Debugging utilities (#860)

* add debug printing for Ast and DocumentScope

* add optional failing allocator

build.zig

@@ -50,6 +50,18 @@ pub fn build(b: *std.build.Builder) !void {
         b.option(bool, "enable_tracy_callstack", "Enable callstack graphs.") orelse false,
     );
     
+    exe_options.addOption(
+        bool,
+        "enable_failing_allocator",
+        b.option(bool, "enable_failing_allocator", "Whether to use a randomly failing allocator.") orelse false,
+    );
+
+    exe_options.addOption(
+        u32,
+        "enable_failing_allocator_likelihood",
+        b.option(u32, "enable_failing_allocator_likelihood", "The chance that an allocation will fail is `1/likelihood`") orelse 256,
+    );
+
     const version = v: {
         const version_string = b.fmt("{d}.{d}.{d}", .{ zls_version.major, zls_version.minor, zls_version.patch });
 

src/analysis.zig

@@ -2389,30 +2389,6 @@ pub const DocumentScope = struct {
     error_completions: CompletionSet,
     enum_completions: CompletionSet,
 
-    pub fn debugPrint(self: DocumentScope) void {
-        for (self.scopes.items) |scope| {
-            log.debug(
-                \\--------------------------
-                \\Scope {}, loc: [{d}, {d})
-                \\ {d} usingnamespaces
-                \\Decls:
-            , .{
-                scope.data,
-                scope.loc.start,
-                scope.loc.end,
-                scope.uses.len,
-            });
-
-            var decl_it = scope.decls.iterator();
-            var idx: usize = 0;
-            while (decl_it.next()) |_| : (idx += 1) {
-                if (idx != 0) log.debug(", ", .{});
-            }
-            // log.debug("{s}", .{name_decl.key});
-            log.debug("\n--------------------------\n", .{});
-        }
-    }
-
     pub fn deinit(self: *DocumentScope, allocator: std.mem.Allocator) void {
         for (self.scopes.items) |*scope| {
             scope.deinit(allocator);

