Add idlgen run tests

Adds test coverage for //tools/src/cmd/idlgen's run function. More
specific tests for underlying helper functions will be added in
follow-up CLs.

Also fixes a found issue where there was code to support outputting to
stdout, but it was unreachable since the --output argument was treated
as required.

Bug: 344014313
Change-Id: Ibb341bf73ad107ed98f457ca44202031f0c474b4
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/282857
Reviewed-by: dan sinclair <[email protected]>
Auto-Submit: Brian Sheedy <[email protected]>
Commit-Queue: Brian Sheedy <[email protected]>

Author: bsheedy-work

tools/src/cmd/idlgen/main.go

@@ -75,7 +75,7 @@ func run(args []string, osWrapper oswrapper.OSWrapper) error {
 	idlFiles := flagSet.Args()
 
 	// Check all required arguments are provided
-	if templatePath == "" || outputPath == "" || len(idlFiles) == 0 {
+	if templatePath == "" || len(idlFiles) == 0 {
 		return showUsage()
 	}
 

tools/src/cmd/idlgen/main_test.go

@@ -0,0 +1,193 @@
+// Copyright 2026 The Dawn & Tint Authors
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+// 1. Redistributions of source code must retain the above copyright notice, this
+//    list of conditions and the following disclaimer.
+//
+// 2. Redistributions in binary form must reproduce the above copyright notice,
+//    this list of conditions and the following disclaimer in the documentation
+//    and/or other materials provided with the distribution.
+//
+// 3. Neither the name of the copyright holder nor the names of its
+//    contributors may be used to endorse or promote products derived from
+//    this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package main
+
+import (
+	"testing"
+
+	"dawn.googlesource.com/dawn/tools/src/oswrapper"
+	"github.com/stretchr/testify/require"
+)
+
+func TestRun_MissingArgs(t *testing.T) {
+	tests := []struct {
+		name string
+		args []string
+	}{
+		{
+			name: "No args",
+			args: []string{},
+		},
+		{
+			name: "Missing template",
+			args: []string{"--output=out.go", "input.idl"},
+		},
+		{
+			name: "Missing input file",
+			args: []string{"--template=tmpl.go", "--output=out.go"},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			wrapper := oswrapper.CreateFSTestOSWrapper()
+			err := run(tt.args, wrapper)
+			require.ErrorContains(t, err, "idlgen is a tool used to generate code")
+		})
+	}
+}
+
+func TestRun_OutputToStdout(t *testing.T) {
+	wrapper := oswrapper.CreateFSTestOSWrapper()
+	require.NoError(t, wrapper.WriteFile("template.tmpl", []byte("{{.}}"), 0644))
+	require.NoError(t, wrapper.WriteFile("test.idl", []byte("interface Test {}; interface GPUDevice {};"), 0644))
+
+	args := []string{"--template=template.tmpl", "test.idl"}
+	err := run(args, wrapper)
+	require.NoError(t, err)
+}
+
+func TestRun_OutputToFile(t *testing.T) {
+	wrapper := oswrapper.CreateFSTestOSWrapper()
+	require.NoError(t, wrapper.WriteFile("template.tmpl", []byte("{{range .Declarations}}{{.Name}} {{end}}"), 0644))
+	require.NoError(t, wrapper.WriteFile("test.idl", []byte("interface Test {}; interface GPUDevice {};"), 0644))
+
+	outputPath := "subdir/out.txt"
+	args := []string{"--template=template.tmpl", "--output=" + outputPath, "test.idl"}
+	err := run(args, wrapper)
+	require.NoError(t, err)
+
+	// Verify file exists and has content
+	content, err := wrapper.ReadFile(outputPath)
+	require.NoError(t, err)
+	require.Contains(t, string(content), "Test GPUDevice")
+}
+
+func TestRun_OutputDirectoryCreationFailure(t *testing.T) {
+	wrapper := oswrapper.CreateFSTestOSWrapper()
+	require.NoError(t, wrapper.WriteFile("template.tmpl", []byte("{{.}}"), 0644))
+	require.NoError(t, wrapper.WriteFile("test.idl", []byte("interface Test {};"), 0644))
+
+	// Create a file named "subdir" to block directory creation
