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Copy pathPythonParser.cs
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2733 lines (2433 loc) · 91.3 KB
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using System.Collections.ObjectModel;
using DotPython.Language.Ast;
using DotPython.Language.Diagnostics;
using DotPython.Language.Syntax;
using DotPython.Language.Text;
using DotPython.ParserGenerator.Generation;
namespace DotPython.ParserGenerator;
public static class PythonParser
{
public static PythonParseResult Parse(SourceText source)
{
ArgumentNullException.ThrowIfNull(source);
var tokenization = PythonTokenizer.Tokenize(source);
var executableTokens = tokenization
.Tokens.Where(token => token.Kind != SyntaxTokenKind.NonSignificantNewLine)
.ToArray();
var grammarMatch = GeneratedPythonGrammar.Grammar.Match(executableTokens);
var result = new Parser(tokenization).Parse();
if (!result.Success || grammarMatch.Success)
{
return result;
}
var tokenIndex = Math.Min(grammarMatch.FurthestTokenIndex, executableTokens.Length - 1);
var diagnostics = new List<Diagnostic>(result.Diagnostics)
{
new(
"DPY2011",
"The generated Python grammar rejected syntax accepted by the AST builder.",
DiagnosticSeverity.Error,
executableTokens[tokenIndex].Span
),
};
return new PythonParseResult(source, result.Module, diagnostics);
}
private sealed class Parser
{
private readonly List<Diagnostic> _diagnostics;
private readonly SourceText _source;
private readonly SyntaxToken[] _tokens;
private int _functionDepth;
private int _position;
internal Parser(TokenizationResult tokenization)
{
_source = tokenization.Source;
_diagnostics = [.. tokenization.Diagnostics];
_tokens =
[
.. tokenization.Tokens.Where(token =>
token.Kind != SyntaxTokenKind.NonSignificantNewLine
),
];
}
internal PythonParseResult Parse()
{
var statements = ParseStatements(stopAtDedent: false);
var moduleSpan =
statements.Count == 0
? new TextSpan(0, 0)
: TextSpan.FromBounds(statements[0].Span.Start, statements[^1].Span.End);
var module = new PythonModule(statements, moduleSpan);
return new PythonParseResult(_source, module, _diagnostics);
}
private ReadOnlyCollection<PythonStatement> ParseStatements(bool stopAtDedent)
{
var statements = new List<PythonStatement>();
SkipNewLines();
while (
Current.Kind != SyntaxTokenKind.EndOfFile
&& !(stopAtDedent && Current.Kind == SyntaxTokenKind.Dedent)
)
{
var start = _position;
if (Current.Kind == SyntaxTokenKind.Indent)
{
Report("DPY2006", "Unexpected indentation.", Current.Span);
_position++;
}
else if (Current.Kind == SyntaxTokenKind.Dedent)
{
Report("DPY2007", "Unexpected dedent.", Current.Span);
_position++;
}
else if (IsKeyword("if"))
{
statements.Add(ParseIfStatement());
}
else if (IsKeyword("while"))
{
statements.Add(ParseWhileStatement());
}
else if (IsKeyword("for"))
{
statements.Add(ParseForStatement());
}
else if (IsKeyword("with"))
{
statements.Add(ParseWithStatement());
}
else if (IsKeyword("try"))
{
statements.Add(ParseTryStatement());
}
else if (IsKeyword("def"))
{
statements.Add(ParseFunctionDefinition(Array.Empty<PythonExpression>()));
}
else if (IsKeyword("class"))
{
statements.Add(ParseClassDefinition(Array.Empty<PythonExpression>()));
}
else if (Current.Kind == SyntaxTokenKind.At)
{
var decorated = ParseDecoratedDefinition();
if (decorated is not null)
{
statements.Add(decorated);
}
}
else
{
ParseSimpleStatements(statements);
}
