tfdiags

Documentation

Overview

Package tfdiags is a utility package for representing errors and warnings in a manner that allows us to produce good messages for the user.

"diag" is short for "diagnostics", and is meant as a general word for feedback to a user about potential or actual problems.

A design goal for this package is for it to be able to provide rich messaging where possible but to also be pragmatic about dealing with generic errors produced by system components that _can't_ provide such rich messaging. As a consequence, the main types in this package -- Diagnostics and Diagnostic -- are designed so that they can be "smuggled" over an error channel and then be unpacked at the other end, so that error diagnostics (at least) can transit through APIs that are not aware of this package.

Index

• func FormatCtyPath(path cty.Path) string
• func FormatError(err error) string
• func FormatErrorPrefixed(err error, prefix string) string
• func GetAttribute(d Diagnostic) cty.Path
• type Description
• type Diagnostic
  • func AttributeValue(severity Severity, summary, detail string, attrPath cty.Path) Diagnostic
  • func SimpleWarning(msg string) Diagnostic
  • func Sourceless(severity Severity, summary, detail string) Diagnostic
  • func WholeContainingBody(severity Severity, summary, detail string) Diagnostic
• type Diagnostics
  • func (diags Diagnostics) Append(new ...interface{}) Diagnostics
  • func (diags Diagnostics) ConsolidateWarnings(threshold int) Diagnostics
  • func (diags Diagnostics) Err() error
  • func (diags Diagnostics) ErrWithWarnings() error
  • func (diags Diagnostics) ForRPC() Diagnostics
  • func (diags Diagnostics) HasErrors() bool
  • func (d Diagnostics) InConfigBody(body hcl.Body) Diagnostics
  • func (diags Diagnostics) NonFatalErr() error
  • func (diags Diagnostics) Sort()
• type FromExpr
• type NonFatalError
  • func (woe NonFatalError) Error() string
• type Severity
  • func (i Severity) String() string
• type Source
  • func WarningGroupSourceRanges(diag Diagnostic) []Source
• type SourcePos
• type SourceRange
  • func SourceRangeFromHCL(hclRange hcl.Range) SourceRange
  • func (r SourceRange) StartString() string
  • func (r SourceRange) ToHCL() hcl.Range

Functions

func FormatCtyPath

func FormatCtyPath(path cty.Path) string

FormatCtyPath is a helper function to produce a user-friendly string representation of a cty.Path. The result uses a syntax similar to the HCL expression language in the hope of it being familiar to users.

func FormatError

func FormatError(err error) string

FormatError is a helper function to produce a user-friendly string representation of certain special error types that we might want to include in diagnostic messages.

This currently has special behavior only for cty.PathError, where a non-empty path is rendered in a HCL-like syntax as context.

func FormatErrorPrefixed

func FormatErrorPrefixed(err error, prefix string) string

FormatErrorPrefixed is like FormatError except that it presents any path information after the given prefix string, which is assumed to contain an HCL syntax representation of the value that errors are relative to.

func GetAttribute

func GetAttribute(d Diagnostic) cty.Path

GetAttribute extracts an attribute cty.Path from a diagnostic if it contains one. Normally this is not accessed directly, and instead the config body is added to the Diagnostic to create a more complete message for the user. In some cases however, we may want to know just the name of the attribute that generated the Diagnostic message. This returns a nil cty.Path if it does not exist in the Diagnostic.

Types

type Description

type Description struct {
	Summary string
	Detail  string
}

type Diagnostic

type Diagnostic interface {
	Severity() Severity
	Description() Description
	Source() Source

	// FromExpr returns the expression-related context for the diagnostic, if
	// available. Returns nil if the diagnostic is not related to an
	// expression evaluation.
	FromExpr() *FromExpr
}

func AttributeValue

func AttributeValue(severity Severity, summary, detail string, attrPath cty.Path) Diagnostic

AttributeValue returns a diagnostic about an attribute value in an implied current configuration context. This should be returned only from functions whose interface specifies a clear configuration context that this will be resolved in.

