Namespaced functions

hclsyntax/expression.go

@@ -6,6 +6,7 @@ package hclsyntax
 import (
 	"fmt"
 	"sort"
+	"strings"
 	"sync"
 
 	"github.com/hashicorp/hcl/v2"
@@ -251,6 +252,67 @@ func (e *FunctionCallExpr) Value(ctx *hcl.EvalContext) (cty.Value, hcl.Diagnosti
 			}
 		}
 
+		// For historical reasons, we represent namespaced function names
+		// as strings with :: separating the names. If this was an attempt
+		// to call a namespaced function then we'll try to distinguish
+		// between an invalid namespace or an invalid name within a valid
+		// namespace in order to give the user better feedback about what
+		// is wrong.
+		//
+		// The parser guarantees that a function name will always
+		// be a series of valid identifiers separated by "::" with no
+		// other content, so we can be relatively unforgiving in our processing
+		// here.
+		if sepIdx := strings.LastIndex(e.Name, "::"); sepIdx != -1 {
+			namespace := e.Name[:sepIdx+2]
+			name := e.Name[sepIdx+2:]
+
+			avail := make([]string, 0, len(ctx.Functions))
+			for availName := range ctx.Functions {
+				if strings.HasPrefix(availName, namespace) {
+					avail = append(avail, availName)
+				}
+			}
+
+			if len(avail) == 0 {
+				// TODO: Maybe use nameSuggestion for the other available
+				// namespaces? But that'd require us to go scan the function
+				// table again, so we'll wait to see if it's really warranted.
+				// For now, we're assuming people are more likely to misremember
+				// the function names than the namespaces, because in many
+				// applications there will be relatively few namespaces compared
+				// to the number of distinct functions.
+				return cty.DynamicVal, hcl.Diagnostics{
+					{
+						Severity:    hcl.DiagError,
+						Summary:     "Call to unknown function",
+						Detail:      fmt.Sprintf("There are no functions in namespace %q.", namespace),
+						Subject:     &e.NameRange,
+						Context:     e.Range().Ptr(),
+						Expression:  e,
+						EvalContext: ctx,
+					},
+				}
+			} else {
+				suggestion := nameSuggestion(name, avail)
+				if suggestion != "" {
+					suggestion = fmt.Sprintf(" Did you mean %s%s?", namespace, suggestion)
+				}
+
+				return cty.DynamicVal, hcl.Diagnostics{
+					{
+						Severity:    hcl.DiagError,
+						Summary:     "Call to unknown function",
+						Detail:      fmt.Sprintf("There is no function named %q in namespace %s.%s", name, namespace, suggestion),
+						Subject:     &e.NameRange,
+						Context:     e.Range().Ptr(),
+						Expression:  e,
+						EvalContext: ctx,
+					},
+				}
+			}
+		}
+
 		avail := make([]string, 0, len(ctx.Functions))
 		for name := range ctx.Functions {
 			avail = append(avail, name)

hclsyntax/expression_test.go

@@ -342,6 +342,56 @@ upper(
 			cty.DynamicVal,
 			0,
 		},
+		{
+			`foo::upper("foo")`,
+			&hcl.EvalContext{
+				Functions: map[string]function.Function{
+					"foo::upper": stdlib.UpperFunc,
+				},
+			},
+			cty.StringVal("FOO"),
+			0,
+		},
+		{
+			`foo :: upper("foo")`, // spaces are non-idomatic, but valid
+			&hcl.EvalContext{
+				Functions: map[string]function.Function{
+					"foo::upper": stdlib.UpperFunc,
+				},
+			},
+			cty.StringVal("FOO"),
+			0,
+		},
+		{
+			`::upper("foo")`, // :: is still not a valid identifier
+			&hcl.EvalContext{
+				Functions: map[string]function.Function{
+					"::upper": stdlib.UpperFunc,
+				},
+			},
+			cty.DynamicVal,
+			1,
+		},
+		{
+			`double::::upper("foo")`, // missing name after ::
+			&hcl.EvalContext{
+				Functions: map[string]function.Function{
+					"double::::upper": stdlib.UpperFunc,
+				},
+			},
+			cty.NilVal,
+			1,
+		},
+		{
+			`missing::("foo")`, // missing name after ::
+			&hcl.EvalContext{
+				Functions: map[string]function.Function{
+					"missing::": stdlib.UpperFunc,
+				},
+			},
+			cty.NilVal,
+			1,
+		},
 		{
 			`misbehave()`,
 			&hcl.EvalContext{
@@ -2174,8 +2224,12 @@ EOT
 	for _, test := range tests {
 		t.Run(test.input, func(t *testing.T) {
 			expr, parseDiags := ParseExpression([]byte(test.input), "", hcl.Pos{Line: 1, Column: 1, Byte: 0})
+			var got cty.Value
+			var valDiags hcl.Diagnostics
 