if (_position == start)
{
ReportExpected("a statement", Current.Span);
_position++;
}
SkipNewLines();
}
return statements.AsReadOnly();
}
private PythonIfStatement ParseIfStatement()
{
var start = Advance().Span.Start;
var clauses = new List<PythonConditionalClause>();
while (true)
{
var condition = ParseRequiredExpression("a condition after 'if' or 'elif'");
var colon = Expect(SyntaxTokenKind.Colon, "':' after the condition");
var body = ParseSuite();
var clauseEnd = GetBodyEnd(body, colon.Span.End);
clauses.Add(
new PythonConditionalClause(
condition,
body,
TextSpan.FromBounds(condition.Span.Start, clauseEnd)
)
);
if (!MatchKeyword("elif", out _))
{
break;
}
}
IReadOnlyList<PythonStatement> elseBody = Array.Empty<PythonStatement>();
var end = clauses[^1].Span.End;
if (MatchKeyword("else", out _))
{
var colon = Expect(SyntaxTokenKind.Colon, "':' after 'else'");
elseBody = ParseSuite();
end = GetBodyEnd(elseBody, colon.Span.End);
}
return new PythonIfStatement(
clauses.AsReadOnly(),
elseBody,
TextSpan.FromBounds(start, end)
);
}
private PythonWhileStatement ParseWhileStatement()
{
var start = Advance().Span.Start;
var condition = ParseRequiredExpression("a condition after 'while'");
var colon = Expect(SyntaxTokenKind.Colon, "':' after the condition");
var body = ParseSuite();
IReadOnlyList<PythonStatement> elseBody = Array.Empty<PythonStatement>();
var end = GetBodyEnd(body, colon.Span.End);
if (MatchKeyword("else", out _))
{
var elseColon = Expect(SyntaxTokenKind.Colon, "':' after 'else'");
elseBody = ParseSuite();
end = GetBodyEnd(elseBody, elseColon.Span.End);
}
return new PythonWhileStatement(
condition,
body,
elseBody,
TextSpan.FromBounds(start, end)
);
}
private PythonForStatement ParseForStatement()
{
var start = Advance().Span.Start;
var target = ParseForTargets();
if (!MatchKeyword("in", out _))
{
ReportExpected("'in' after the loop target", Current.Span);
}
var iterable = ParseRequiredExpressionList("an iterable after 'in'");
var colon = Expect(SyntaxTokenKind.Colon, "':' after the iterable");
var body = ParseSuite();
IReadOnlyList<PythonStatement> elseBody = Array.Empty<PythonStatement>();
var end = GetBodyEnd(body, colon.Span.End);
if (MatchKeyword("else", out _))
{
var elseColon = Expect(SyntaxTokenKind.Colon, "':' after 'else'");
elseBody = ParseSuite();
end = GetBodyEnd(elseBody, elseColon.Span.End);
}
return new PythonForStatement(
target,
iterable,
body,
elseBody,
TextSpan.FromBounds(start, end)
);
}
private PythonExpression ParseForTargets()
{
var first = ParseForTargetAtom();
if (Current.Kind != SyntaxTokenKind.Comma)
{
return first;
}
var elements = new List<PythonExpression> { first };
while (Match(SyntaxTokenKind.Comma))
{
if (IsKeyword("in") || Current.Kind == SyntaxTokenKind.Colon)
{
break;
}
elements.Add(ParseForTargetAtom());
}
return new PythonTupleExpression(
elements.AsReadOnly(),
TextSpan.FromBounds(elements[0].Span.Start, elements[^1].Span.End)
);
}
private PythonExpression ParseForTargetAtom()
{
if (Match(SyntaxTokenKind.LeftParenthesis, out var leftParenthesis))
{
var inner = ParseForTargets();
var end = ExpectClosingDelimiter(
SyntaxTokenKind.RightParenthesis,
"')'",
inner.Span.End
);
return inner is PythonTupleExpression tuple
? tuple with
{
Span = TextSpan.FromBounds(leftParenthesis.Span.Start, end),
}
: inner;
}
var targetToken = Expect(SyntaxTokenKind.Identifier, "a target after 'for'");
