Merge pull request #88 from alexnask/new_pos_context

Reworked position context to use tokenizer, works in more contexts

.github/workflows/main.yml

@@ -28,7 +28,11 @@ jobs:
         FILE=zig-cache/bin/zls
 
         if test -f "$FILE"; then
-          exit 0
+          if zig build test; then
+            exit 0
+          else
+            exit 1
+          fi
         else
           exit 1
         fi

build.zig

@@ -131,7 +131,15 @@ pub fn build(b: *std.build.Builder) !void {
     const run_step = b.step("run", "Run the app");
     run_step.dependOn(&run_cmd.step);
 
-    // const configure_step = std.build.Step.init("config", b.allocator, config);
     const configure_step = b.step("config", "Configure zls");
     configure_step.makeFn = config;
+
+    const test_step = b.step("test", "Run all the tests");
+    test_step.dependOn(&exe.step);
+
+    var unit_tests = b.addTest("tests/unit_tests.zig");
+    unit_tests.addPackage(.{  .name = "analysis", .path = "src/analysis.zig" });
+    unit_tests.addPackage(.{  .name = "types", .path = "src/types.zig" });
+    unit_tests.setBuildMode(.Debug);
+    test_step.dependOn(&unit_tests.step);
 }

src/analysis.zig

@@ -284,6 +284,92 @@ fn resolveReturnType(analysis_ctx: *AnalysisContext, fn_decl: *ast.Node.FnProto)
     };
 }
 