src/debug.zig

@@ -0,0 +1,136 @@
+const std = @import("std");
+
+const analysis = @import("analysis.zig");
+const offsets = @import("offsets.zig");
+
+pub fn printTree(tree: std.zig.Ast) void {
+    if (!std.debug.runtime_safety) @compileError("this function should only be used in debug mode!");
+
+    std.debug.print(
+        \\
+        \\nodes   tag                  lhs rhs token
+        \\-----------------------------------------------
+        \\
+    , .{});
+    var i: usize = 0;
+    while (i < tree.nodes.len) : (i += 1) {
+        std.debug.print("    {d:<3} {s:<20} {d:<3} {d:<3} {d:<3} {s}\n", .{
+            i,
+            @tagName(tree.nodes.items(.tag)[i]),
+            tree.nodes.items(.data)[i].lhs,
+            tree.nodes.items(.data)[i].rhs,
+            tree.nodes.items(.main_token)[i],
+            offsets.tokenToSlice(tree, tree.nodes.items(.main_token)[i]),
+        });
+    }
+
+    std.debug.print(
+        \\
+        \\tokens  tag                  start
+        \\----------------------------------
+        \\
+    , .{});
+    i = 0;
+    while (i < tree.tokens.len) : (i += 1) {
+        std.debug.print("    {d:<3} {s:<20} {d:<}\n", .{
+            i,
+            @tagName(tree.tokens.items(.tag)[i]),
+            tree.tokens.items(.start)[i],
+        });
+    }
+}
+
+pub fn printDocumentScope(doc_scope: analysis.DocumentScope) void {
+    if (!std.debug.runtime_safety) @compileError("this function should only be used in debug mode!");
+
+    for (doc_scope.scopes.items) |scope, i| {
+        if (i != 0) std.debug.print("\n\n", .{});
+        std.debug.print(
+            \\[{d}, {d}] {}
+            \\usingnamespaces: {d}
+            \\Decls:
+            \\
+        , .{
+            scope.loc.start,
+            scope.loc.end,
+            scope.data,
+            scope.uses.items.len,
+        });
+
+        var decl_it = scope.decls.iterator();
+        var idx: usize = 0;
+        while (decl_it.next()) |entry| : (idx += 1) {
+            std.debug.print("    {s:<8} {}\n", .{ entry.key_ptr.*, entry.value_ptr.* });
+        }
+    }
+}
+
+pub const FailingAllocator = struct {
+    internal_allocator: std.mem.Allocator,
+    random: std.rand.DefaultPrng,
+    likelihood: u32,
+
+    /// the chance that an allocation will fail is `1/likelihood`
+    /// `likelihood == 0` means that every allocation will fail
+    /// `likelihood == std.math.intMax(u32)` means that no allocation will be forced to fail
+    pub fn init(internal_allocator: std.mem.Allocator, likelihood: u32) FailingAllocator {
+        var seed = std.mem.zeroes([8]u8);
+        std.os.getrandom(&seed) catch {};
+
+        return FailingAllocator{
+            .internal_allocator = internal_allocator,
+            .random = std.rand.DefaultPrng.init(@bitCast(u64, seed)),
+            .likelihood = likelihood,
+        };
+    }
+
+    pub fn allocator(self: *FailingAllocator) std.mem.Allocator {
+        return .{
+            .ptr = self,
+            .vtable = &.{
+                .alloc = alloc,
+                .resize = resize,
+                .free = free,
+            },
+        };
+    }
+
+    fn alloc(
+        ctx: *anyopaque,
+        len: usize,
+        log2_ptr_align: u8,
+        return_address: usize,
+    ) ?[*]u8 {
+        const self = @ptrCast(*FailingAllocator, @alignCast(@alignOf(FailingAllocator), ctx));
+        if (shouldFail(self)) return null;
+        return self.internal_allocator.rawAlloc(len, log2_ptr_align, return_address);
+    }
+
+    fn resize(
+        ctx: *anyopaque,
+        old_mem: []u8,
+        log2_old_align: u8,
+        new_len: usize,
+        ra: usize,
+    ) bool {
+        const self = @ptrCast(*FailingAllocator, @alignCast(@alignOf(FailingAllocator), ctx));
+        if (!self.internal_allocator.rawResize(old_mem, log2_old_align, new_len, ra))
+            return false;
+        return true;
+    }
+
+    fn free(
+        ctx: *anyopaque,
+        old_mem: []u8,
+        log2_old_align: u8,
+        ra: usize,
+    ) void {
+        const self = @ptrCast(*FailingAllocator, @alignCast(@alignOf(FailingAllocator), ctx));
+        self.internal_allocator.rawFree(old_mem, log2_old_align, ra);
+    }
+
+    fn shouldFail(self: *FailingAllocator) bool {
+        if (self.likelihood == std.math.maxInt(u32)) return false;
+        return 0 == self.random.random().intRangeAtMostBiased(u32, 0, self.likelihood);
+    }
+};

src/main.zig

@@ -8,6 +8,7 @@ const configuration = @import("configuration.zig");
 const Server = @import("Server.zig");
 const setup = @import("setup.zig");
 const Header = @import("Header.zig");
+const debug = @import("debug.zig");
 
 const logger = std.log.scoped(.main);
 
@@ -263,9 +264,12 @@ const stack_frames = switch (zig_builtin.mode) {
 pub fn main() !void {
     var gpa_state = std.heap.GeneralPurposeAllocator(.{ .stack_trace_frames = stack_frames }){};
     defer _ = gpa_state.deinit();
-    var tracy_state = if (tracy.enable_allocation) tracy.tracyAllocator(gpa_state.allocator()) else void{};
 
-    const allocator: std.mem.Allocator = if (tracy.enable_allocation) tracy_state.allocator() else gpa_state.allocator();
+    var tracy_state = if (tracy.enable_allocation) tracy.tracyAllocator(gpa_state.allocator()) else void{};
+    const inner_allocator: std.mem.Allocator = if (tracy.enable_allocation) tracy_state.allocator() else gpa_state.allocator();
+    
+    var failing_allocator_state = if(build_options.enable_failing_allocator) debug.FailingAllocator.init(inner_allocator, build_options.enable_failing_allocator_likelihood) else void{};
+    const allocator: std.mem.Allocator = if(build_options.enable_failing_allocator) failing_allocator_state.allocator() else inner_allocator;
 
     var config = ConfigWithPath{
         .config = undefined,

src/zls.zig

@@ -3,6 +3,7 @@
 
 pub const analysis = @import("analysis.zig");
 pub const Header = @import("Header.zig");
+pub const debug = @import("debug.zig");
 pub const offsets = @import("offsets.zig");
 pub const Config = @import("Config.zig");
 pub const Server = @import("Server.zig");