linter: new rule about deprecated string interpolation (#1218)

docs/checkers_doc.md

@@ -4,7 +4,7 @@
 
 | Total checks | Checks enabled by default | Disabled checks by default | Autofixable checks |
 | ------------ | ------------------------- | -------------------------- | ------------------ |
-| 104           | 86                        | 18                         | 14                 |
+| 105           | 87                        | 18                         | 14                 |
 
 ## Table of contents
  - Enabled by default
@@ -75,6 +75,7 @@
    - [`stdInterface` checker](#stdinterface-checker)
    - [`strangeCast` checker](#strangecast-checker)
    - [`strictCmp` checker](#strictcmp-checker)
+   - [`stringInterpolationDeprecated` checker](#stringinterpolationdeprecated-checker)
    - [`stripTags` checker](#striptags-checker)
    - [`switchEmpty` checker](#switchempty-checker)
    - [`switchSimplify` checker](#switchsimplify-checker)
@@ -1183,7 +1184,7 @@ interface Iface {
 
 #### Description
 
-Report not nullable param can be null.
+Report not nullable param with explicit null default value.
 
 #### Non-compliant code:
 ```php
@@ -1471,6 +1472,24 @@ in_array("what", $s, true)
 <p><br></p>
 
 
+### `stringInterpolationDeprecated` checker
+
+#### Description
+
+Report deprecated string interpolation style
+
+#### Non-compliant code:
+```php
+${variable}
+```
+
+#### Compliant code:
+```php
+{$variable}
+```
+<p><br></p>
+
+
 ### `stripTags` checker
 
 #### Description

src/linter/block_linter.go

@@ -24,6 +24,10 @@ type blockLinter struct {
 
 func (b *blockLinter) enterNode(n ir.Node) {
 	switch n := n.(type) {
+
+	case *ir.Encapsed:
+		b.checkStringInterpolationDeprecation(n)
+
 	case *ir.Assign:
 		b.checkAssign(n)
 
@@ -207,6 +211,18 @@ func (b *blockLinter) enterNode(n ir.Node) {
 	}
 }
 
+func (b *blockLinter) checkStringInterpolationDeprecation(str *ir.Encapsed) {
+	for _, item := range str.Parts {
+		variable, ok := item.(*ir.SimpleVar)
+		if ok {
+			if variable.IdentifierTkn.Value[0] != '$' {
+				b.report(str, LevelWarning, "stringInterpolationDeprecated", "use {$variable} instead ${variable}")
+				break
+			}
+		}
+	}
+}
+
 func (b *blockLinter) checkUnaryPlus(n *ir.UnaryPlusExpr) {
 	val := constfold.Eval(b.classParseState(), n.Expr)
 	if val.IsValid() {

src/linter/report.go

@@ -618,6 +618,15 @@ g();`,
 }`,
 		},
 
+		{
+			Name:     "stringInterpolationDeprecated",
+			Default:  true,
+			Quickfix: false,
+			Comment:  `Report deprecated string interpolation style`,
+			Before:   `${variable}`,
+			After:    `{$variable}`,
+		},
+
 		{
 			Name:     "misspellName",
 			Default:  true,

src/tests/checkers/string_interpolation_test.go

@@ -0,0 +1,50 @@
+package checkers
+
+import (
+	"testing"
+
+	"github.com/VKCOM/noverify/src/linttest"
+)
+
+func TestInterpolationDeprecated1(t *testing.T) {
+	test := linttest.NewSuite(t)
+	test.AddFile(`<?php
+declare(strict_types = 1);
+
+$name = 'PHP';
+
+echo "Hello ${name}";
+`)
+	test.Expect = []string{
+		`stringInterpolationDeprecated: use {$variable} instead ${variable}`,
+	}
+	test.RunAndMatch()
+}
+
+func TestInterpolationDeprecated2(t *testing.T) {
+	test := linttest.NewSuite(t)
+	test.AddFile(`<?php
+declare(strict_types = 1);
+
+$name = 'PHP';
+
+echo "Hello {$name}";
+`)
+	test.RunAndMatch()
+}
+
+func TestInterpolationDeprecated3(t *testing.T) {
+	test := linttest.NewSuite(t)
+	test.AddFile(`<?php
+declare(strict_types = 1);
+
+$name = 'PHP';
+$lang = 'language';
+
+echo "Hello {$name} ${lang}";
+`)
+	test.Expect = []string{
+		`stringInterpolationDeprecated: use {$variable} instead ${variable}`,
+	}
+	test.RunAndMatch()
+}