The given path is relative to the implied configuration context. To describe a top-level attribute, it should be a single-element cty.Path with a cty.GetAttrStep. It's assumed that the path is returning into a structure that would be produced by our conventions in the configschema package; it may return unexpected results for structures that can't be represented by configschema.

Since mapping attribute paths back onto configuration is an imprecise operation (e.g. dynamic block generation may cause the same block to be evaluated multiple times) the diagnostic detail should include the attribute name and other context required to help the user understand what is being referenced in case the identified source range is not unique.

The returned attribute will not have source location information until context is applied to the containing diagnostics using diags.InConfigBody. After context is applied, the source location is the value assigned to the named attribute, or the containing body's "missing item range" if no value is present.

func SimpleWarning

func SimpleWarning(msg string) Diagnostic

SimpleWarning constructs a simple (summary-only) warning diagnostic.

func Sourceless

func Sourceless(severity Severity, summary, detail string) Diagnostic

Sourceless creates and returns a diagnostic with no source location information. This is generally used for operational-type errors that are caused by or relate to the environment where Terraform is running rather than to the provided configuration.

func WholeContainingBody

func WholeContainingBody(severity Severity, summary, detail string) Diagnostic

WholeContainingBody returns a diagnostic about the body that is an implied current configuration context. This should be returned only from functions whose interface specifies a clear configuration context that this will be resolved in.

The returned attribute will not have source location information until context is applied to the containing diagnostics using diags.InConfigBody. After context is applied, the source location is currently the missing item range of the body. In future, this may change to some other suitable part of the containing body.

type Diagnostics

type Diagnostics []Diagnostic

Diagnostics is a list of diagnostics. Diagnostics is intended to be used where a Go "error" might normally be used, allowing richer information to be conveyed (more context, support for warnings).

A nil Diagnostics is a valid, empty diagnostics list, thus allowing heap allocation to be avoided in the common case where there are no diagnostics to report at all.

func (Diagnostics) Append

func (diags Diagnostics) Append(new ...interface{}) Diagnostics

Append is the main interface for constructing Diagnostics lists, taking an existing list (which may be nil) and appending the new objects to it after normalizing them to be implementations of Diagnostic.

The usual pattern for a function that natively "speaks" diagnostics is:

// Create a nil Diagnostics at the start of the function
var diags diag.Diagnostics

// At later points, build on it if errors / warnings occur:
foo, err := DoSomethingRisky()
if err != nil {
    diags = diags.Append(err)
}

// Eventually return the result and diagnostics in place of error
return result, diags

Append accepts a variety of different diagnostic-like types, including native Go errors and HCL diagnostics. It also knows how to unwrap a multierror.Error into separate error diagnostics. It can be passed another Diagnostics to concatenate the two lists. If given something it cannot handle, this function will panic.

func (Diagnostics) ConsolidateWarnings

func (diags Diagnostics) ConsolidateWarnings(threshold int) Diagnostics

ConsolidateWarnings checks if there is an unreasonable amount of warnings with the same summary in the receiver and, if so, returns a new diagnostics with some of those warnings consolidated into a single warning in order to reduce the verbosity of the output.

This mechanism is here primarily for diagnostics printed out at the CLI. In other contexts it is likely better to just return the warnings directly, particularly if they are going to be interpreted by software rather than by a human reader.

The returned slice always has a separate backing array from the reciever, but some diagnostic values themselves might be shared.

The definition of "unreasonable" is given as the threshold argument. At most that many warnings with the same summary will be shown.

func (Diagnostics) Err

func (diags Diagnostics) Err() error

Err flattens a diagnostics list into a single Go error, or to nil if the diagnostics list does not include any error-level diagnostics.

This can be used to smuggle diagnostics through an API that deals in native errors, but unfortunately it will lose naked warnings (warnings that aren't accompanied by at least one error) since such APIs have no mechanism through which to report these.

return result, diags.Error()

func (Diagnostics) ErrWithWarnings

func (diags Diagnostics) ErrWithWarnings() error

ErrWithWarnings is similar to Err except that it will also return a non-nil error if the receiver contains only warnings.

