Add --version for outputting version, framework for more actions

src/cli_action.zig

@@ -0,0 +1,107 @@
+const std = @import("std");
+const builtin = @import("builtin");
+const Allocator = std.mem.Allocator;
+const build_config = @import("build_config.zig");
+
+/// Special commands that can be invoked via CLI flags. These are all
+/// invoked by using `+<action>` as a CLI flag. The only exception is
+/// "version" which can be invoked additionally with `--version`.
+pub const Action = enum {
+    /// Output the version and exit
+    version,
+
+    pub const Error = error{
+        /// Multiple actions were detected. You can specify at most one
+        /// action on the CLI otherwise the behavior desired is ambiguous.
+        MultipleActions,
+
+        /// An unknown action was specified.
+        InvalidAction,
+    };
+
+    /// Detect the action from CLI args.
+    pub fn detectCLI(alloc: Allocator) !?Action {
+        var iter = try std.process.argsWithAllocator(alloc);
+        defer iter.deinit();
+        return try detectIter(&iter);
+    }
+
+    /// Detect the action from any iterator, used primarily for tests.
+    pub fn detectIter(iter: anytype) Error!?Action {
+        var pending: ?Action = null;
+        while (iter.next()) |arg| {
+            // Special case, --version always outputs the version no
+            // matter what, no matter what other args exist.
+            if (std.mem.eql(u8, arg, "--version")) return .version;
+
+            // Commands must start with "+"
+            if (arg.len == 0 or arg[0] != '+') continue;
+            if (pending != null) return Error.MultipleActions;
+            pending = std.meta.stringToEnum(Action, arg[1..]) orelse return Error.InvalidAction;
+        }
+
+        return null;
+    }
+
+    /// Run the action. This returns the exit code to exit with.
+    pub fn run(self: Action, alloc: Allocator) !u8 {
+        _ = alloc;
+        return switch (self) {
+            .version => try runVersion(),
+        };
+    }
+};
+
+fn runVersion() !u8 {
+    const stdout = std.io.getStdOut().writer();
+    try stdout.print("Ghostty {s}\n", .{build_config.version_string});
+    return 0;
+}
+
+test "parse action none" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    var iter = try std.process.ArgIteratorGeneral(.{}).init(
+        alloc,
+        "--a=42 --b --b-f=false",
+    );
+    defer iter.deinit();
+    const action = try Action.detectIter(&iter);
+    try testing.expect(action == null);
+}
+
+test "parse action version" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    {
+        var iter = try std.process.ArgIteratorGeneral(.{}).init(
+            alloc,
+            "--a=42 --b --b-f=false --version",
+        );
+        defer iter.deinit();
+        const action = try Action.detectIter(&iter);
+        try testing.expect(action.? == .version);
+    }
+
+    {
+        var iter = try std.process.ArgIteratorGeneral(.{}).init(
+            alloc,
+            "--version --a=42 --b --b-f=false",
+        );
+        defer iter.deinit();
+        const action = try Action.detectIter(&iter);
+        try testing.expect(action.? == .version);
+    }
+
+    {
+        var iter = try std.process.ArgIteratorGeneral(.{}).init(
+            alloc,
+            "--c=84 --d --version --a=42 --b --b-f=false",
+        );
+        defer iter.deinit();
+        const action = try Action.detectIter(&iter);
+        try testing.expect(action.? == .version);
+    }
+}

src/main.zig

@@ -1,10 +1,12 @@
 const std = @import("std");
 const builtin = @import("builtin");
+const Allocator = std.mem.Allocator;
 const build_config = @import("build_config.zig");
 const options = @import("build_options");
 const glfw = @import("glfw");
 const macos = @import("macos");
 const tracy = @import("tracy");
+const cli_action = @import("cli_action.zig");
 const internal_os = @import("os/main.zig");
 const xev = @import("xev");
 const fontconfig = @import("fontconfig");
@@ -32,6 +34,38 @@ pub fn main() !void {
     defer state.deinit();
     const alloc = state.alloc;
 
+    // Before we do anything else, we need to check for special commands
+    // via the CLI flags.
+    if (cli_action.Action.detectCLI(alloc)) |action_| {
+        if (action_) |action| {
+            std.log.info("executing CLI action={}", .{action});
+            std.os.exit(action.run(alloc) catch |err| err: {
+                std.log.err("CLI action failed error={}", .{err});
+                break :err 1;
+            });
+            return;
+        }
+    } else |err| {
+        const stderr = std.io.getStdErr().writer();
+        defer std.os.exit(1);
+        const ErrSet = @TypeOf(err) || error{Unknown};
+        switch (@as(ErrSet, @errSetCast(err))) {
+            error.MultipleActions => try stderr.print(
+                "Error: multiple CLI actions specified. You must specify only one\n" ++
+                    "action starting with the `+` character.\n",
+                .{},
+            ),
+
+            error.InvalidAction => try stderr.print(
+                "Error: unknown CLI action specified. CLI actions are specified with\n" ++
+                    "the '+' character.\n",
+                .{},
+            ),
+
+            else => try stderr.print("invalid CLI invocation err={}\n", .{err}),
+        }
+    }
+
     // Create our app state
     var app = try App.create(alloc);
     defer app.destroy();
@@ -187,6 +221,7 @@ test {
     _ = @import("renderer.zig");
     _ = @import("termio.zig");
     _ = @import("input.zig");
+    _ = @import("cli_action.zig");
 
     // Libraries
     _ = @import("segmented_pool.zig");