package hclsyntax
import (
"fmt"
"strings"
"unicode"
"github.com/hashicorp/hcl2/hcl"
"github.com/zclconf/go-cty/cty"
)
func (p *parser) ParseTemplate() (Expression, hcl.Diagnostics) {
return p.parseTemplate(TokenEOF)
}
func (p *parser) parseTemplate(end TokenType) (Expression, hcl.Diagnostics) {
exprs, passthru, rng, diags := p.parseTemplateInner(end)
if passthru {
if len(exprs) != 1 {
panic("passthru set with len(exprs) != 1")
}
return &TemplateWrapExpr{
Wrapped: exprs[0],
SrcRange: rng,
}, diags
}
return &TemplateExpr{
Parts: exprs,
SrcRange: rng,
}, diags
}
func (p *parser) parseTemplateInner(end TokenType) ([]Expression, bool, hcl.Range, hcl.Diagnostics) {
parts, diags := p.parseTemplateParts(end)
tp := templateParser{
Tokens: parts.Tokens,
SrcRange: parts.SrcRange,
}
exprs, exprsDiags := tp.parseRoot()
diags = append(diags, exprsDiags...)
passthru := false
if len(parts.Tokens) == 2 { // one real token and one synthetic "end" token
if _, isInterp := parts.Tokens[0].(*templateInterpToken); isInterp {
passthru = true
}
}
return exprs, passthru, parts.SrcRange, diags
}
type templateParser struct {
Tokens []templateToken
SrcRange hcl.Range
pos int
}
func (p *templateParser) parseRoot() ([]Expression, hcl.Diagnostics) {
var exprs []Expression
var diags hcl.Diagnostics
for {
next := p.Peek()
if _, isEnd := next.(*templateEndToken); isEnd {
break
}
expr, exprDiags := p.parseExpr()
diags = append(diags, exprDiags...)
exprs = append(exprs, expr)
}
return exprs, diags
}
func (p *templateParser) parseExpr() (Expression, hcl.Diagnostics) {
next := p.Peek()
switch tok := next.(type) {
case *templateLiteralToken:
p.Read() // eat literal
return &LiteralValueExpr{
Val: cty.StringVal(tok.Val),
SrcRange: tok.SrcRange,
}, nil
case *templateInterpToken:
p.Read() // eat interp
return tok.Expr, nil
case *templateIfToken:
return p.parseIf()
case *templateForToken:
return p.parseFor()
case *templateEndToken:
p.Read() // eat erroneous token
return errPlaceholderExpr(tok.SrcRange), hcl.Diagnostics{
{
// This is a particularly unhelpful diagnostic, so callers
// should attempt to pre-empt it and produce a more helpful
// diagnostic that is context-aware.
Severity: hcl.DiagError,
Summary: "Unexpected end of template",
Detail: "The control directives within this template are unbalanced.",
Subject: &tok.SrcRange,
},
}
case *templateEndCtrlToken:
p.Read() // eat erroneous token
return errPlaceholderExpr(tok.SrcRange), hcl.Diagnostics{
{
Severity: hcl.DiagError,
Summary: fmt.Sprintf("Unexpected %s directive", tok.Name()),
Detail: "The control directives within this template are unbalanced.",
Subject: &tok.SrcRange,
},
}
default:
// should never happen, because above should be exhaustive
panic(fmt.Sprintf("unhandled template token type %T", next))
}
}
func (p *templateParser) parseIf() (Expression, hcl.Diagnostics) {
open := p.Read()
openIf, isIf := open.(*templateIfToken)
if !isIf {
// should never happen if caller is behaving
panic("parseIf called with peeker not pointing at if token")
}
var ifExprs, elseExprs []Expression
var diags hcl.Diagnostics
var endifRange hcl.Range
currentExprs := &ifExprs
Token:
for {
next := p.Peek()
if end, isEnd := next.(*templateEndToken); isEnd {
diags = append(diags, &hcl.Diagnostic{
Severity: hcl.DiagError,
Summary: "Unexpected end of template",
Detail: fmt.Sprintf(
"The if directive at %s is missing its corresponding endif directive.",
