mirror of https://github.com/hashicorp/terraform
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.pull/30401/head
Martin Atkins
6 years ago
committed by
Alisdair McDiarmid
parent
0900c7e0bb
commit
4f41a0a1fe
@ -0,0 +1,152 @@
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package configs
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import (
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"fmt"
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"unicode"
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"github.com/hashicorp/hcl/v2"
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"github.com/hashicorp/hcl/v2/gohcl"
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)
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// CheckRule represents a configuration-defined validation rule, precondition,
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// or postcondition. Blocks of this sort can appear in a few different places
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// in configuration, including "validation" blocks for variables,
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// and "precondition" and "postcondition" blocks for resources.
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type CheckRule struct {
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// Condition is an expression that must evaluate to true if the condition
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// holds or false if it does not. If the expression produces an error then
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// that's considered to be a bug in the module defining the check.
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//
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// The available variables in a condition expression vary depending on what
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// a check is attached to. For example, validation rules attached to
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// input variables can only refer to the variable that is being validated.
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Condition hcl.Expression
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// ErrorMessage is one or more full sentences, which would need to be in
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// English for consistency with the rest of the error message output but
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// can in practice be in any language as long as it ends with a period.
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// The message should describe what is required for the condition to return
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// true in a way that would make sense to a caller of the module.
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ErrorMessage string
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DeclRange hcl.Range
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}
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// decodeCheckRuleBlock decodes the contents of the given block as a check rule.
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//
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// Unlike most of our "decode..." functions, this one can be applied to blocks
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// of various types as long as their body structures are "check-shaped". The
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// function takes the containing block only because some error messages will
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// refer to its location, and the returned object's DeclRange will be the
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// block's header.
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func decodeCheckRuleBlock(block *hcl.Block, override bool) (*CheckRule, hcl.Diagnostics) {
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var diags hcl.Diagnostics
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cr := &CheckRule{
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DeclRange: block.DefRange,
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}
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if override {
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// For now we'll just forbid overriding check blocks, to simplify
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// the initial design. If we can find a clear use-case for overriding
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// checks in override files and there's a way to define it that
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// isn't confusing then we could relax this.
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diags = diags.Append(&hcl.Diagnostic{
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Severity: hcl.DiagError,
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Summary: fmt.Sprintf("Can't override %s blocks", block.Type),
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Detail: fmt.Sprintf("Override files cannot override %q blocks.", block.Type),
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Subject: cr.DeclRange.Ptr(),
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})
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return cr, diags
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}
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content, moreDiags := block.Body.Content(checkRuleBlockSchema)
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diags = append(diags, moreDiags...)
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if attr, exists := content.Attributes["condition"]; exists {
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cr.Condition = attr.Expr
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}
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if attr, exists := content.Attributes["error_message"]; exists {
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moreDiags := gohcl.DecodeExpression(attr.Expr, nil, &cr.ErrorMessage)
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diags = append(diags, moreDiags...)
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if !moreDiags.HasErrors() {
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const errSummary = "Invalid validation error message"
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switch {
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case cr.ErrorMessage == "":
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diags = diags.Append(&hcl.Diagnostic{
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Severity: hcl.DiagError,
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Summary: errSummary,
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Detail: "An empty string is not a valid nor useful error message.",
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Subject: attr.Expr.Range().Ptr(),
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})
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case !looksLikeSentences(cr.ErrorMessage):
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// Because we're going to include this string verbatim as part
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// of a bigger error message written in our usual style in
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// English, we'll require the given error message to conform
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// to that. We might relax this in future if e.g. we start
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// presenting these error messages in a different way, or if
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// Terraform starts supporting producing error messages in
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// other human languages, etc.
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// For pragmatism we also allow sentences ending with
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// exclamation points, but we don't mention it explicitly here
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// because that's not really consistent with the Terraform UI
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// writing style.
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diags = diags.Append(&hcl.Diagnostic{
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Severity: hcl.DiagError,
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Summary: errSummary,
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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.",
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Subject: attr.Expr.Range().Ptr(),
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})
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}
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}
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}
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return cr, diags
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}
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// looksLikeSentence is a simple heuristic that encourages writing error
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// messages that will be presentable when included as part of a larger
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// Terraform error diagnostic whose other text is written in the Terraform
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// UI writing style.
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//
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// This is intentionally not a very strong validation since we're assuming
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// that module authors want to write good messages and might just need a nudge
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// about Terraform's specific style, rather than that they are going to try
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// to work around these rules to write a lower-quality message.
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func looksLikeSentences(s string) bool {
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if len(s) < 1 {
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return false
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}
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runes := []rune(s) // HCL guarantees that all strings are valid UTF-8
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first := runes[0]
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last := runes[len(runes)-1]
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// If the first rune is a letter then it must be an uppercase letter.
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// (This will only see the first rune in a multi-rune combining sequence,
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// but the first rune is generally the letter if any are, and if not then
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// we'll just ignore it because we're primarily expecting English messages
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// right now anyway, for consistency with all of Terraform's other output.)
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if unicode.IsLetter(first) && !unicode.IsUpper(first) {
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return false
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}
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// The string must be at least one full sentence, which implies having
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// sentence-ending punctuation.
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// (This assumes that if a sentence ends with quotes then the period
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// will be outside the quotes, which is consistent with Terraform's UI
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// writing style.)
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return last == '.' || last == '?' || last == '!'
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}
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var checkRuleBlockSchema = &hcl.BodySchema{
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Attributes: []hcl.AttributeSchema{
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{
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Name: "condition",
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Required: true,
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},
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{
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Name: "error_message",
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Required: true,
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},
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},
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}
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