if (targetToken.Text.Length != 0 && IsReservedKeyword(targetToken.Text))
{
Report(
"DPY2010",
$"The keyword '{targetToken.Text}' cannot be used as a loop target.",
targetToken.Span
);
}
return new PythonNameExpression(targetToken.Text, targetToken.Span);
}
private PythonWithStatement ParseWithStatement()
{
var start = Advance().Span.Start;
var items = new List<PythonWithItem>();
while (true)
{
var context = ParseRequiredExpression("a context manager after 'with'");
PythonExpression? target = null;
if (MatchKeyword("as", out _))
{
target = ParseExpression();
if (target is null)
{
ReportExpected("a target after 'as'", Current.Span);
}
else if (!IsAssignableTarget(target))
{
Report("DPY2005", "This expression cannot be assigned to.", target.Span);
target = null;
}
}
items.Add(
new PythonWithItem(
context,
target,
TextSpan.FromBounds(
context.Span.Start,
target?.Span.End ?? context.Span.End
)
)
);
if (!Match(SyntaxTokenKind.Comma))
{
break;
}
}
var colon = Expect(SyntaxTokenKind.Colon, "':' after the context managers");
var body = ParseSuite();
var end = GetBodyEnd(body, colon.Span.End);
return new PythonWithStatement(
items.AsReadOnly(),
body,
TextSpan.FromBounds(start, end)
);
}
private PythonTryStatement ParseTryStatement()
{
var start = Advance().Span.Start;
var colon = Expect(SyntaxTokenKind.Colon, "':' after 'try'");
var body = ParseSuite();
var handlers = new List<PythonExceptHandler>();
var sawBareHandler = false;
var end = GetBodyEnd(body, colon.Span.End);
while (MatchKeyword("except", out var exceptToken))
{
PythonExpression? type = null;
PythonNameExpression? target = null;
if (Current.Kind != SyntaxTokenKind.Colon)
{
type = ParseRequiredExpression("an exception type after 'except'");
if (MatchKeyword("as", out _))
{
var targetToken = Expect(SyntaxTokenKind.Identifier, "a target after 'as'");
if (IsReservedKeyword(targetToken.Text))
{
Report(
"DPY2010",
$"The keyword '{targetToken.Text}' cannot be used as an exception target.",
targetToken.Span
);
}
target = new PythonNameExpression(targetToken.Text, targetToken.Span);
}
}
else
{
if (sawBareHandler)
{
Report(
"DPY2012",
"A try statement cannot contain more than one bare except clause.",
exceptToken.Span
);
}
sawBareHandler = true;
}
var handlerColon = Expect(SyntaxTokenKind.Colon, "':' after the except clause");
var handlerBody = ParseSuite();
end = GetBodyEnd(handlerBody, handlerColon.Span.End);
handlers.Add(
new PythonExceptHandler(
type,
target,
handlerBody,
TextSpan.FromBounds(exceptToken.Span.Start, end)
)
);
if (sawBareHandler && IsKeyword("except"))
{
Report(
"DPY2013",
"A bare except clause must be the last exception handler.",
Current.Span
);
}
}
IReadOnlyList<PythonStatement> elseBody = Array.Empty<PythonStatement>();
if (MatchKeyword("else", out var elseToken))
{
if (handlers.Count == 0)
{
Report(
"DPY2014",
"A try statement requires an except clause before 'else'.",
elseToken.Span
);
}
var elseColon = Expect(SyntaxTokenKind.Colon, "':' after 'else'");
elseBody = ParseSuite();
end = GetBodyEnd(elseBody, elseColon.Span.End);
}
IReadOnlyList<PythonStatement> finallyBody = Array.Empty<PythonStatement>();
if (MatchKeyword("finally", out _))
{
var finallyColon = Expect(SyntaxTokenKind.Colon, "':' after 'finally'");
finallyBody = ParseSuite();
end = GetBodyEnd(finallyBody, finallyColon.Span.End);
}
if (handlers.Count == 0 && finallyBody.Count == 0)
{
Report(
"DPY2015",
"A try statement requires at least one except or finally clause.",