+/// Resolves the child type of an optional type
+fn resolveUnwrapOptionalType(analysis_ctx: *AnalysisContext, opt: *ast.Node) ?*ast.Node {
+    if (opt.cast(ast.Node.PrefixOp)) |prefix_op| {
+        if (prefix_op.op == .OptionalType) {
+            return resolveTypeOfNode(analysis_ctx, prefix_op.rhs);
+        }
+    }
+
+    return null;
+}
+
+/// Resolves the child type of a defer type
+fn resolveDerefType(analysis_ctx: *AnalysisContext, deref: *ast.Node) ?*ast.Node {
+    if (deref.cast(ast.Node.PrefixOp)) |pop| {
+        if (pop.op == .PtrType) {
+            const op_token_id = analysis_ctx.tree().token_ids[pop.op_token];
+            switch (op_token_id) {
+                .Asterisk => return resolveTypeOfNode(analysis_ctx, pop.rhs),
+                .LBracket, .AsteriskAsterisk => return null,
+                else => unreachable,
+            }
+        }
+    }
+    return null;
+}
+
+fn makeSliceType(analysis_ctx: *AnalysisContext, child_type: *ast.Node) ?*ast.Node {
+    // TODO: Better values for fields, better way to do this?
+    var slice_type = analysis_ctx.arena.allocator.create(ast.Node.PrefixOp) catch return null;
+    slice_type.* = .{
+        .op_token = child_type.firstToken(),
+        .op = .{
+            .SliceType = .{
+                .allowzero_token = null,
+                .align_info = null,
+                .const_token = null,
+                .volatile_token = null,
+                .sentinel = null,
+            },
+        },
+        .rhs = child_type,
+    };
+
+    return &slice_type.base;
+}
+
+/// Resolves bracket access type (both slicing and array access)
+fn resolveBracketAccessType(
+    analysis_ctx: *AnalysisContext,
+    lhs: *ast.Node,
+    rhs: enum { Single, Range },
+) ?*ast.Node {
+    if (lhs.cast(ast.Node.PrefixOp)) |pop| {
+        switch (pop.op) {
+            .SliceType => {
+                if (rhs == .Single) return resolveTypeOfNode(analysis_ctx, pop.rhs);
+                return lhs;
+            },
+            .ArrayType => {
+                if (rhs == .Single) return resolveTypeOfNode(analysis_ctx, pop.rhs);
+                return makeSliceType(analysis_ctx, pop.rhs);
+            },
+            .PtrType => {
+                if (pop.rhs.cast(std.zig.ast.Node.PrefixOp)) |child_pop| {
+                    switch (child_pop.op) {
+                        .ArrayType => {
+                            if (rhs == .Single) {
+                                return resolveTypeOfNode(analysis_ctx, child_pop.rhs);
+                            }
+                            return lhs;
+                        },
+                        else => {},
+                    }
+                }
+            },
+            else => {},
+        }
+    }
+    return null;
+}
+
+/// Called to remove one level of pointerness before a field access
+fn resolveFieldAccessLhsType(analysis_ctx: *AnalysisContext, lhs: *ast.Node) *ast.Node {
+    return resolveDerefType(analysis_ctx, lhs) orelse lhs;
+}
+
 /// Resolves the type of a node
 pub fn resolveTypeOfNode(analysis_ctx: *AnalysisContext, node: *ast.Node) ?*ast.Node {
     switch (node.id) {
@@ -318,6 +404,28 @@ pub fn resolveTypeOfNode(analysis_ctx: *AnalysisContext, node: *ast.Node) ?*ast.
                 else => decl,
             };
         },
+        .SuffixOp => {
+            const suffix_op = node.cast(ast.Node.SuffixOp).?;
+            switch (suffix_op.op) {
+                .UnwrapOptional => {
+                    const left_type = resolveTypeOfNode(analysis_ctx, suffix_op.lhs) orelse return null;
+                    return resolveUnwrapOptionalType(analysis_ctx, left_type);
+                },
+                .Deref => {
+                    const left_type = resolveTypeOfNode(analysis_ctx, suffix_op.lhs) orelse return null;
+                    return resolveDerefType(analysis_ctx, left_type);
+                },
+                .ArrayAccess => {
+                    const left_type = resolveTypeOfNode(analysis_ctx, suffix_op.lhs) orelse return null;
+                    return resolveBracketAccessType(analysis_ctx, left_type, .Single);
+                },
+                .Slice => {
+                    const left_type = resolveTypeOfNode(analysis_ctx, suffix_op.lhs) orelse return null;
+                    return resolveBracketAccessType(analysis_ctx, left_type, .Range);
+                },
+                else => {},
+            }
+        },
         .InfixOp => {
             const infix_op = node.cast(ast.Node.InfixOp).?;
             switch (infix_op.op) {
@@ -327,25 +435,31 @@ pub fn resolveTypeOfNode(analysis_ctx: *AnalysisContext, node: *ast.Node) ?*ast.
                     var rhs_str = nodeToString(analysis_ctx.tree(), infix_op.rhs) orelse return null;
                     // Use the analysis context temporary arena to store the rhs string.
                     rhs_str = std.mem.dupe(&analysis_ctx.arena.allocator, u8, rhs_str) catch return null;
-                    const left = resolveTypeOfNode(analysis_ctx, infix_op.lhs) orelse return null;
+
-                    const child = getChild(analysis_ctx.tree(), left, rhs_str) orelse return null;
+                    // If we are accessing a pointer type, remove one pointerness level :)
+                    const left_type = resolveFieldAccessLhsType(
+                        analysis_ctx,
+                        resolveTypeOfNode(analysis_ctx, infix_op.lhs) orelse return null,
+                    );
+
+                    const child = getChild(analysis_ctx.tree(), left_type, rhs_str) orelse return null;
                     return resolveTypeOfNode(analysis_ctx, child);
                 },
+                .UnwrapOptional => {
+                    const left_type = resolveTypeOfNode(analysis_ctx, infix_op.lhs) orelse return null;
+                    return resolveUnwrapOptionalType(analysis_ctx, left_type);
+                },
                 else => {},
             }
         },
         .PrefixOp => {
             const prefix_op = node.cast(ast.Node.PrefixOp).?;
             switch (prefix_op.op) {
-                .SliceType, .ArrayType => return node,
+                .SliceType,
-                .PtrType => {
+                .ArrayType,
-                    const op_token_id = analysis_ctx.tree().token_ids[prefix_op.op_token];
+                .OptionalType,
-                    switch (op_token_id) {
+                .PtrType,
-                        .Asterisk => return resolveTypeOfNode(analysis_ctx, prefix_op.rhs),
+                => return node,
-                        .LBracket, .AsteriskAsterisk => return null,
-                        else => unreachable,
-                    }
-                },
                 .Try => {
                     const rhs_type = resolveTypeOfNode(analysis_ctx, prefix_op.rhs) orelse return null;
                     switch (rhs_type.id) {
@@ -433,37 +547,50 @@ pub fn collectImports(import_arr: *std.ArrayList([]const u8), tree: *ast.Tree) !
 pub fn getFieldAccessTypeNode(
     analysis_ctx: *AnalysisContext,
     tokenizer: *std.zig.Tokenizer,
-    line_length: usize,
 ) ?*ast.Node {
     var current_node = analysis_ctx.in_container;
-    var current_container = analysis_ctx.in_container;
 