openIf.SrcRange,
),
Subject: &end.SrcRange,
})
return errPlaceholderExpr(end.SrcRange), diags
}
if end, isCtrlEnd := next.(*templateEndCtrlToken); isCtrlEnd {
p.Read() // eat end directive
switch end.Type {
case templateElse:
if currentExprs == &ifExprs {
currentExprs = &elseExprs
continue Token
}
diags = append(diags, &hcl.Diagnostic{
Severity: hcl.DiagError,
Summary: "Unexpected else directive",
Detail: fmt.Sprintf(
"Already in the else clause for the if started at %s.",
openIf.SrcRange,
),
Subject: &end.SrcRange,
})
case templateEndIf:
endifRange = end.SrcRange
break Token
default:
diags = append(diags, &hcl.Diagnostic{
Severity: hcl.DiagError,
Summary: fmt.Sprintf("Unexpected %s directive", end.Name()),
Detail: fmt.Sprintf(
"Expecting an endif directive for the if started at %s.",
openIf.SrcRange,
),
Subject: &end.SrcRange,
})
}
return errPlaceholderExpr(end.SrcRange), diags
}
expr, exprDiags := p.parseExpr()
diags = append(diags, exprDiags...)
*currentExprs = append(*currentExprs, expr)
}
if len(ifExprs) == 0 {
ifExprs = append(ifExprs, &LiteralValueExpr{
Val: cty.StringVal(""),
SrcRange: hcl.Range{
Filename: openIf.SrcRange.Filename,
Start: openIf.SrcRange.End,
End: openIf.SrcRange.End,
},
})
}
if len(elseExprs) == 0 {
elseExprs = append(elseExprs, &LiteralValueExpr{
Val: cty.StringVal(""),
SrcRange: hcl.Range{
Filename: endifRange.Filename,
Start: endifRange.Start,
End: endifRange.Start,
},
})
}
trueExpr := &TemplateExpr{
Parts: ifExprs,
SrcRange: hcl.RangeBetween(ifExprs[0].Range(), ifExprs[len(ifExprs)-1].Range()),
}
falseExpr := &TemplateExpr{
Parts: elseExprs,
SrcRange: hcl.RangeBetween(elseExprs[0].Range(), elseExprs[len(elseExprs)-1].Range()),
}
return &ConditionalExpr{
Condition: openIf.CondExpr,
TrueResult: trueExpr,
FalseResult: falseExpr,
SrcRange: hcl.RangeBetween(openIf.SrcRange, endifRange),
}, diags
}
func (p *templateParser) parseFor() (Expression, hcl.Diagnostics) {
open := p.Read()
openFor, isFor := open.(*templateForToken)
if !isFor {
// should never happen if caller is behaving
panic("parseFor called with peeker not pointing at for token")
}
var contentExprs []Expression
var diags hcl.Diagnostics
var endforRange hcl.Range
Token:
for {
next := p.Peek()
if end, isEnd := next.(*templateEndToken); isEnd {
diags = append(diags, &hcl.Diagnostic{
Severity: hcl.DiagError,
Summary: "Unexpected end of template",
Detail: fmt.Sprintf(
"The for directive at %s is missing its corresponding endfor directive.",
openFor.SrcRange,
),
Subject: &end.SrcRange,
})
return errPlaceholderExpr(end.SrcRange), diags
}
if end, isCtrlEnd := next.(*templateEndCtrlToken); isCtrlEnd {
p.Read() // eat end directive
switch end.Type {
case templateElse:
diags = append(diags, &hcl.Diagnostic{
Severity: hcl.DiagError,
Summary: "Unexpected else directive",
Detail: "An else clause is not expected for a for directive.",
Subject: &end.SrcRange,
})
case templateEndFor:
endforRange = end.SrcRange
break Token
default:
diags = append(diags, &hcl.Diagnostic{
Severity: hcl.DiagError,
Summary: fmt.Sprintf("Unexpected %s directive", end.Name()),
Detail: fmt.Sprintf(
"Expecting an endfor directive corresponding to the for directive at %s.",
openFor.SrcRange,
),
Subject: &end.SrcRange,
})
}
return errPlaceholderExpr(end.SrcRange), diags
}
expr, exprDiags := p.parseExpr()
diags = append(diags, exprDiags...)