new TextSpan(start, Math.Max(1, end - start))
);
}
return new PythonTryStatement(
body,
handlers.AsReadOnly(),
elseBody,
finallyBody,
TextSpan.FromBounds(start, end)
);
}
private PythonStatement? ParseDecoratedDefinition()
{
var start = Current.Span.Start;
var decorators = new List<PythonExpression>();
while (Current.Kind == SyntaxTokenKind.At)
{
Advance();
var decorator = ParsePrimary();
if (decorator is null)
{
ReportExpected("a decorator expression after '@'", Current.Span);
SynchronizeLine();
}
else
{
decorators.Add(decorator);
if (!Match(SyntaxTokenKind.NewLine))
{
ReportExpected("a new line after the decorator", Current.Span);
SynchronizeLine();
}
}
SkipNewLines();
}
if (IsKeyword("def"))
{
return ParseFunctionDefinition(decorators.AsReadOnly(), start);
}
if (IsKeyword("class"))
{
return ParseClassDefinition(decorators.AsReadOnly(), start);
}
Report(
"DPY2020",
"Expected a function or class definition after the decorators.",
Current.Span
);
return null;
}
private PythonFunctionDefinitionStatement ParseFunctionDefinition(
IReadOnlyList<PythonExpression> decorators,
int? decoratedStart = null
)
{
var start = decoratedStart ?? Current.Span.Start;
Advance();
var nameToken = Expect(SyntaxTokenKind.Identifier, "a function name after 'def'");
if (IsReservedKeyword(nameToken.Text))
{
Report(
"DPY2010",
$"The keyword '{nameToken.Text}' cannot be used as a function name.",
nameToken.Span
);
}
var name = new PythonNameExpression(nameToken.Text, nameToken.Span);
Expect(SyntaxTokenKind.LeftParenthesis, "'(' after the function name");
var parameters = new List<PythonParameter>();
var parameterNames = new HashSet<string>(StringComparer.Ordinal);
var sawDefault = false;
if (Current.Kind != SyntaxTokenKind.RightParenthesis)
{
while (true)
{
var parameter = Expect(SyntaxTokenKind.Identifier, "a parameter name");
PythonExpression? defaultValue = null;
if (Match(SyntaxTokenKind.Equal))
{
defaultValue = ParseExpression();
if (defaultValue is null)
{
ReportExpected("a default value after '='", Current.Span);
}
}
if (!string.IsNullOrEmpty(parameter.Text))
{
if (IsReservedKeyword(parameter.Text))
{
Report(
"DPY2010",
$"The keyword '{parameter.Text}' cannot be used as a parameter.",
parameter.Span
);
}
if (!parameterNames.Add(parameter.Text))
{
Report(
"DPY2009",
$"Duplicate parameter '{parameter.Text}'.",
parameter.Span
);
}
if (defaultValue is not null)
{
sawDefault = true;
}
else if (sawDefault)
{
Report(
"DPY2016",
"A parameter without a default follows a parameter with a default.",
parameter.Span
);
}
parameters.Add(
new PythonParameter(
parameter.Text,
defaultValue,
defaultValue is null
? parameter.Span
: TextSpan.FromBounds(
parameter.Span.Start,
defaultValue.Span.End
)
)
);
}
if (!Match(SyntaxTokenKind.Comma))
{
break;
}
if (Current.Kind == SyntaxTokenKind.RightParenthesis)
{
break;
}
}
}
Expect(SyntaxTokenKind.RightParenthesis, "')' after the parameters");
var colon = Expect(SyntaxTokenKind.Colon, "':' after the function signature");
_functionDepth++;
IReadOnlyList<PythonStatement> body;
try
{
body = ParseSuite();
}
finally
{
_functionDepth--;
}
return new PythonFunctionDefinitionStatement(
decorators,
name,
parameters.AsReadOnly(),
body,
TextSpan.FromBounds(start, GetBodyEnd(body, colon.Span.End))
);
}
private PythonClassDefinitionStatement ParseClassDefinition(
IReadOnlyList<PythonExpression> decorators,
int? decoratedStart = null