     while (true) {
-        var next = tokenizer.next();
+        const tok = tokenizer.next();
-        switch (next.id) {
+        switch (tok.id) {
-            .Eof => return current_node,
+            .Eof => return resolveFieldAccessLhsType(analysis_ctx, current_node),
             .Identifier => {
-                if (getChildOfSlice(analysis_ctx.tree(), analysis_ctx.scope_nodes, tokenizer.buffer[next.loc.start..next.loc.end])) |child| {
+                if (getChildOfSlice(analysis_ctx.tree(), analysis_ctx.scope_nodes, tokenizer.buffer[tok.loc.start..tok.loc.end])) |child| {
-                    if (resolveTypeOfNode(analysis_ctx, child)) |node_type| {
+                    if (resolveTypeOfNode(analysis_ctx, child)) |child_type| {
-                        current_node = node_type;
+                        current_node = child_type;
                     } else return null;
                 } else return null;
             },
             .Period => {
-                var after_period = tokenizer.next();
+                const after_period = tokenizer.next();
-                if (after_period.id == .Eof or after_period.id == .Comma) {
+                switch (after_period.id) {
-                    return current_node;
+                    .Eof => return resolveFieldAccessLhsType(analysis_ctx, current_node),
-                } else if (after_period.id == .Identifier) {
+                    .Identifier => {
-                    // TODO: This works for now, maybe we should filter based on the partial identifier ourselves?
+                        if (after_period.loc.end == tokenizer.buffer.len) return resolveFieldAccessLhsType(analysis_ctx, current_node);
-                    if (after_period.loc.end == line_length) return current_node;
 
-                    if (getChild(analysis_ctx.tree(), current_node, tokenizer.buffer[after_period.loc.start..after_period.loc.end])) |child| {
+                        current_node = resolveFieldAccessLhsType(analysis_ctx, current_node);
-                        if (resolveTypeOfNode(analysis_ctx, child)) |child_type| {
+                        if (getChild(analysis_ctx.tree(), current_node, tokenizer.buffer[after_period.loc.start..after_period.loc.end])) |child| {
+                            if (resolveTypeOfNode(analysis_ctx, child)) |child_type| {
+                                current_node = child_type;
+                            } else return null;
+                        } else return null;
+                    },
+                    .QuestionMark => {
+                        if (resolveUnwrapOptionalType(analysis_ctx, current_node)) |child_type| {
                             current_node = child_type;
                         } else return null;
-                    } else return null;
+                    },
+                    else => {
+                        std.debug.warn("Unrecognized token {} after period.\n", .{after_period.id});
+                        return null;
+                    },
                 }
             },
+            .PeriodAsterisk => {
+                if (resolveDerefType(analysis_ctx, current_node)) |child_type| {
+                    current_node = child_type;
+                } else return null;
+            },
             .LParen => {
                 switch (current_node.id) {
                     .FnProto => {
@@ -472,7 +599,7 @@ pub fn getFieldAccessTypeNode(
                             current_node = ret;
                             // Skip to the right paren
                             var paren_count: usize = 1;
-                            next = tokenizer.next();
+                            var next = tokenizer.next();
                             while (next.id != .Eof) : (next = tokenizer.next()) {
                                 if (next.id == .RParen) {
                                     paren_count -= 1;
@@ -481,30 +608,46 @@ pub fn getFieldAccessTypeNode(
                                     paren_count += 1;
                                 }
                             } else return null;
-                        } else {
+                        } else return null;
-                            return null;
-                        }
                     },
                     else => {},
                 }
             },
-            .Keyword_const, .Keyword_var => {
+            .LBracket => {
-                next = tokenizer.next();
+                var brack_count: usize = 1;
-                if (next.id == .Identifier) {
+                var next = tokenizer.next();
-                    next = tokenizer.next();
+                var is_range = false;
-                    if (next.id != .Equal) return null;
+                while (next.id != .Eof) : (next = tokenizer.next()) {
-                    continue;
+                    if (next.id == .RBracket) {
-                }
+                        brack_count -= 1;
+                        if (brack_count == 0) break;
+                    } else if (next.id == .LBracket) {
+                        brack_count += 1;
+                    } else if (next.id == .Ellipsis2 and brack_count == 1) {
+                        is_range = true;
+                    }
+                } else return null;
+
+                if (resolveBracketAccessType(
+                    analysis_ctx,
+                    current_node,
+                    if (is_range) .Range else .Single,
+                )) |child_type| {
+                    current_node = child_type;
+                } else return null;
+            },
+            else => {
+                std.debug.warn("Unimplemented token: {}\n", .{tok.id});
+                return null;
             },
-            else => std.debug.warn("Not implemented; {}\n", .{next.id}),
         }
 