contentExprs = append(contentExprs, expr)
}
if len(contentExprs) == 0 {
contentExprs = append(contentExprs, &LiteralValueExpr{
Val: cty.StringVal(""),
SrcRange: hcl.Range{
Filename: openFor.SrcRange.Filename,
Start: openFor.SrcRange.End,
End: openFor.SrcRange.End,
},
})
}
contentExpr := &TemplateExpr{
Parts: contentExprs,
SrcRange: hcl.RangeBetween(contentExprs[0].Range(), contentExprs[len(contentExprs)-1].Range()),
}
forExpr := &ForExpr{
KeyVar: openFor.KeyVar,
ValVar: openFor.ValVar,
CollExpr: openFor.CollExpr,
ValExpr: contentExpr,
SrcRange: hcl.RangeBetween(openFor.SrcRange, endforRange),
OpenRange: openFor.SrcRange,
CloseRange: endforRange,
}
return &TemplateJoinExpr{
Tuple: forExpr,
}, diags
}
func (p *templateParser) Peek() templateToken {
return p.Tokens[p.pos]
}
func (p *templateParser) Read() templateToken {
ret := p.Peek()
if _, end := ret.(*templateEndToken); !end {
p.pos++
}
return ret
}
// parseTemplateParts produces a flat sequence of "template tokens", which are
// either literal values (with any "trimming" already applied), interpolation
// sequences, or control flow markers.
//
// A further pass is required on the result to turn it into an AST.
func (p *parser) parseTemplateParts(end TokenType) (*templateParts, hcl.Diagnostics) {
var parts []templateToken
var diags hcl.Diagnostics
startRange := p.NextRange()
ltrimNext := false
nextCanTrimPrev := false
var endRange hcl.Range
Token:
for {
next := p.Read()
if next.Type == end {
// all done!
endRange = next.Range
break
}
ltrim := ltrimNext
ltrimNext = false
canTrimPrev := nextCanTrimPrev
nextCanTrimPrev = false
switch next.Type {
case TokenStringLit, TokenQuotedLit:
str, strDiags := p.decodeStringLit(next)
diags = append(diags, strDiags...)
if ltrim {
str = strings.TrimLeftFunc(str, unicode.IsSpace)
}
parts = append(parts, &templateLiteralToken{
Val: str,
SrcRange: next.Range,
})
nextCanTrimPrev = true
case TokenTemplateInterp:
// if the opener is ${~ then we want to eat any trailing whitespace
// in the preceding literal token, assuming it is indeed a literal
// token.
if canTrimPrev && len(next.Bytes) == 3 && next.Bytes[2] == '~' && len(parts) > 0 {
prevExpr := parts[len(parts)-1]
if lexpr, ok := prevExpr.(*templateLiteralToken); ok {
lexpr.Val = strings.TrimRightFunc(lexpr.Val, unicode.IsSpace)
}
}
p.PushIncludeNewlines(false)
expr, exprDiags := p.ParseExpression()
diags = append(diags, exprDiags...)
close := p.Peek()
if close.Type != TokenTemplateSeqEnd {
if !p.recovery {
diags = append(diags, &hcl.Diagnostic{
Severity: hcl.DiagError,
Summary: "Extra characters after interpolation expression",
Detail: "Expected a closing brace to end the interpolation expression, but found extra characters.",
Subject: &close.Range,
Context: hcl.RangeBetween(startRange, close.Range).Ptr(),
})
}
p.recover(TokenTemplateSeqEnd)
} else {
p.Read() // eat closing brace
// If the closer is ~} then we want to eat any leading
// whitespace on the next token, if it turns out to be a
// literal token.