)
{
var start = decoratedStart ?? Current.Span.Start;
Advance();
var nameToken = Expect(SyntaxTokenKind.Identifier, "a class name after 'class'");
if (IsReservedKeyword(nameToken.Text))
{
Report(
"DPY2010",
$"The keyword '{nameToken.Text}' cannot be used as a class name.",
nameToken.Span
);
}
var name = new PythonNameExpression(nameToken.Text, nameToken.Span);
var colon = Expect(SyntaxTokenKind.Colon, "':' after the class name");
var enclosingFunctionDepth = _functionDepth;
_functionDepth = 0;
IReadOnlyList<PythonStatement> body;
try
{
body = ParseSuite();
}
finally
{
_functionDepth = enclosingFunctionDepth;
}
return new PythonClassDefinitionStatement(
decorators,
name,
body,
TextSpan.FromBounds(start, GetBodyEnd(body, colon.Span.End))
);
}
private IReadOnlyList<PythonStatement> ParseSuite()
{
if (!Match(SyntaxTokenKind.NewLine))
{
var statements = new List<PythonStatement>();
ParseSimpleStatements(statements);
if (statements.Count == 0)
{
ReportExpected("a simple statement suite", Current.Span);
}
return statements.AsReadOnly();
}
SkipNewLines();
if (!Match(SyntaxTokenKind.Indent))
{
ReportExpected("an indented suite", Current.Span);
return Array.Empty<PythonStatement>();
}
var body = ParseStatements(stopAtDedent: true);
if (!Match(SyntaxTokenKind.Dedent))
{
ReportExpected("the end of the indented suite", Current.Span);
}
if (body.Count == 0)
{
ReportExpected("at least one statement in the suite", Current.Span);
}
return body;
}
private void ParseSimpleStatements(List<PythonStatement> statements)
{
while (
Current.Kind
is not (
SyntaxTokenKind.NewLine
or SyntaxTokenKind.Dedent
or SyntaxTokenKind.EndOfFile
)
)
{
var statement = ParseSimpleStatement();
if (statement is not null)
{
statements.Add(statement);
}
else
{
SynchronizeStatement();
}
if (!Match(SyntaxTokenKind.Semicolon))
{
break;
}
if (
Current.Kind
is SyntaxTokenKind.NewLine
or SyntaxTokenKind.Dedent
or SyntaxTokenKind.EndOfFile
)
{
break;
}
}
if (Current.Kind == SyntaxTokenKind.NewLine)
{
_position++;
}
else if (Current.Kind is not (SyntaxTokenKind.Dedent or SyntaxTokenKind.EndOfFile))
{
Report(
"DPY2003",
"Expected a new line or semicolon after the statement.",
Current.Span
);
SynchronizeLine();
}
}
private PythonStatement? ParseSimpleStatement()
{
if (IsKeyword("return"))
{
return ParseReturnStatement();
}
if (IsKeyword("break"))
{
return new PythonBreakStatement(Advance().Span);
}
if (IsKeyword("continue"))
{
return new PythonContinueStatement(Advance().Span);
}
if (IsKeyword("pass"))
{
return new PythonPassStatement(Advance().Span);
}
if (IsKeyword("assert"))
{
return ParseAssertStatement();
}
if (IsKeyword("del"))
{
return ParseDeleteStatement();
}
if (IsKeyword("global"))
{
return ParseScopeDeclarationStatement(isGlobal: true);
}
if (IsKeyword("nonlocal"))
{
return ParseScopeDeclarationStatement(isGlobal: false);
}
if (IsKeyword("raise"))
{
return ParseRaiseStatement();
}
if (IsKeyword("import"))
{
return ParseImportStatement();
}
if (IsKeyword("from"))
{
return ParseFromImportStatement();
}
if (
Current.Kind == SyntaxTokenKind.Identifier
&& IsUnsupportedStatementKeyword(Current.Text)
)
{
Report(
"DPY2004",
$"The '{Current.Text}' statement is not supported in this position.",
Current.Span
);
return null;
}
var expression = ParseExpression();
if (expression is null)
{
return null;
}
if (Current.Kind == SyntaxTokenKind.Comma)
{
expression = ParseBareTupleTail(expression);
}