+	require.NoError(t, wrapper.WriteFile("subdir", []byte("i am a file"), 0644))
+
+	outputPath := "subdir/out.txt"
+	args := []string{"--template=template.tmpl", "--output=" + outputPath, "test.idl"}
+	err := run(args, wrapper)
+	require.Error(t, err)
+	require.ErrorContains(t, err, "failed to create output directory")
+}
+
+func TestRun_OutputFileCreationFailure(t *testing.T) {
+	wrapper := oswrapper.CreateFSTestOSWrapper()
+	require.NoError(t, wrapper.WriteFile("template.tmpl", []byte("{{.}}"), 0644))
+	require.NoError(t, wrapper.WriteFile("test.idl", []byte("interface Test {};"), 0644))
+
+	outputPath := "out.txt"
+	// Create a directory at the output path to cause Create to fail
+	require.NoError(t, wrapper.Mkdir(outputPath, 0755))
+
+	args := []string{"--template=template.tmpl", "--output=" + outputPath, "test.idl"}
+	err := run(args, wrapper)
+	require.Error(t, err)
+	require.ErrorContains(t, err, "failed to open output file")
+}
+
+func TestRun_TemplateReadFailure(t *testing.T) {
+	wrapper := oswrapper.CreateFSTestOSWrapper()
+	// Do not create the template file
+
+	require.NoError(t, wrapper.WriteFile("test.idl", []byte("interface Test {};"), 0644))
+
+	args := []string{"--template=template.tmpl", "test.idl"}
+	err := run(args, wrapper)
+	require.ErrorContains(t, err, "failed to open template file")
+}
+
+func TestRun_IDLReadFailure(t *testing.T) {
+	wrapper := oswrapper.CreateFSTestOSWrapper()
+	require.NoError(t, wrapper.WriteFile("template.tmpl", []byte("{{.}}"), 0644))
+
+	// Provide a non-existent IDL file
+	args := []string{"--template=template.tmpl", "missing.idl"}
+	err := run(args, wrapper)
+	require.ErrorContains(t, err, "failed to open file 'missing.idl'")
+}
+
+func TestRun_IDLParseFailure(t *testing.T) {
+	wrapper := oswrapper.CreateFSTestOSWrapper()
+	require.NoError(t, wrapper.WriteFile("template.tmpl", []byte("{{.}}"), 0644))
+	// Provide invalid IDL content
+	require.NoError(t, wrapper.WriteFile("invalid.idl", []byte("this is definitely not valid idl"), 0644))
+
+	args := []string{"--template=template.tmpl", "invalid.idl"}
+	err := run(args, wrapper)
+	require.ErrorContains(t, err, "errors found while parsing invalid.idl")
+}
+
+func TestRun_TemplateParseFailure(t *testing.T) {
+	wrapper := oswrapper.CreateFSTestOSWrapper()
+	// Provide invalid template content (unclosed action)
+	require.NoError(t, wrapper.WriteFile("invalid.tmpl", []byte("{{.Name"), 0644))
+	require.NoError(t, wrapper.WriteFile("test.idl", []byte("interface Test {}; interface GPUDevice {};"), 0644))
+
+	args := []string{"--template=invalid.tmpl", "test.idl"}
+	err := run(args, wrapper)
+	require.ErrorContains(t, err, "failed to parse template file")
+}
+
+func TestRun_SuccessfulExecution(t *testing.T) {
+	wrapper := oswrapper.CreateFSTestOSWrapper()
+
+	// A simple template that iterates over declarations and prints their names
+	templateContent := `{{range .Declarations}}{{.Name}};{{end}}`
+	require.NoError(t, wrapper.WriteFile("template.tmpl", []byte(templateContent), 0644))
+
+	// A simple IDL file. GPUDevice is required to avoid a panic in the patch function.
+	idlContent := `
+		interface MyInterface {
+			void myMethod();
+		};
+		interface GPUDevice {};
+	`
+	require.NoError(t, wrapper.WriteFile("test.idl", []byte(idlContent), 0644))
+
+	outputPath := "output.txt"
+	args := []string{"--template=template.tmpl", "--output=" + outputPath, "test.idl"}
+
+	err := run(args, wrapper)
+	require.NoError(t, err)
+
+	// Verify the output content
+	content, err := wrapper.ReadFile(outputPath)
+	require.NoError(t, err)
+
+	outputStr := string(content)
+	require.Contains(t, outputStr, "File generated by tools/cmd/idlgen.go")
+	require.Contains(t, outputStr, "\n\nMyInterface;GPUDevice;")
+}