Add style/method-declaration-format and style/type-parameter-format lint rules

tools/pony-lint/glob_match.pony

@@ -18,8 +18,12 @@ primitive GlobMatch
     _matches(pattern, 0, pattern.size(), text, 0, text.size())
 
   fun _matches(
-    p: String val, ps: USize, pe: USize,
-    t: String val, ts: USize, te: USize)
+    p: String val,
+    ps: USize,
+    pe: USize,
+    t: String val,
+    ts: USize,
+    te: USize)
     : Bool
   =>
     """
@@ -100,8 +104,12 @@ primitive GlobMatch
     _match_segment(p, ps, pe, t, ts, te)
 
   fun _match_leading_star(
-    p: String val, ps: USize, pe: USize,
-    t: String val, ts: USize, te: USize)
+    p: String val,
+    ps: USize,
+    pe: USize,
+    t: String val,
+    ts: USize,
+    te: USize)
     : Bool
   =>
     """
@@ -119,8 +127,12 @@ primitive GlobMatch
     false
 
   fun _match_segment(
-    p: String val, ps: USize, pe: USize,
-    t: String val, ts: USize, te: USize)
+    p: String val,
+    ps: USize,
+    pe: USize,
+    t: String val,
+    ts: USize,
+    te: USize)
     : Bool
   =>
     """

tools/pony-lint/main.pony

@@ -93,6 +93,8 @@ actor Main
         .> push(ControlStructureAlignment)
         .> push(TypeAliasFormat)
         .> push(ArrayLiteralFormat)
+        .> push(MethodDeclarationFormat)
+        .> push(TypeParameterFormat)
     end
 
