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package hclsyntax
import (
"bytes"
"fmt"
"path/filepath"
"runtime"
"strings"
"github.com/hashicorp/hcl2/hcl"
)
// This is set to true at init() time in tests, to enable more useful output
// if a stack discipline error is detected. It should not be enabled in
// normal mode since there is a performance penalty from accessing the
// runtime stack to produce the traces, but could be temporarily set to
// true for debugging if desired.
var tracePeekerNewlinesStack = false
type peeker struct {
Tokens Tokens
NextIndex int
IncludeComments bool
IncludeNewlinesStack []bool
// used only when tracePeekerNewlinesStack is set
newlineStackChanges []peekerNewlineStackChange
}
// for use in debugging the stack usage only
type peekerNewlineStackChange struct {
Pushing bool // if false, then popping
Frame runtime.Frame
Include bool
}
func newPeeker(tokens Tokens, includeComments bool) *peeker {
return &peeker{
Tokens: tokens,
IncludeComments: includeComments,
IncludeNewlinesStack: []bool{true},
}
}
func (p *peeker) Peek() Token {
ret, _ := p.nextToken()
return ret
}
func (p *peeker) Read() Token {
ret, nextIdx := p.nextToken()
p.NextIndex = nextIdx
return ret
}
func (p *peeker) NextRange() hcl.Range {
return p.Peek().Range
}
func (p *peeker) PrevRange() hcl.Range {
if p.NextIndex == 0 {
return p.NextRange()
}
return p.Tokens[p.NextIndex-1].Range
}
func (p *peeker) nextToken() (Token, int) {
for i := p.NextIndex; i < len(p.Tokens); i++ {
tok := p.Tokens[i]
switch tok.Type {
case TokenComment:
if !p.IncludeComments {
// Single-line comment tokens, starting with # or //, absorb
// the trailing newline that terminates them as part of their
// bytes. When we're filtering out comments, we must as a
// special case transform these to newline tokens in order
// to properly parse newline-terminated block items.
if p.includingNewlines() {
if len(tok.Bytes) > 0 && tok.Bytes[len(tok.Bytes)-1] == '\n' {
fakeNewline := Token{
Type: TokenNewline,
Bytes: tok.Bytes[len(tok.Bytes)-1 : len(tok.Bytes)],
// We use the whole token range as the newline
// range, even though that's a little... weird,
// because otherwise we'd need to go count
// characters again in order to figure out the
// column of the newline, and that complexity
// isn't justified when ranges of newlines are
// so rarely printed anyway.
Range: tok.Range,
}
return fakeNewline, i + 1
}
}
continue
}
case TokenNewline:
if !p.includingNewlines() {
continue
}
}
return tok, i + 1
}
// if we fall out here then we'll return the EOF token, and leave
// our index pointed off the end of the array so we'll keep
// returning EOF in future too.
return p.Tokens[len(p.Tokens)-1], len(p.Tokens)
}
func (p *peeker) includingNewlines() bool {
return p.IncludeNewlinesStack[len(p.IncludeNewlinesStack)-1]
}
func (p *peeker) PushIncludeNewlines(include bool) {
if tracePeekerNewlinesStack {
// Record who called us so that we can more easily track down any
// mismanagement of the stack in the parser.
callers := []uintptr{0}
runtime.Callers(2, callers)
frames := runtime.CallersFrames(callers)
frame, _ := frames.Next()
p.newlineStackChanges = append(p.newlineStackChanges, peekerNewlineStackChange{
true, frame, include,
})
}
p.IncludeNewlinesStack = append(p.IncludeNewlinesStack, include)
}
func (p *peeker) PopIncludeNewlines() bool {
stack := p.IncludeNewlinesStack
remain, ret := stack[:len(stack)-1], stack[len(stack)-1]
p.IncludeNewlinesStack = remain
if tracePeekerNewlinesStack {
// Record who called us so that we can more easily track down any
// mismanagement of the stack in the parser.
callers := []uintptr{0}
runtime.Callers(2, callers)
frames := runtime.CallersFrames(callers)
frame, _ := frames.Next()
p.newlineStackChanges = append(p.newlineStackChanges, peekerNewlineStackChange{
false, frame, ret,
})
}
return ret
}
// AssertEmptyNewlinesStack checks if the IncludeNewlinesStack is empty, doing
// panicking if it is not. This can be used to catch stack mismanagement that
// might otherwise just cause confusing downstream errors.
//
// This function is a no-op if the stack is empty when called.
//
// If newlines stack tracing is enabled by setting the global variable
// tracePeekerNewlinesStack at init time, a full log of all of the push/pop
// calls will be produced to help identify which caller in the parser is
// misbehaving.
func (p *peeker) AssertEmptyIncludeNewlinesStack() {
if len(p.IncludeNewlinesStack) != 1 {
// Should never happen; indicates mismanagement of the stack inside
// the parser.
if p.newlineStackChanges != nil { // only if traceNewlinesStack is enabled above
panic(fmt.Errorf(
"non-empty IncludeNewlinesStack after parse with %d calls unaccounted for:\n%s",
len(p.IncludeNewlinesStack)-1,
formatPeekerNewlineStackChanges(p.newlineStackChanges),
))
} else {
panic(fmt.Errorf("non-empty IncludeNewlinesStack after parse: %#v", p.IncludeNewlinesStack))
}
}
}
func formatPeekerNewlineStackChanges(changes []peekerNewlineStackChange) string {
indent := 0
var buf bytes.Buffer
for _, change := range changes {
funcName := change.Frame.Function
if idx := strings.LastIndexByte(funcName, '.'); idx != -1 {
funcName = funcName[idx+1:]
}
filename := change.Frame.File
if idx := strings.LastIndexByte(filename, filepath.Separator); idx != -1 {
filename = filename[idx+1:]
}
switch change.Pushing {
case true:
buf.WriteString(strings.Repeat(" ", indent))
fmt.Fprintf(&buf, "PUSH %#v (%s at %s:%d)\n", change.Include, funcName, filename, change.Frame.Line)
indent++
case false:
indent--
buf.WriteString(strings.Repeat(" ", indent))
fmt.Fprintf(&buf, "POP %#v (%s at %s:%d)\n", change.Include, funcName, filename, change.Frame.Line)
}
}
return buf.String()
}
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