-        if (current_node.id == .ContainerDecl or current_node.id == .Root) {
+        if (current_node.cast(ast.Node.ContainerDecl)) |container_decl| {
-            current_container = current_node;
+            analysis_ctx.onContainer(container_decl) catch return null;
         }
     }
 
-    return current_node;
+    return resolveFieldAccessLhsType(analysis_ctx, current_node);
 }
 
 pub fn isNodePublic(tree: *ast.Tree, node: *ast.Node) bool {
@@ -763,3 +906,137 @@ pub fn getImportStr(tree: *ast.Tree, source_index: usize) ?[]const u8 {
     }
     return null;
 }
+
+const types = @import("types.zig");
+pub const SourceRange = std.zig.Token.Loc;
+
+pub const PositionContext = union(enum) {
+    builtin: SourceRange,
+    comment,
+    string_literal: SourceRange,
+    field_access: SourceRange,
+    var_access: SourceRange,
+    enum_literal,
+    other,
+    empty,
+
+    pub fn range(self: PositionContext) ?SourceRange {
+        return switch (self) {
+            .builtin => |r| r,
+            .comment => null,
+            .string_literal => |r| r,
+            .field_access => |r| r,
+            .var_access => |r| r,
+            .enum_literal => null,
+            .other => null,
+            .empty => null,
+        };
+    }
+};
+
+const StackState = struct {
+    ctx: PositionContext,
+    stack_id: enum { Paren, Bracket, Global },
+};
+
+fn peek(arr: *std.ArrayList(StackState)) !*StackState {
+    if (arr.items.len == 0) {
+        try arr.append(.{ .ctx = .empty, .stack_id = .Global });
+    }
+    return &arr.items[arr.items.len - 1];
+}
+
+fn tokenRangeAppend(prev: SourceRange, token: std.zig.Token) SourceRange {
+    return .{
+        .start = prev.start,
+        .end = token.loc.end,
+    };
+}
+
+pub fn documentPositionContext(allocator: *std.mem.Allocator, document: types.TextDocument, position: types.Position) !PositionContext {
+    const line = try document.getLine(@intCast(usize, position.line));
+    const pos_char = @intCast(usize, position.character) + 1;
+    const idx = if (pos_char > line.len) line.len else pos_char;
+
+    var arena = std.heap.ArenaAllocator.init(allocator);
+    defer arena.deinit();
+
+    var tokenizer = std.zig.Tokenizer.init(line[0..idx]);
+    var stack = try std.ArrayList(StackState).initCapacity(&arena.allocator, 8);
+
+    while (true) {
+        const tok = tokenizer.next();
+        // Early exits.
+        switch (tok.id) {
+            .Invalid, .Invalid_ampersands => {
+                // Single '@' do not return a builtin token so we check this on our own.
+                if (line[idx - 1] == '@') {
+                    return PositionContext{
+                        .builtin = .{
+                            .start = idx - 1,
+                            .end = idx,
+                        },
+                    };
+                }
+                return .other;
+            },
+            .LineComment, .DocComment, .ContainerDocComment => return .comment,
+            .Eof => break,
+            else => {},
+        }
+
+        // State changes
+        var curr_ctx = try peek(&stack);
+        switch (tok.id) {
+            .StringLiteral, .MultilineStringLiteralLine => curr_ctx.ctx = .{ .string_literal = tok.loc },
+            .Identifier => switch (curr_ctx.ctx) {
+                .empty => curr_ctx.ctx = .{ .var_access = tok.loc },
+                else => {},
+            },
+            .Builtin => switch (curr_ctx.ctx) {
+                .empty => curr_ctx.ctx = .{ .builtin = tok.loc },
+                else => {},
+            },
+            .Period, .PeriodAsterisk => switch (curr_ctx.ctx) {
+                .empty => curr_ctx.ctx = .enum_literal,
+                .enum_literal => curr_ctx.ctx = .empty,
+                .field_access => {},
+                .other => {},
+                else => curr_ctx.ctx = .{
+                    .field_access = tokenRangeAppend(curr_ctx.ctx.range().?, tok),
+                },
+            },
+            .QuestionMark => switch (curr_ctx.ctx) {
+                .field_access => {},
+                else => curr_ctx.ctx = .empty,
+            },
+            .LParen => try stack.append(.{ .ctx = .empty, .stack_id = .Paren }),
+            .LBracket => try stack.append(.{ .ctx = .empty, .stack_id = .Bracket }),
+            .RParen => {
+                _ = stack.pop();
+                if (curr_ctx.stack_id != .Paren) {
+                    (try peek(&stack)).ctx = .empty;
+                }
+            },
+            .RBracket => {
+                _ = stack.pop();
+                if (curr_ctx.stack_id != .Bracket) {
+                    (try peek(&stack)).ctx = .empty;
+                }
+            },
+            else => curr_ctx.ctx = .empty,
+        }
+
+        switch (curr_ctx.ctx) {
+            .field_access => |r| curr_ctx.ctx = .{
+                .field_access = tokenRangeAppend(r, tok),
+            },
+            else => {},
+        }
+    }
+
+    return block: {
+        if (stack.popOrNull()) |state| break :block state.ctx;
+        break :block .empty;
+    };
+}

