internal/gogrep: add support for $*_ in slice expr members (#284)

`$*_` inside a slice expression encodes an optional slice expression member: it could be nil or set to something that is non-nil.
quasilyte · Oct 15, 2021 · a0c5279 · a0c5279
1 parent af7b672
commit a0c5279
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Showing 4 changed files with 54 additions and 21 deletions.
diff --git a/internal/gogrep/compile.go b/internal/gogrep/compile.go
@@ -534,31 +534,31 @@ func (c *compiler) compileSliceExpr(n *ast.SliceExpr) {
 	switch {
 	case n.Low == nil && n.High == nil && !n.Slice3:
 		c.emitInstOp(opSliceExpr)
-		c.compileExpr(n.X)
+		c.compileOptExpr(n.X)
 	case n.Low != nil && n.High == nil && !n.Slice3:
 		c.emitInstOp(opSliceFromExpr)
-		c.compileExpr(n.X)
-		c.compileExpr(n.Low)
+		c.compileOptExpr(n.X)
+		c.compileOptExpr(n.Low)
 	case n.Low == nil && n.High != nil && !n.Slice3:
 		c.emitInstOp(opSliceToExpr)
-		c.compileExpr(n.X)
-		c.compileExpr(n.High)
+		c.compileOptExpr(n.X)
+		c.compileOptExpr(n.High)
 	case n.Low != nil && n.High != nil && !n.Slice3:
 		c.emitInstOp(opSliceFromToExpr)
-		c.compileExpr(n.X)
-		c.compileExpr(n.Low)
-		c.compileExpr(n.High)
+		c.compileOptExpr(n.X)
+		c.compileOptExpr(n.Low)
+		c.compileOptExpr(n.High)
 	case n.Low == nil && n.Slice3:
 		c.emitInstOp(opSliceToCapExpr)
-		c.compileExpr(n.X)
-		c.compileExpr(n.High)
-		c.compileExpr(n.Max)
+		c.compileOptExpr(n.X)
+		c.compileOptExpr(n.High)
+		c.compileOptExpr(n.Max)
 	case n.Low != nil && n.Slice3:
 		c.emitInstOp(opSliceFromToCapExpr)
-		c.compileExpr(n.X)
-		c.compileExpr(n.Low)
-		c.compileExpr(n.High)
-		c.compileExpr(n.Max)
+		c.compileOptExpr(n.X)
+		c.compileOptExpr(n.Low)
+		c.compileOptExpr(n.High)
+		c.compileOptExpr(n.Max)
 	default:
 		panic(c.errorf(n, "unexpected slice expr"))
 	}

diff --git a/internal/gogrep/compile_test.go b/internal/gogrep/compile_test.go
@@ -343,6 +343,19 @@ func TestCompileWildcard(t *testing.T) {
 			` •  • NodeSeq`,
 			` •  • End`,
 		},
+
+		`s[$*_:$*_]`: {
+			`SliceFromToExpr`,
+			` • Ident s`,
+			` • OptNode`,
+			` • OptNode`,
+		},
+
+		`s[$*_:]`: {
+			`SliceFromExpr`,
+			` • Ident s`,
+			` • OptNode`,
+		},
 	})
 
