opa build -t wasm|plan: fail on unmatched entrypoints

Fixes #3957

Signed-off-by: Anders Eknert <anders@eknert.com>

ast/builtins.go

@@ -941,8 +941,8 @@ var RegexFind = &Builtin{
 // GlobsMatch takes two strings regexp-style strings and evaluates to true if their
 // intersection matches a non-empty set of non-empty strings.
 // Examples:
-//  - "a.a." and ".b.b" -> true.
-//  - "[a-z]*" and [0-9]+" -> not true.
+//   - "a.a." and ".b.b" -> true.
+//   - "[a-z]*" and [0-9]+" -> not true.
 var GlobsMatch = &Builtin{
 	Name: "regex.globs_match",
 	Description: `Checks if the intersection of two glob-style regular expressions matches a non-empty set of non-empty strings.

compile/compile.go

@@ -418,7 +418,7 @@ func (c *Compiler) optimize(ctx context.Context) error {
 	return nil
 }
 
-func (c *Compiler) compilePlan(ctx context.Context) error {
+func (c *Compiler) compilePlan(context.Context) error {
 
 	// Lazily compile the modules if needed. If optimizations were run, the
 	// AST compiler will not be set because the default target does not require it.
@@ -464,6 +464,7 @@ func (c *Compiler) compilePlan(ctx context.Context) error {
 	// Create query sets for each of the entrypoints.
 	resultSym := ast.NewTerm(resultVar)
 	queries := make([]planner.QuerySet, len(c.entrypointrefs))
+	var unmappedEntrypoints []string
 
 	for i := range c.entrypointrefs {
 
@@ -474,13 +475,22 @@ func (c *Compiler) compilePlan(ctx context.Context) error {
 			return err
 		}
 
+		if len(c.compiler.GetRules(c.entrypointrefs[i].Value.(ast.Ref))) == 0 {
+			unmappedEntrypoints = append(unmappedEntrypoints, c.entrypoints[i])
+		}
+
 		queries[i] = planner.QuerySet{
 			Name:          c.entrypoints[i],
 			Queries:       []ast.Body{compiled},
 			RewrittenVars: qc.RewrittenVars(),
 		}
 	}
 
+	if len(unmappedEntrypoints) > 0 {
+		return fmt.Errorf("entrypoint %q does not refer to a rule or policy decision", unmappedEntrypoints[0])
+
+	}
+
 	// Prepare modules and builtins for the planner.
 	modules := []*ast.Module{}
 	for _, module := range c.compiler.Modules {
@@ -503,7 +513,7 @@ func (c *Compiler) compilePlan(ctx context.Context) error {
 		return err
 	}
 
-	// dump policy IR (if "debug" wasn't requested, debug.Witer will discard it)
+	// dump policy IR (if "debug" wasn't requested, debug.Writer will discard it)
 	err = ir.Pretty(c.debug.Writer(), policy)
 	if err != nil {
 		return err

compile/compile_test.go

@@ -55,6 +55,11 @@ func TestCompilerInitErrors(t *testing.T) {
 			c:    New().WithTarget("wasm"),
 			want: errors.New("wasm compilation requires at least one entrypoint"),
 		},
+		{
+			note: "plan compilation requires at least one entrypoint",
+			c:    New().WithTarget("plan"),
+			want: errors.New("plan compilation requires at least one entrypoint"),
+		},
 	}
 
 	for _, tc := range tests {
@@ -781,6 +786,41 @@ func TestCompilerPlanTargetPruneUnused(t *testing.T) {
 	})
 }
 
+func TestCompilerPlanTargetUnmatchedEntrypoints(t *testing.T) {
+	files := map[string]string{
+		"test.rego": `package test
+
+		p := 7
+		q := p + 1`,
+	}
+
+	test.WithTempFS(files, func(root string) {
+
+		compiler := New().WithPaths(root).WithTarget("plan").WithEntrypoints("test/p", "test/q", "test/no")
+		err := compiler.Build(context.Background())
+		if err == nil {
+			t.Error("expected error from unmatched entrypoint")
+		}
+		expectError := "entrypoint \"test/no\" does not refer to a rule or policy decision"
+		if err.Error() != expectError {
+			t.Errorf("expected error %s, got: %s", expectError, err.Error())
+		}
+	})
+
+	test.WithTempFS(files, func(root string) {
+
+		compiler := New().WithPaths(root).WithTarget("plan").WithEntrypoints("foo", "foo.bar", "test/no")
+		err := compiler.Build(context.Background())
+		if err == nil {
+			t.Error("expected error from unmatched entrypoints")
+		}
+		expectError := "entrypoint \"foo\" does not refer to a rule or policy decision"
+		if err.Error() != expectError {
+			t.Errorf("expected error %s, got: %s", expectError, err.Error())
+		}
+	})
+}
+
 func TestCompilerSetRevision(t *testing.T) {
 	files := map[string]string{
 		"test.rego": `package test