src/main.zig

@@ -273,6 +273,20 @@ fn nodeToCompletion(
             });
         },
         .PrefixOp => {
+            const prefix_op = node.cast(std.zig.ast.Node.PrefixOp).?;
+            switch (prefix_op.op) {
+                .ArrayType, .SliceType => {},
+                .PtrType => {
+                    if (prefix_op.rhs.cast(std.zig.ast.Node.PrefixOp)) |child_pop| {
+                        switch (child_pop.op) {
+                            .ArrayType => {},
+                            else => return,
+                        }
+                    } else return;
+                },
+                else => return,
+            }
+
             try list.append(.{
                 .label = "len",
                 .kind = .Field,
@@ -389,7 +403,7 @@ fn hoverDefinitionGlobal(id: i64, pos_index: usize, handle: *DocumentStore.Handl
 fn getSymbolFieldAccess(
     analysis_ctx: *DocumentStore.AnalysisContext,
     position: types.Position,
-    line_start_idx: usize,
+    range: analysis.SourceRange,
     config: Config,
 ) !?*std.zig.ast.Node {
     const pos_index = try analysis_ctx.handle.document.positionToIndex(position);
@@ -397,12 +411,10 @@ fn getSymbolFieldAccess(
     if (name.len == 0) return null;
 
     const line = try analysis_ctx.handle.document.getLine(@intCast(usize, position.line));
-    var tokenizer = std.zig.Tokenizer.init(line[line_start_idx..]);
+    var tokenizer = std.zig.Tokenizer.init(line[range.start..range.end]);
 
-    const line_length = @ptrToInt(name.ptr) - @ptrToInt(line.ptr) + name.len - line_start_idx;
     name = try std.mem.dupe(&analysis_ctx.arena.allocator, u8, name);
-
+    if (analysis.getFieldAccessTypeNode(analysis_ctx, &tokenizer)) |container| {
-    if (analysis.getFieldAccessTypeNode(analysis_ctx, &tokenizer, line_length)) |container| {
         return analysis.getChild(analysis_ctx.tree(), container, name);
     }
     return null;
@@ -412,14 +424,14 @@ fn gotoDefinitionFieldAccess(
     id: i64,
     handle: *DocumentStore.Handle,
     position: types.Position,
-    line_start_idx: usize,
+    range: analysis.SourceRange,
     config: Config,
 ) !void {
     var arena = std.heap.ArenaAllocator.init(allocator);
     defer arena.deinit();
 
     var analysis_ctx = try document_store.analysisContext(handle, &arena, try handle.document.positionToIndex(position), config.zig_lib_path);
-    const decl = (try getSymbolFieldAccess(&analysis_ctx, position, line_start_idx, config)) orelse return try respondGeneric(id, null_result_response);
+    const decl = (try getSymbolFieldAccess(&analysis_ctx, position, range, config)) orelse return try respondGeneric(id, null_result_response);
     return try gotoDefinitionSymbol(id, &analysis_ctx, decl);
 }
 