     // Handle --explain

tools/pony-lint/method_declaration_format.pony

@@ -0,0 +1,223 @@
+use ast = "pony_compiler"
+
+primitive MethodDeclarationFormat is ASTRule
+  """
+  Checks formatting of multiline method declarations per the style guide.
+
+  When a method's parameters span multiple lines, checks:
+  - Each parameter is on its own line (no two parameters sharing a line).
+
+  When a method declaration spans multiple lines, checks:
+  - The return type ':' is at the method keyword's column + 2 (one indent
+    level deeper) when it appears as the first non-whitespace on its line.
+  - The '=>' is at the method keyword's column when it appears as the first
+    non-whitespace on its line.
+
+  Single-line method declarations are not checked.
+  """
+  fun id(): String val => "style/method-declaration-format"
+  fun category(): String val => "style"
+
+  fun description(): String val =>
+    "multiline method declaration formatting"
+      + " (parameter layout, return type and '=>' alignment)"
+
+  fun default_status(): RuleStatus => RuleOn
+
+  fun node_filter(): Array[ast.TokenId] val =>
+    [ ast.TokenIds.tk_fun()
+      ast.TokenIds.tk_new()
+      ast.TokenIds.tk_be() ]
+
+  fun check(node: ast.AST box, source: SourceFile val)
+    : Array[Diagnostic val] val
+  =>
+    """
+    Check formatting of a multiline method declaration.
+    """
+    let keyword_line = node.line()
+    let keyword_col = node.pos()
+
+    // Determine the keyword name for diagnostic messages
+    let keyword_name = _keyword_name(node.id())
+
+    let diags = recover iso Array[Diagnostic val] end
+
+    // Check params (child 3)
+    try
+      let params = node(3)?
+      if params.id() != ast.TokenIds.tk_none() then
+        let num_params = params.num_children()
+        if num_params > 1 then
+          // Find line of first and last param to determine if multiline
+          try
+            let first_param = params(0)?
+            let first_line = _param_line(first_param)
+            let last_line = _last_param_line(params)
+            if first_line != last_line then
+              // Multiline params: check each is on its own line
+              var prev_line = first_line
+              var i: USize = 1
+              while i < num_params do
+                let param_node = params(i)?
+                let param_l = _param_line(param_node)
+                if param_l == prev_line then
+                  diags.push(Diagnostic(id(),
+                    "each parameter should be on its own line"
+                      + " in a multiline declaration",
+                    source.rel_path, param_l, param_node.pos()))
+                end
+                prev_line = param_l
+                i = i + 1
+              end
+            end
+          end
+        end
+      end
+    end
+
+    // Check return type ':' alignment (child 4)
+    try
+      let ret_type = node(4)?
+      if ret_type.id() != ast.TokenIds.tk_none() then
+        let ret_line = ret_type.line()
+        if ret_line > keyword_line then
+          try
+            let line_text = source.lines(ret_line - 1)?
+            (let first_ch, let first_col) = _first_nonws_char(line_text)
+            if first_ch == ':' then
+              let expected_col = keyword_col + 2
+              let actual_col = first_col + 1 // convert 0-based to 1-based
+              if actual_col != expected_col then
+                diags.push(Diagnostic(id(),
+                  "':' should align at column "
+                    + expected_col.string()
+                    + " (indented from '" + keyword_name + "')",
+                  source.rel_path, ret_line, actual_col))
+              end
+            end
+          end
+        end
+      end
+    end
+
+    // Check '=>' alignment (child 6 = body)
+    try
+      let body = node(6)?
+      if body.id() != ast.TokenIds.tk_none() then
+        let body_line = body.line()
+        if body_line > keyword_line then
+          // Scan backward from the line before the body to find '=>'
+          var scan_line = body_line - 1
+          while scan_line > keyword_line do
+            try
+              let line_text = source.lines(scan_line - 1)?
+              (let word, let word_col) =
+                _first_nonws_word(line_text)
+              if word == "=>" then
+                let actual_col = word_col
+                if actual_col != keyword_col then
+                  diags.push(Diagnostic(id(),
+                    "'=>' should align with '" + keyword_name
+                      + "' keyword (column "
+                      + keyword_col.string() + ")",
+                    source.rel_path, scan_line, actual_col))
+                end
+                break
+              end
+              // Stop scanning if we hit a non-blank line that isn't '=>'
+              if word.size() > 0 then break end
+            end
+            scan_line = scan_line - 1
+          end
+        end
+      end
+    end
+
+    consume diags
+
+  fun _keyword_name(token_id: ast.TokenId): String val =>
+    """
+    Return the source keyword for the given method token type.
+    """
+    if token_id == ast.TokenIds.tk_fun() then "fun"
+    elseif token_id == ast.TokenIds.tk_new() then "new"
+    elseif token_id == ast.TokenIds.tk_be() then "be"
+    else "unknown"
+    end
+
+  fun _param_line(param: ast.AST box): USize =>
+    """
+    Get the line number of a parameter node. Since TK_PARAM is abstract
+    (no source position), use the first child's line (the parameter name
+    or dontcare).
+    """
+    try param(0)?.line()
+    else param.line()
+    end
+
+  fun _last_param_line(params: ast.AST box): USize =>
+    """
+    Find the maximum line number across all parameter children.
+    """
+    var max_line: USize = 0
+    var i: USize = 0
+    let count = params.num_children()
+    while i < count do
+      try
+        let p = params(i)?
+        let l = _param_line(p)
+        if l > max_line then max_line = l end
+      end
+      i = i + 1
+    end
+    max_line
+
+  fun _first_nonws_char(line: String val): (U8, USize) =>
+    """
+    Find the first non-whitespace character on a line.
+    Returns `(char, 0-based-index)` or `(0, 0)` if blank.
+    """
+    var i: USize = 0
+    while i < line.size() do
+      try
+        let ch = line(i)?
+        if (ch != ' ') and (ch != '\t') then
+          return (ch, i)
+        end
+      end
+      i = i + 1
+    end
+    (0, 0)
+
+  fun _first_nonws_word(line: String val): (String val, USize) =>
+    """
+    Extract the first non-whitespace word from a line, returning the word
+    and its 1-based column position. Returns `("", 0)` for blank lines.
+    """
+    var i: USize = 0
+    while i < line.size() do
+      try
+        let ch = line(i)?
+        if (ch != ' ') and (ch != '\t') then break end
+      end
+      i = i + 1
+    end
+
+    if i >= line.size() then
+      return ("", 0)
+    end
+
+    let col = i + 1 // 1-based
+    let start = i
+
+    while i < line.size() do
+      try
+        let ch = line(i)?
+        if (ch == ' ') or (ch == '\t') then break end
+      end
+      i = i + 1
+    end
+
+    (recover val line.substring(ISize.from[USize](start),
+      ISize.from[USize](i)) end, col)

tools/pony-lint/test/_ast_test_helper.pony

@@ -16,7 +16,9 @@ primitive \nodoc\ _ASTTestHelper
   directory, not an installed location, so executable-relative discovery
   is not used here.
   """
-  fun compile(h: TestHelper, source: String val,
+  fun compile(
+    h: TestHelper,
+    source: String val,
     filename: String val = "test.pony")
     : (ast.Program val, lint.SourceFile val) ?
   =>