-			got, valDiags := expr.Value(test.ctx)
+			if expr != nil {
+				got, valDiags = expr.Value(test.ctx)
+			}
 
 			diagCount := len(parseDiags) + len(valDiags)
 

hclsyntax/generate.go

@@ -9,4 +9,4 @@ package hclsyntax
 //go:generate gofmt -w scan_tokens.go
 //go:generate ragel -Z scan_string_lit.rl
 //go:generate gofmt -w scan_string_lit.go
-//go:generate stringer -type TokenType -output token_type_string.go
+//go:generate go run golang.org/x/tools/cmd/stringer -type TokenType -output token_type_string.go

hclsyntax/parser.go

@@ -999,7 +999,7 @@ func (p *parser) parseExpressionTerm() (Expression, hcl.Diagnostics) {
 	case TokenIdent:
 		tok := p.Read() // eat identifier token
 
-		if p.Peek().Type == TokenOParen {
+		if p.Peek().Type == TokenOParen || p.Peek().Type == TokenDoubleColon {
 			return p.finishParsingFunctionCall(tok)
 		}
 
@@ -1145,16 +1145,57 @@ func (p *parser) numberLitValue(tok Token) (cty.Value, hcl.Diagnostics) {
 
 // finishParsingFunctionCall parses a function call assuming that the function
 // name was already read, and so the peeker should be pointing at the opening
-// parenthesis after the name.
+// parenthesis after the name, or at the double-colon after the initial
+// function scope name.
 func (p *parser) finishParsingFunctionCall(name Token) (Expression, hcl.Diagnostics) {
+	var diags hcl.Diagnostics
+
 	openTok := p.Read()
-	if openTok.Type != TokenOParen {
+	if openTok.Type != TokenOParen && openTok.Type != TokenDoubleColon {
 		// should never happen if callers behave
-		panic("finishParsingFunctionCall called with non-parenthesis as next token")
+		panic("finishParsingFunctionCall called with unsupported next token")
+	}
+
+	nameStr := string(name.Bytes)
+	for openTok.Type == TokenDoubleColon {
+		nextName := p.Read()
+		if nextName.Type != TokenIdent {
+			diags = append(diags, &hcl.Diagnostic{
+				Severity: hcl.DiagError,
+				Summary:  "Missing function name",
+				Detail:   "Function scope resolution symbol :: must be followed by a function name in this scope.",
+				Subject:  &nextName.Range,
+				Context:  hcl.RangeBetween(name.Range, nextName.Range).Ptr(),
+			})
+			p.recoverOver(TokenOParen)
+			return nil, diags
+		}
+
+		// Initial versions of HCLv2 didn't support function namespaces, and
+		// so for backward compatibility we just treat namespaced functions
+		// as weird names with "::" separators in them, saved as a string
+		// to keep the API unchanged. FunctionCallExpr also has some special
+		// handling of names containing :: when referring to a function that
+		// doesn't exist in EvalContext, to return better error messages
+		// when namespaces are used incorrectly.
+		nameStr = nameStr + "::" + string(nextName.Bytes)
+
+		openTok = p.Read()
+	}
+
+	if openTok.Type != TokenOParen {
+		diags = append(diags, &hcl.Diagnostic{
+			Severity: hcl.DiagError,
+			Summary:  "Missing open parenthesis",
+			Detail:   "Function selector must be followed by an open parenthesis to begin the function call.",
+			Subject:  &openTok.Range,
+			Context:  hcl.RangeBetween(name.Range, openTok.Range).Ptr(),
+		})
+		p.recoverOver(TokenOParen)
+		return nil, diags
 	}
 
 	var args []Expression
-	var diags hcl.Diagnostics
 	var expandFinal bool
 	var closeTok Token
 
@@ -1245,7 +1286,7 @@ Token:
 	p.PopIncludeNewlines()
 
 	return &FunctionCallExpr{
-		Name: string(name.Bytes),
+		Name: nameStr,
 		Args: args,
 
 		ExpandFinal: expandFinal,