@@ -427,14 +439,14 @@ fn hoverDefinitionFieldAccess(
     id: i64,
     handle: *DocumentStore.Handle,
     position: types.Position,
-    line_start_idx: usize,
+    range: analysis.SourceRange,
     config: Config,
 ) !void {
     var arena = std.heap.ArenaAllocator.init(allocator);
     defer arena.deinit();
 
     var analysis_ctx = try document_store.analysisContext(handle, &arena, try handle.document.positionToIndex(position), config.zig_lib_path);
-    const decl = (try getSymbolFieldAccess(&analysis_ctx, position, line_start_idx, config)) orelse return try respondGeneric(id, null_result_response);
+    const decl = (try getSymbolFieldAccess(&analysis_ctx, position, range, config)) orelse return try respondGeneric(id, null_result_response);
     return try hoverSymbol(id, &analysis_ctx, decl);
 }
 
@@ -490,7 +502,7 @@ fn completeGlobal(id: i64, pos_index: usize, handle: *DocumentStore.Handle, conf
     });
 }
 
-fn completeFieldAccess(id: i64, handle: *DocumentStore.Handle, position: types.Position, line_start_idx: usize, config: Config) !void {
+fn completeFieldAccess(id: i64, handle: *DocumentStore.Handle, position: types.Position, range: analysis.SourceRange, config: Config) !void {
     var arena = std.heap.ArenaAllocator.init(allocator);
     defer arena.deinit();
 
@@ -498,10 +510,9 @@ fn completeFieldAccess(id: i64, handle: *DocumentStore.Handle, position: types.P
     var completions = std.ArrayList(types.CompletionItem).init(&arena.allocator);
 
     const line = try handle.document.getLine(@intCast(usize, position.line));
-    var tokenizer = std.zig.Tokenizer.init(line[line_start_idx..]);
+    var tokenizer = std.zig.Tokenizer.init(line[range.start..range.end]);
-    const line_length = line.len - line_start_idx;
 
-    if (analysis.getFieldAccessTypeNode(&analysis_ctx, &tokenizer, line_length)) |node| {
+    if (analysis.getFieldAccessTypeNode(&analysis_ctx, &tokenizer)) |node| {
         try nodeToCompletion(&completions, &analysis_ctx, handle, node, config);
     }
     try send(types.Response{
@@ -550,136 +561,6 @@ const builtin_completions = block: {
     };
 };
 
-const PositionContext = union(enum) {
-    builtin,
-    comment,
-    string_literal,
-    field_access: usize,
-    var_access,
-    other,
-    empty,
-};
-
-const token_separators = [_]u8{
-    ' ', '\t', '(', ')', '[', ']',
-    '{', '}',  '|', '=', '!', ';',
-    ',', '?',  ':', '%', '+', '*',
-    '>', '<',  '~', '-', '/', '&',
-};
-
-fn documentPositionContext(doc: types.TextDocument, pos_index: usize) PositionContext {
-    // First extract the whole current line up to the cursor.
-    var curr_position = pos_index;
-    while (curr_position > 0) : (curr_position -= 1) {
-        if (doc.text[curr_position - 1] == '\n') break;
-    }
-
-    var line = doc.text[curr_position .. pos_index + 1];
-    // Strip any leading whitespace.
-    var skipped_ws: usize = 0;
-    while (skipped_ws < line.len and (line[skipped_ws] == ' ' or line[skipped_ws] == '\t')) : (skipped_ws += 1) {}
-    if (skipped_ws >= line.len) return .empty;
-    line = line[skipped_ws..];
-
-    // Quick exit for comment lines and multi line string literals.
-    if (line.len >= 2 and line[0] == '/' and line[1] == '/')
-        return .comment;
-    if (line.len >= 2 and line[0] == '\\' and line[1] == '\\')
-        return .string_literal;
-
-    // TODO: This does not detect if we are in a string literal over multiple lines.
-    // Find out what context we are in.
-    // Go over the current line character by character
-    // and determine the context.
-    curr_position = 0;
-    var expr_start: usize = skipped_ws;
-
-    // std.debug.warn("{}", .{curr_position});
-
-    if (pos_index != 0 and doc.text[pos_index - 1] == ')')
-        return .{ .field_access = expr_start };
-
-    var new_token = true;
-    var context: PositionContext = .other;
-    var string_pop_ctx: PositionContext = .other;
-    while (curr_position < line.len) : (curr_position += 1) {
-        const c = line[curr_position];
-        const next_char = if (curr_position < line.len - 1) line[curr_position + 1] else null;
-
-        if (context != .string_literal and c == '"') {
-            expr_start = curr_position + skipped_ws;
-            context = .string_literal;
-            continue;
-        }
-
-        if (context == .string_literal) {
-            // Skip over escaped quotes
-            if (c == '\\' and next_char != null and next_char.? == '"') {
-                curr_position += 1;
-            } else if (c == '"') {
-                context = string_pop_ctx;
-                string_pop_ctx = .other;
-                new_token = true;
-            }
-
-            continue;
-        }
-
-        if (c == '/' and next_char != null and next_char.? == '/') {
-            context = .comment;
-            break;
-        }
-
-        if (std.mem.indexOfScalar(u8, &token_separators, c) != null) {
-            expr_start = curr_position + skipped_ws + 1;
-            new_token = true;
-            context = .other;
-            continue;
-        }
-
-        if (c == '.' and (!new_token or context == .string_literal)) {
-            new_token = true;
-            if (next_char != null and next_char.? == '.') continue;
-            context = .{ .field_access = expr_start };
-            continue;
-        }
-
-        if (new_token) {
-            const access_ctx: PositionContext = if (context == .field_access)
-                .{ .field_access = expr_start }
-            else
-                .var_access;
-
-            new_token = false;
-
-            if (c == '_' or std.ascii.isAlpha(c)) {
-                context = access_ctx;
-            } else if (c == '@') {
-                // This checks for @"..." identifiers by controlling
-                // the context the string will set after it is over.
-                if (next_char != null and next_char.? == '"') {
-                    string_pop_ctx = access_ctx;
-                }
-                context = .builtin;
-            } else {
-                context = .other;
-            }
-            continue;
-        }
-
-        if (context == .field_access or context == .var_access or context == .builtin) {
-            if (c != '_' and !std.ascii.isAlNum(c)) {
-                context = .other;
-            }
-            continue;
-        }
-
-        context = .other;
-    }
-
-    return context;
-}
-
 fn loadConfig(folder_path: []const u8) ?Config {
     var folder = std.fs.cwd().openDir(folder_path, .{}) catch return null;
     defer folder.close();
@@ -851,7 +732,7 @@ fn processJsonRpc(parser: *std.json.Parser, json: []const u8, config: Config) !v
         };
         if (pos.character >= 0) {
             const pos_index = try handle.document.positionToIndex(pos);
-            const pos_context = documentPositionContext(handle.document, pos_index);
+            const pos_context = try analysis.documentPositionContext(allocator, handle.document, pos);
 