In the warnings-only situation, the result is guaranteed to be of dynamic type NonFatalError, allowing diagnostics-aware callers to type-assert and unwrap it, treating it as non-fatal.

This should be used only in contexts where the caller is able to recognize and handle NonFatalError. For normal callers that expect a lack of errors to be signaled by nil, use just Diagnostics.Err.

func (Diagnostics) ForRPC

func (diags Diagnostics) ForRPC() Diagnostics

ForRPC returns a version of the receiver that has been simplified so that it is friendly to RPC protocols.

Currently this means that it can be serialized with encoding/gob and subsequently re-inflated. It may later grow to include other serialization formats.

Note that this loses information about the original objects used to construct the diagnostics, so e.g. the errwrap API will not work as expected on an error-wrapped Diagnostics that came from ForRPC.

func (Diagnostics) HasErrors

func (diags Diagnostics) HasErrors() bool

HasErrors returns true if any of the diagnostics in the list have a severity of Error.

func (Diagnostics) InConfigBody

func (d Diagnostics) InConfigBody(body hcl.Body) Diagnostics

InConfigBody returns a copy of the receiver with any config-contextual diagnostics elaborated in the context of the given body.

func (Diagnostics) NonFatalErr

func (diags Diagnostics) NonFatalErr() error

NonFatalErr is similar to Err except that it always returns either nil (if there are no diagnostics at all) or NonFatalError.

This allows diagnostics to be returned over an error return channel while being explicit that the diagnostics should not halt processing.

This should be used only in contexts where the caller is able to recognize and handle NonFatalError. For normal callers that expect a lack of errors to be signaled by nil, use just Diagnostics.Err.

func (Diagnostics) Sort

func (diags Diagnostics) Sort()

Sort applies an ordering to the diagnostics in the receiver in-place.

The ordering is: warnings before errors, sourceless before sourced, short source paths before long source paths, and then ordering by position within each file.

Diagnostics that do not differ by any of these sortable characteristics will remain in the same relative order after this method returns.

type FromExpr

type FromExpr struct {
	Expression  hcl.Expression
	EvalContext *hcl.EvalContext
}

type NonFatalError

type NonFatalError struct {
	Diagnostics
}

NonFatalError is a special error type, returned by Diagnostics.ErrWithWarnings and Diagnostics.NonFatalErr, that indicates that the wrapped diagnostics should be treated as non-fatal. Callers can conditionally type-assert an error to this type in order to detect the non-fatal scenario and handle it in a different way.

func (NonFatalError) Error

func (woe NonFatalError) Error() string

type Severity

type Severity rune

const (
	Error   Severity = 'E'
	Warning Severity = 'W'
)

func (Severity) String

func (i Severity) String() string

type Source

type Source struct {
	Subject *SourceRange
	Context *SourceRange
}

func WarningGroupSourceRanges

func WarningGroupSourceRanges(diag Diagnostic) []Source

WarningGroupSourceRanges can be used in conjunction with Diagnostics.ConsolidateWarnings to recover the full set of original source locations from a consolidated warning.

For convenience, this function accepts any diagnostic and will just return the single Source value from any diagnostic that isn't a warning group.

type SourcePos

type SourcePos struct {
	Line, Column, Byte int
}

type SourceRange

type SourceRange struct {
	Filename   string
	Start, End SourcePos
}

func SourceRangeFromHCL

func SourceRangeFromHCL(hclRange hcl.Range) SourceRange

SourceRangeFromHCL constructs a SourceRange from the corresponding range type within the HCL package.

func (SourceRange) StartString

func (r SourceRange) StartString() string

StartString returns a string representation of the start of the range, including the filename and the line and column numbers.

func (SourceRange) ToHCL

func (r SourceRange) ToHCL() hcl.Range

ToHCL constructs a HCL Range from the receiving SourceRange. This is the opposite of SourceRangeFromHCL.