if len(close.Bytes) == 2 && close.Bytes[0] == '~' {
ltrimNext = true
}
}
p.PopIncludeNewlines()
parts = append(parts, &templateInterpToken{
Expr: expr,
SrcRange: hcl.RangeBetween(next.Range, close.Range),
})
case TokenTemplateControl:
// if the opener is %{~ then we want to eat any trailing whitespace
// in the preceding literal token, assuming it is indeed a literal
// token.
if canTrimPrev && len(next.Bytes) == 3 && next.Bytes[2] == '~' && len(parts) > 0 {
prevExpr := parts[len(parts)-1]
if lexpr, ok := prevExpr.(*templateLiteralToken); ok {
lexpr.Val = strings.TrimRightFunc(lexpr.Val, unicode.IsSpace)
}
}
p.PushIncludeNewlines(false)
kw := p.Peek()
if kw.Type != TokenIdent {
if !p.recovery {
diags = append(diags, &hcl.Diagnostic{
Severity: hcl.DiagError,
Summary: "Invalid template directive",
Detail: "A template directive keyword (\"if\", \"for\", etc) is expected at the beginning of a %{ sequence.",
Subject: &kw.Range,
Context: hcl.RangeBetween(next.Range, kw.Range).Ptr(),
})
}
p.recover(TokenTemplateSeqEnd)
p.PopIncludeNewlines()
continue Token
}
p.Read() // eat keyword token
switch {
case ifKeyword.TokenMatches(kw):
condExpr, exprDiags := p.ParseExpression()
diags = append(diags, exprDiags...)
parts = append(parts, &templateIfToken{
CondExpr: condExpr,
SrcRange: hcl.RangeBetween(next.Range, p.NextRange()),
})
case elseKeyword.TokenMatches(kw):
parts = append(parts, &templateEndCtrlToken{
Type: templateElse,
SrcRange: hcl.RangeBetween(next.Range, p.NextRange()),
})
case endifKeyword.TokenMatches(kw):
parts = append(parts, &templateEndCtrlToken{
Type: templateEndIf,
SrcRange: hcl.RangeBetween(next.Range, p.NextRange()),
})
case forKeyword.TokenMatches(kw):
var keyName, valName string
if p.Peek().Type != TokenIdent {
if !p.recovery {
diags = append(diags, &hcl.Diagnostic{
Severity: hcl.DiagError,
Summary: "Invalid 'for' directive",
Detail: "For directive requires variable name after 'for'.",
Subject: p.Peek().Range.Ptr(),
})
}
p.recover(TokenTemplateSeqEnd)
p.PopIncludeNewlines()
continue Token
}
valName = string(p.Read().Bytes)
if p.Peek().Type == TokenComma {
// What we just read was actually the key, then.
keyName = valName
p.Read() // eat comma
if p.Peek().Type != TokenIdent {
if !p.recovery {
diags = append(diags, &hcl.Diagnostic{
Severity: hcl.DiagError,
Summary: "Invalid 'for' directive",
Detail: "For directive requires value variable name after comma.",
Subject: p.Peek().Range.Ptr(),
})
}
p.recover(TokenTemplateSeqEnd)
p.PopIncludeNewlines()
continue Token
}
valName = string(p.Read().Bytes)
}
if !inKeyword.TokenMatches(p.Peek()) {
if !p.recovery {
diags = append(diags, &hcl.Diagnostic{
Severity: hcl.DiagError,
Summary: "Invalid 'for' directive",
Detail: "For directive requires 'in' keyword after names.",
Subject: p.Peek().Range.Ptr(),
})
}
p.recover(TokenTemplateSeqEnd)
p.PopIncludeNewlines()
continue Token
}
p.Read() // eat 'in' keyword
collExpr, collDiags := p.ParseExpression()
diags = append(diags, collDiags...)