             const this_config = configFromUriOr(uri, config);
             switch (pos_context) {
@@ -865,7 +746,7 @@ fn processJsonRpc(parser: *std.json.Parser, json: []const u8, config: Config) !v
                     },
                 }),
                 .var_access, .empty => try completeGlobal(id, pos_index, handle, this_config),
-                .field_access => |start_idx| try completeFieldAccess(id, handle, pos, start_idx, this_config),
+                .field_access => |range| try completeFieldAccess(id, handle, pos, range, this_config),
                 else => try respondGeneric(id, no_completions_response),
             }
         } else {
@@ -894,7 +775,7 @@ fn processJsonRpc(parser: *std.json.Parser, json: []const u8, config: Config) !v
         };
         if (pos.character >= 0) {
             const pos_index = try handle.document.positionToIndex(pos);
-            const pos_context = documentPositionContext(handle.document, pos_index);
+            const pos_context = try analysis.documentPositionContext(allocator, handle.document, pos);
 
             switch (pos_context) {
                 .var_access => try gotoDefinitionGlobal(
@@ -903,16 +784,18 @@ fn processJsonRpc(parser: *std.json.Parser, json: []const u8, config: Config) !v
                     handle,
                     configFromUriOr(uri, config),
                 ),
-                .field_access => |start_idx| try gotoDefinitionFieldAccess(
+                .field_access => |range| try gotoDefinitionFieldAccess(
                     id,
                     handle,
                     pos,
-                    start_idx,
+                    range,
                     configFromUriOr(uri, config),
                 ),
                 .string_literal => try gotoDefinitionString(id, pos_index, handle, config),
                 else => try respondGeneric(id, null_result_response),
             }
+        } else {
+            try respondGeneric(id, null_result_response);
         }
     } else if (std.mem.eql(u8, method, "textDocument/hover")) {
         const document = params.getValue("textDocument").?.Object;
@@ -930,7 +813,7 @@ fn processJsonRpc(parser: *std.json.Parser, json: []const u8, config: Config) !v
         };
         if (pos.character >= 0) {
             const pos_index = try handle.document.positionToIndex(pos);
-            const pos_context = documentPositionContext(handle.document, pos_index);
+            const pos_context = try analysis.documentPositionContext(allocator, handle.document, pos);
 
