feat: more fmt improvements (#224)

This adds support for optional newline before curly brace in the rule declaration.

```
// This is the default
rule a {
```
vs

```
rule a
{
```

It also adds support for empty lines before and after section headers. Each one is a separate option - you can have them before section headers but not after, vice versa, both, or none.

```
rule a {

  meta:

    foo = "bar"
```

vs

```
// This is the default (no empty lines)
rule a {
  meta:
    foo = "bar"
```

This also fixes an issue where we were not inserting newlines before meta definitions, so if you had two meta definitions on the same line the formatter left them like that. They are now fixed so that each meta definition goes on a separate line.

cli/src/commands/fmt.rs

@@ -45,7 +45,14 @@ pub fn exec_fmt(
         .align_patterns(config.patterns.align_values)
         .indent_section_headers(config.rule.indent_section_headers)
         .indent_section_contents(config.rule.indent_section_contents)
-        .indent_spaces(config.rule.indent_spaces);
+        .indent_spaces(config.rule.indent_spaces)
+        .newline_before_curly_brace(config.rule.newline_before_curly_brace)
+        .empty_line_before_section_header(
+            config.rule.empty_line_before_section_header,
+        )
+        .empty_line_after_section_header(
+            config.rule.empty_line_after_section_header,
+        );
     let mut changed = false;
 
     for file in files {

cli/src/config.rs

@@ -33,6 +33,12 @@ pub struct Rule {
     pub indent_section_contents: bool,
     /// Number of spaces for indent. Set to 0 to use tabs.
     pub indent_spaces: u8,
+    /// Insert a newline after the rule declaration but before the curly brace.
+    pub newline_before_curly_brace: bool,
+    /// Insert an empty line before section headers.
+    pub empty_line_before_section_header: bool,
+    /// Insert an empty line after section headers.
+    pub empty_line_after_section_header: bool,
 }
 
 /// Meta specific formatting information.
@@ -57,6 +63,9 @@ impl Default for Config {
                     indent_section_headers: true,
                     indent_section_contents: true,
                     indent_spaces: 2,
+                    newline_before_curly_brace: false,
+                    empty_line_before_section_header: true,
+                    empty_line_after_section_header: false,
                 },
                 meta: Meta { align_values: true },
                 patterns: Patterns { align_values: true },

docs/YARA-X Config Guide.md

@@ -9,6 +9,9 @@ The `yr` command looks in `${HOME}/.yara-x.toml` when starting up. If that file
 does not exist the default values are used.
 
 An example `.yara-x.toml` file is below, with comments that explain each option.
+The values for each option are the default values that are used if omit the
+option.
+
 This is the definitive list of supported configuration options, and will be
 updated as more are added.
 
@@ -60,6 +63,64 @@ rule.indent_section_contents = true
 # rule.indent_section_headers and rule.indent_section_contents
 rule.indent_spaces = 2
 
+# Add a newline before the curly brace that starts the rule body.
+#
+# rule a {
+#   condition:
+#     true
+# }
+#
+# Becomes:
+#
+# rule a
+# {
+#   condition:
+#     true
+# }
+#
+# Note: If you have multiple newlines before the curly brace and this is set to
+# `true` then this will ensure exactly two newlines are left.
+rule.newline_before_curly_brace = false
+
+# Add an empty line before section headers so that:
+#
+# rule a {
+#   meta:
+#     date = "20240705"
+#   strings:
+#     $ = "AXSERS"
+# }
+#
+# Becomes:
+#
+# rule a {
+#   meta:
+#     date = "20240705"
+#
+#   strings:
+#     $ = "AXSERS"
+# }
+#
+# Note: This does not apply to the first section header defined. All empty lines
+# before the first section header are always removed.
+rule.empty_line_before_section_header = true
+
+# Add an empty line after section headers so that:
+#
+# rule a {
+#   strings:
+#     $ = "AXSERS"
+# }
+#
+# Becomes:
+#
+# rule a {
+#   strings:
+#
+#     $ = "AXSERS"
+# }
+rule.empty_line_after_section_header = false
+
 # Align metadata values so that:
 #
 # rule a {