zclsyntax: template "for" construct

zcl/zclsyntax/expression_template.go

@@ -85,6 +85,86 @@ func (e *TemplateExpr) StartRange() zcl.Range {
 	return e.Parts[0].StartRange()
 }
 
+// TemplateJoinExpr is used to convert tuples of strings produced by template
+// constructs (i.e. for loops) into flat strings, by converting the values
+// tos strings and joining them. This AST node is not used directly; it's
+// produced as part of the AST of a "for" loop in a template.
+type TemplateJoinExpr struct {
+	Tuple Expression
+}
+
+func (e *TemplateJoinExpr) walkChildNodes(w internalWalkFunc) {
+	e.Tuple = w(e.Tuple).(Expression)
+}
+
+func (e *TemplateJoinExpr) Value(ctx *zcl.EvalContext) (cty.Value, zcl.Diagnostics) {
+	tuple, diags := e.Tuple.Value(ctx)
+
+	if tuple.IsNull() {
+		// This indicates a bug in the code that constructed the AST.
+		panic("TemplateJoinExpr got null tuple")
+	}
+	if tuple.Type() == cty.DynamicPseudoType {
+		return cty.UnknownVal(cty.String), diags
+	}
+	if !tuple.Type().IsTupleType() {
+		// This indicates a bug in the code that constructed the AST.
+		panic("TemplateJoinExpr got non-tuple tuple")
+	}
+	if !tuple.IsKnown() {
+		return cty.UnknownVal(cty.String), diags
+	}
+
+	buf := &bytes.Buffer{}
+	it := tuple.ElementIterator()
+	for it.Next() {
+		_, val := it.Element()
+
+		if val.IsNull() {
+			diags = append(diags, &zcl.Diagnostic{
+				Severity: zcl.DiagError,
+				Summary:  "Invalid template interpolation value",
+				Detail: fmt.Sprintf(
+					"An iteration result is null. Cannot include a null value in a string template.",
+				),
+				Subject: e.Range().Ptr(),
+			})
+			continue
+		}
+		if val.Type() == cty.DynamicPseudoType {
+			return cty.UnknownVal(cty.String), diags
+		}
+		strVal, err := convert.Convert(val, cty.String)
+		if err != nil {
+			diags = append(diags, &zcl.Diagnostic{
+				Severity: zcl.DiagError,
+				Summary:  "Invalid template interpolation value",
+				Detail: fmt.Sprintf(
+					"Cannot include one of the interpolation results into the string template: %s.",
+					err.Error(),
+				),
+				Subject: e.Range().Ptr(),
+			})
+			continue
+		}
+		if !val.IsKnown() {
+			return cty.UnknownVal(cty.String), diags
+		}
+
+		buf.WriteString(strVal.AsString())
+	}
+
+	return cty.StringVal(buf.String()), diags
+}
+
+func (e *TemplateJoinExpr) Range() zcl.Range {
+	return e.Tuple.Range()
+}
+
+func (e *TemplateJoinExpr) StartRange() zcl.Range {
+	return e.Tuple.StartRange()
+}
+
 // TemplateWrapExpr is used instead of a TemplateExpr when a template
 // consists _only_ of a single interpolation sequence. In that case, the
 // template's result is the single interpolation's result, verbatim with

zcl/zclsyntax/expression_template_test.go

@@ -171,6 +171,52 @@ trim`,
 			cty.UnknownVal(cty.String),
 			2, // "of" is not a valid control keyword, and "endif" is therefore also unexpected
 		},
+		{
+			`%{ for v in ["a", "b", "c"] }${v}%{ endfor }`,
+			nil,
+			cty.StringVal("abc"),
+			0,
+		},
+		{
+			`%{ for v in ["a", "b", "c"] } ${v} %{ endfor }`,
+			nil,
+			cty.StringVal(" a  b  c "),
+			0,
+		},
+		{
+			`%{ for v in ["a", "b", "c"] ~} ${v} %{~ endfor }`,
+			nil,
+			cty.StringVal("abc"),
+			0,
+		},
+		{
+			`%{ for v in [] }${v}%{ endfor }`,
+			nil,
+			cty.StringVal(""),
+			0,
+		},
+		{
+			`%{ for i, v in ["a", "b", "c"] }${i}${v}%{ endfor }`,
+			nil,
+			cty.StringVal("0a1b2c"),
+			0,
+		},
+		{
+			`%{ for k, v in {"A" = "a", "B" = "b", "C" = "c"} }${k}${v}%{ endfor }`,
+			nil,
+			cty.StringVal("AaBbCc"),
+			0,
+		},
+		{
+			`%{ for v in ["a", "b", "c"] }${v}${nl}%{ endfor }`,
+			&zcl.EvalContext{
+				Variables: map[string]cty.Value{
+					"nl": cty.StringVal("\n"),
+				},
+			},
+			cty.StringVal("a\nb\nc\n"),
+			0,
+		},
 	}
 