 	for i := range tests {

diff --git a/internal/gogrep/match.go b/internal/gogrep/match.go
@@ -251,24 +251,23 @@ func (m *matcher) matchNodeWithInst(inst instruction, n ast.Node) bool {
 		return ok && n.Low == nil && n.High == nil && m.matchNode(n.X)
 	case opSliceFromExpr:
 		n, ok := n.(*ast.SliceExpr)
-		return ok && n.Low != nil && n.High == nil && !n.Slice3 &&
+		return ok && n.High == nil && !n.Slice3 &&
 			m.matchNode(n.X) && m.matchNode(n.Low)
 	case opSliceToExpr:
 		n, ok := n.(*ast.SliceExpr)
-		return ok && n.Low == nil && n.High != nil && !n.Slice3 &&
+		return ok && n.Low == nil && !n.Slice3 &&
 			m.matchNode(n.X) && m.matchNode(n.High)
 	case opSliceFromToExpr:
 		n, ok := n.(*ast.SliceExpr)
-		return ok && n.Low != nil && n.High != nil && !n.Slice3 &&
+		return ok && !n.Slice3 &&
 			m.matchNode(n.X) && m.matchNode(n.Low) && m.matchNode(n.High)
 	case opSliceToCapExpr:
 		n, ok := n.(*ast.SliceExpr)
-		return ok && n.Low == nil && n.High != nil && n.Max != nil &&
+		return ok && n.Low == nil &&
 			m.matchNode(n.X) && m.matchNode(n.High) && m.matchNode(n.Max)
 	case opSliceFromToCapExpr:
 		n, ok := n.(*ast.SliceExpr)
-		return ok && n.Low != nil && n.High != nil && n.Max != nil &&
-			m.matchNode(n.X) && m.matchNode(n.Low) && m.matchNode(n.High) && m.matchNode(n.Max)
+		return ok && m.matchNode(n.X) && m.matchNode(n.Low) && m.matchNode(n.High) && m.matchNode(n.Max)
 
 	case opIndexExpr:
 		n, ok := n.(*ast.IndexExpr)

diff --git a/internal/gogrep/match_test.go b/internal/gogrep/match_test.go
@@ -167,10 +167,12 @@ func TestMatch(t *testing.T) {
 		{`x[:y]`, 0, `z[:y]`},
 		{`x[:y]`, 0, `x[:y:z]`},
 		{`$x[:$y]`, 1, `a[:1]`},
+		{`$x[:$y]`, 0, `a[:]`},
 		{`x[y:]`, 1, `x[y:]`},
 		{`x[y:]`, 0, `z[y:]`},
 		{`x[y:]`, 0, `x[z:]`},
 		{`$x[$y:]`, 1, `a[1:]`},
+		{`$x[$y:]`, 0, `a[:]`},
 		{`x[y:z]`, 1, `x[y:z]`},
 		{`x[y:z]`, 0, `_[y:z]`},
 		{`x[y:z]`, 0, `x[_:z]`},
@@ -189,6 +191,25 @@ func TestMatch(t *testing.T) {
 		{`x[5:y:z]`, 0, `x[5:y:_]`},
 		{`x[5:y:z]`, 0, `x[0:y:z]`},
 		{`x[5:y:z]`, 0, `x[5:y]`},
+		{`x[$*_:]`, 1, `x[:]`},
+		{`x[$*_:]`, 1, `x[1:]`},
+		{`x[$*_:]`, 0, `x[1:2]`},
+		{`x[:$*_]`, 1, `x[:]`},
+		{`x[:$*_]`, 1, `x[:2]`},
+		{`x[:$*_]`, 0, `x[1:2]`},
+		{`x[$*_:$*_]`, 1, `x[:]`},
+		{`x[$*_:$*_]`, 1, `x[1:]`},
+		{`x[$*_:$*_]`, 1, `x[:2]`},
+		{`x[$*_:$*_]`, 1, `x[1:2]`},
+		{`x[$*_:$*_]`, 0, `x[1:2:2]`},
+		{`x[$*_:$*_:$*_]`, 1, `x[:]`},
+		{`x[$*_:$*_:$*_]`, 1, `x[1:]`},
+		{`x[$*_:$*_:$*_]`, 1, `x[:2]`},
+		{`x[$*_:$*_:$*_]`, 1, `x[1:2]`},
+		{`x[$*_:$*_:$*_]`, 1, `x[1:2:2]`},
+		{`x[$*y:$*y]`, 1, `x[:]`},
+		{`x[$*y:$*y]`, 1, `x[1:1]`},
+		{`x[$*y:$*y]`, 0, `x[1:0]`},
 
 		// Composite literals.
 		{`[]int{1, $x, $x}`, 1, `[]int{1, 2, 2}`},