parts = append(parts, &templateForToken{
KeyVar: keyName,
ValVar: valName,
CollExpr: collExpr,
SrcRange: hcl.RangeBetween(next.Range, p.NextRange()),
})
case endforKeyword.TokenMatches(kw):
parts = append(parts, &templateEndCtrlToken{
Type: templateEndFor,
SrcRange: hcl.RangeBetween(next.Range, p.NextRange()),
})
default:
if !p.recovery {
suggestions := []string{"if", "for", "else", "endif", "endfor"}
given := string(kw.Bytes)
suggestion := nameSuggestion(given, suggestions)
if suggestion != "" {
suggestion = fmt.Sprintf(" Did you mean %q?", suggestion)
}
diags = append(diags, &hcl.Diagnostic{
Severity: hcl.DiagError,
Summary: "Invalid template control keyword",
Detail: fmt.Sprintf("%q is not a valid template control keyword.%s", given, suggestion),
Subject: &kw.Range,
Context: hcl.RangeBetween(next.Range, kw.Range).Ptr(),
})
}
p.recover(TokenTemplateSeqEnd)
p.PopIncludeNewlines()
continue Token
}
close := p.Peek()
if close.Type != TokenTemplateSeqEnd {
if !p.recovery {
diags = append(diags, &hcl.Diagnostic{
Severity: hcl.DiagError,
Summary: fmt.Sprintf("Extra characters in %s marker", kw.Bytes),
Detail: "Expected a closing brace to end the sequence, but found extra characters.",
Subject: &close.Range,
Context: hcl.RangeBetween(startRange, close.Range).Ptr(),
})
}
p.recover(TokenTemplateSeqEnd)
} else {
p.Read() // eat closing brace
// If the closer is ~} then we want to eat any leading
// whitespace on the next token, if it turns out to be a
// literal token.
if len(close.Bytes) == 2 && close.Bytes[0] == '~' {
ltrimNext = true
}
}
p.PopIncludeNewlines()
default:
if !p.recovery {
diags = append(diags, &hcl.Diagnostic{
Severity: hcl.DiagError,
Summary: "Unterminated template string",
Detail: "No closing marker was found for the string.",
Subject: &next.Range,
Context: hcl.RangeBetween(startRange, next.Range).Ptr(),
})
}
final := p.recover(end)
endRange = final.Range
break Token
}
}
if len(parts) == 0 {
// If a sequence has no content, we'll treat it as if it had an
// empty string in it because that's what the user probably means
// if they write "" in configuration.
parts = append(parts, &templateLiteralToken{
Val: "",
SrcRange: hcl.Range{
// Range is the zero-character span immediately after the
// opening quote.
Filename: startRange.Filename,
Start: startRange.End,
End: startRange.End,
},
})
}
// Always end with an end token, so the parser can produce diagnostics
// about unclosed items with proper position information.
parts = append(parts, &templateEndToken{
SrcRange: endRange,
})
ret := &templateParts{
Tokens: parts,
SrcRange: hcl.RangeBetween(startRange, endRange),
}
return ret, diags
}
type templateParts struct {
Tokens []templateToken
SrcRange hcl.Range
}
// templateToken is a higher-level token that represents a single atom within
// the template language. Our template parsing first raises the raw token
// stream to a sequence of templateToken, and then transforms the result into
// an expression tree.
type templateToken interface {
templateToken() templateToken
}
type templateLiteralToken struct {
Val string
SrcRange hcl.Range
isTemplateToken
}
type templateInterpToken struct {
Expr Expression
SrcRange hcl.Range
isTemplateToken
}
type templateIfToken struct {
CondExpr Expression
SrcRange hcl.Range
isTemplateToken
}
type templateForToken struct {
KeyVar string // empty if ignoring key
ValVar string
CollExpr Expression
SrcRange hcl.Range
isTemplateToken
}
type templateEndCtrlType int
const (
templateEndIf templateEndCtrlType = iota
templateElse
templateEndFor
)
type templateEndCtrlToken struct {
Type templateEndCtrlType
SrcRange hcl.Range
isTemplateToken
}
func (t *templateEndCtrlToken) Name() string {
switch t.Type {
case templateEndIf:
return "endif"
case templateElse:
return "else"
case templateEndFor:
return "endfor"
default:
// should never happen
panic("invalid templateEndCtrlType")
}
}
type templateEndToken struct {
SrcRange hcl.Range
isTemplateToken
}
type isTemplateToken [0]int
func (t isTemplateToken) templateToken() templateToken {
return t
}