 	for _, test := range tests {

zcl/zclsyntax/expression_vars.go

@@ -55,6 +55,10 @@ func (e *TemplateExpr) Variables() []zcl.Traversal {
 	return Variables(e)
 }
 
+func (e *TemplateJoinExpr) Variables() []zcl.Traversal {
+	return Variables(e)
+}
+
 func (e *TemplateWrapExpr) Variables() []zcl.Traversal {
 	return Variables(e)
 }

zcl/zclsyntax/parser_template.go

@@ -240,6 +240,103 @@ Token:
 	}, diags
 }
 
+func (p *templateParser) parseFor() (Expression, zcl.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 zcl.Diagnostics
+	var endforRange zcl.Range
+
+Token:
+	for {
+		next := p.Peek()
+		if end, isEnd := next.(*templateEndToken); isEnd {
+			diags = append(diags, &zcl.Diagnostic{
+				Severity: zcl.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, &zcl.Diagnostic{
+					Severity: zcl.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, &zcl.Diagnostic{
+					Severity: zcl.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: zcl.Range{
+				Filename: openFor.SrcRange.Filename,
+				Start:    openFor.SrcRange.End,
+				End:      openFor.SrcRange.End,
+			},
+		})
+	}
+
+	contentExpr := &TemplateExpr{
+		Parts:    contentExprs,
+		SrcRange: zcl.RangeBetween(contentExprs[0].Range(), contentExprs[len(contentExprs)-1].Range()),
+	}
+
+	forExpr := &ForExpr{
+		KeyVar: openFor.KeyVar,
+		ValVar: openFor.ValVar,
+
+		CollExpr: openFor.CollExpr,
+		ValExpr:  contentExpr,
+
+		SrcRange:   zcl.RangeBetween(openFor.SrcRange, endforRange),
+		OpenRange:  openFor.SrcRange,
+		CloseRange: endforRange,
+	}
+
+	return &TemplateJoinExpr{
+		Tuple: forExpr,
+	}, diags
+}
+
 func (p *templateParser) Peek() templateToken {
 	return p.Tokens[p.pos]
 }
@@ -354,8 +451,8 @@ Token:
 				if !p.recovery {
 					diags = append(diags, &zcl.Diagnostic{
 						Severity: zcl.DiagError,
-						Summary:  "Invalid template control keyword",
-						Detail:   "A template control keyword (\"if\", \"for\", etc) is expected at the beginning of a !{ sequence.",
+						Summary:  "Invalid template directive",
+						Detail:   "A template directive keyword (\"if\", \"for\", etc) is expected at the beginning of a !{ sequence.",
 						Subject:  &kw.Range,
 						Context:  zcl.RangeBetween(next.Range, kw.Range).Ptr(),
 					})
@@ -388,6 +485,77 @@ Token:
 					SrcRange: zcl.RangeBetween(next.Range, p.NextRange()),
 				})
 
+			case forKeyword.TokenMatches(kw):
+				var keyName, valName string
+				if p.Peek().Type != TokenIdent {
+					if !p.recovery {
+						diags = append(diags, &zcl.Diagnostic{
+							Severity: zcl.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, &zcl.Diagnostic{
+								Severity: zcl.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, &zcl.Diagnostic{
+							Severity: zcl.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: zcl.RangeBetween(next.Range, p.NextRange()),
+				})
+
+			case endforKeyword.TokenMatches(kw):
+				parts = append(parts, &templateEndCtrlToken{
+					Type:     templateEndFor,
+					SrcRange: zcl.RangeBetween(next.Range, p.NextRange()),
+				})
+
 			default:
 				if !p.recovery {
 					suggestions := []string{"if", "for", "else", "endif", "endfor"}