             switch (pos_context) {
                 .var_access => try hoverDefinitionGlobal(
@@ -939,15 +822,17 @@ fn processJsonRpc(parser: *std.json.Parser, json: []const u8, config: Config) !v
                     handle,
                     configFromUriOr(uri, config),
                 ),
-                .field_access => |start_idx| try hoverDefinitionFieldAccess(
+                .field_access => |range| try hoverDefinitionFieldAccess(
                     id,
                     handle,
                     pos,
-                    start_idx,
+                    range,
                     configFromUriOr(uri, config),
                 ),
                 else => try respondGeneric(id, null_result_response),
             }
+        } else {
+            try respondGeneric(id, null_result_response);
         }
     } else if (root.Object.getValue("id")) |_| {
         std.debug.warn("Method with return value not implemented: {}", .{method});

tests/unit_tests.zig

@@ -0,0 +1,102 @@
+const analysis = @import("analysis");
+const types = @import("types");
+
+const std = @import("std");
+
+const allocator = std.testing.allocator;
+
+fn makeDocument(uri: []const u8, text: []const u8) !types.TextDocument {
+    const mem = try allocator.alloc(u8, text.len);
+    std.mem.copy(u8, mem, text);
+
+    return types.TextDocument{
+        .uri = uri,
+        .mem = mem,
+        .text = mem[0..],
+    };
+}
+
+fn freeDocument(doc: types.TextDocument) void {
+    allocator.free(doc.text);
+}
+
+fn makeUnnamedDocument(text: []const u8) !types.TextDocument {
+    return try makeDocument("test", text);
+}
+
+fn testContext(comptime line: []const u8, comptime tag: var, comptime range: ?[]const u8) !void {
+    const cursor_idx = comptime std.mem.indexOf(u8, line, "<cursor>").?;
+    const final_line = line[0..cursor_idx] ++ line[cursor_idx + "<cursor>".len ..];
+
+    const doc = try makeUnnamedDocument(final_line);
+    defer freeDocument(doc);
+
+    const ctx = try analysis.documentPositionContext(allocator, doc, types.Position{
+        .line = 0,
+        .character = @intCast(i64, cursor_idx - 1),
+    });
+
+    if (std.meta.activeTag(ctx) != tag) {
+        std.debug.warn("Expected tag {}, got {}\n", .{ tag, std.meta.activeTag(ctx) });
+        return error.DifferentTag;
+    }
+
+    if (ctx.range()) |ctx_range| {
+        if (range == null) {
+            std.debug.warn("Expected null range, got `{}`\n", .{
+                doc.text[ctx_range.start..ctx_range.end],
+            });
+        } else {
+            const range_start = comptime std.mem.indexOf(u8, final_line, range.?).?;
+            const range_end = range_start + range.?.len;
+
+            if (range_start != ctx_range.start or range_end != ctx_range.end) {
+                std.debug.warn("Expected range `{}` ({}..{}), got `{}` ({}..{})\n", .{
+                    doc.text[range_start..range_end],         range_start,     range_end,
+                    doc.text[ctx_range.start..ctx_range.end], ctx_range.start, ctx_range.end,
+                });
+                return error.DifferentRange;
+            }
+        }
+    } else if (range != null) {
+        std.debug.warn("Unexpected null range\n", .{});
+        return error.DifferentRange;
+    }
+}
+
+test "documentPositionContext" {
+    try testContext(
+        \\const this_var = id<cursor>entifier;
+    ,
+        .var_access,
+        "id",
+    );
+
+    try testContext(
+        \\if (displ.*.?.c.*[0].<cursor>@"a" == foo) {
+    ,
+        .field_access,
+        "displ.*.?.c.*[0].",
+    );
+
+    try testContext(
+        \\const arr = std.ArrayList(SomeStruct(a, b, c, d)).in<cursor>it(allocator);
+    ,
+        .field_access,
+        "std.ArrayList(SomeStruct(a, b, c, d)).in",
+    );
+
+    try testContext(
+        \\try erroringFn(the_first[arg], second[a..<cursor>]);
+    ,
+        .empty,
+        null,
+    );
+
+    try testContext(
+        \\    fn add(lhf: lself, rhs: rself) !Se<cursor> {
+    ,
+        .var_access,
+        "Se",
+    );
+}