName, varName),
Subject: attr.Expr.Range().Ptr(),
Subject: vv.Condition.Range().Ptr(),
})
}
}
if attr, exists := content.Attributes["error_message"]; exists {
moreDiags := gohcl.DecodeExpression(attr.Expr, nil, &vv.ErrorMessage)
diags = append(diags, moreDiags...)
if !moreDiags.HasErrors() {
const errSummary = "Invalid validation error message"
switch {
case vv.ErrorMessage == "":
diags = diags.Append(&hcl.Diagnostic{
Severity: hcl.DiagError,
Summary: errSummary,
Detail: "An empty string is not a valid nor useful error message.",
Subject: attr.Expr.Range().Ptr(),
})
case !looksLikeSentences(vv.ErrorMessage):
// Because we're going to include this string verbatim as part
// of a bigger error message written in our usual style in
// English, we'll require the given error message to conform
// to that. We might relax this in future if e.g. we start
// presenting these error messages in a different way, or if
// Terraform starts supporting producing error messages in
// other human languages, etc.
// For pragmatism we also allow sentences ending with
// exclamation points, but we don't mention it explicitly here
// because that's not really consistent with the Terraform UI
// writing style.
diags = diags.Append(&hcl.Diagnostic{
Severity: hcl.DiagError,
Summary: errSummary,
Detail: "The validation error message must be at least one full sentence starting with an uppercase letter and ending with a period or question mark.\n\nYour given message will be included as part of a larger Terraform error message, written as English prose. For broadly-shared modules we suggest using a similar writing style so that the overall result will be consistent.",
Subject: attr.Expr.Range().Ptr(),
})
}
}
}
return vv, diags
}
// looksLikeSentence is a simple heuristic that encourages writing error
// messages that will be presentable when included as part of a larger
// Terraform error diagnostic whose other text is written in the Terraform
// UI writing style.
//
// This is intentionally not a very strong validation since we're assuming
// that module authors want to write good messages and might just need a nudge
// about Terraform's specific style, rather than that they are going to try
// to work around these rules to write a lower-quality message.
func looksLikeSentences(s string) bool {
if len(s) < 1 {
return false
}
runes := []rune(s) // HCL guarantees that all strings are valid UTF-8
first := runes[0]
last := runes[len(runes)-1]
// If the first rune is a letter then it must be an uppercase letter.
// (This will only see the first rune in a multi-rune combining sequence,
// but the first rune is generally the letter if any are, and if not then
// we'll just ignore it because we're primarily expecting English messages
// right now anyway, for consistency with all of Terraform's other output.)
if unicode.IsLetter(first) && !unicode.IsUpper(first) {
return false
}
// The string must be at least one full sentence, which implies having
// sentence-ending punctuation.
// (This assumes that if a sentence ends with quotes then the period
// will be outside the quotes, which is consistent with Terraform's UI
// writing style.)
return last == '.' || last == '?' || last == '!'
}
// Output represents an "output" block in a module or file.
type Output struct {
Name string
@ -592,19 +481,6 @@ var variableBlockSchema = &hcl.BodySchema{
},
}
var variableValidationBlockSchema = &hcl.BodySchema{
Attributes: []hcl.AttributeSchema{
{
Name: "condition",
Required: true,
},
{
Name: "error_message",
Required: true,
},
},
}
var outputBlockSchema = &hcl.BodySchema{
Attributes: []hcl.AttributeSchema{
{

2
internal/terraform/node_root_variable_test.go
View File

@ -79,7 +79,7 @@ func TestNodeRootVariableExecute(t *testing.T) {
Name: "foo",
Type: cty.Number,
ConstraintType: cty.Number,
Validations: []*configs.VariableValidation{
Validations: []*configs.CheckRule{
{
Condition: fakeHCLExpressionFunc(func(ctx *hcl.EvalContext) (cty.Value, hcl.Diagnostics) {
// This returns true only if the given variable value