if (Match(SyntaxTokenKind.Equal))
{
var value = ParseExpressionListValue();
if (value is null)
{
ReportExpected("an expression after '='", Current.Span);
return null;
}
if (!IsAssignableTarget(expression))
{
Report("DPY2005", "This expression cannot be assigned to.", expression.Span);
return null;
}
return new PythonAssignmentStatement(
expression,
value,
TextSpan.FromBounds(expression.Span.Start, value.Span.End)
);
}
var augmentedOperator = Current.Kind switch
{
SyntaxTokenKind.PlusEqual => PythonBinaryOperator.Add,
SyntaxTokenKind.MinusEqual => PythonBinaryOperator.Subtract,
SyntaxTokenKind.StarEqual => PythonBinaryOperator.Multiply,
SyntaxTokenKind.SlashEqual => PythonBinaryOperator.TrueDivide,
SyntaxTokenKind.DoubleSlashEqual => PythonBinaryOperator.FloorDivide,
SyntaxTokenKind.PercentEqual => PythonBinaryOperator.Modulo,
SyntaxTokenKind.DoubleStarEqual => PythonBinaryOperator.Power,
_ => (PythonBinaryOperator?)null,
};
if (augmentedOperator is not null)
{
Advance();
var value = ParseExpressionListValue();
if (value is null)
{
ReportExpected(
"an expression after the augmented assignment operator",
Current.Span
);
return null;
}
if (
expression
is not (
PythonNameExpression
or PythonSubscriptionExpression
or PythonAttributeExpression
)
)
{
Report("DPY2005", "This expression cannot be assigned to.", expression.Span);
return null;
}
return new PythonAugmentedAssignmentStatement(
expression,
augmentedOperator.Value,
value,
TextSpan.FromBounds(expression.Span.Start, value.Span.End)
);
}
return new PythonExpressionStatement(expression, expression.Span);
}
private PythonImportStatement ParseImportStatement()
{
var start = Advance().Span.Start;
var imports = ParseImportAliases("a module name after 'import'", allowDotted: true);
var end = imports.Count == 0 ? start : imports[^1].Span.End;
return new PythonImportStatement(imports, TextSpan.FromBounds(start, end));
}
private PythonFromImportStatement ParseFromImportStatement()
{
var start = Advance().Span.Start;
var (moduleName, moduleSpan) = ParseRelativeModuleName();
if (!MatchKeyword("import", out _))
{
ReportExpected("'import' after the module name", Current.Span);
}
var parenthesized = Match(SyntaxTokenKind.LeftParenthesis, out _);
var imports = ParseImportAliases(
"a name after 'import'",
allowDotted: false,
allowTrailingComma: parenthesized
);
var end = imports.Count == 0 ? moduleSpan.End : imports[^1].Span.End;
if (parenthesized)
{
end = ExpectClosingDelimiter(SyntaxTokenKind.RightParenthesis, "')'", end);
}
return new PythonFromImportStatement(
moduleName,
imports,
TextSpan.FromBounds(start, end)
);
}
private ReadOnlyCollection<PythonImportAlias> ParseImportAliases(
string expected,
bool allowDotted,
bool allowTrailingComma = false
)
{
var imports = new List<PythonImportAlias>();
while (true)
{
var (name, nameSpan) = allowDotted
? ParseDottedImportName(expected)
: ReadSimpleImportName(expected);
SyntaxToken? alias = null;
if (MatchKeyword("as", out _))
{
alias = ExpectImportName("an alias after 'as'");
}
var end = alias?.Span.End ?? nameSpan.End;
if (name.Length != 0)
{
imports.Add(
new PythonImportAlias(
name,
alias is { Text.Length: > 0 } ? alias.Text : null,
TextSpan.FromBounds(nameSpan.Start, end)
)
);
}
if (!Match(SyntaxTokenKind.Comma))
{
break;
}
if (allowTrailingComma && Current.Kind == SyntaxTokenKind.RightParenthesis)
{
break;
}
}
return imports.AsReadOnly();
}
private (string Name, TextSpan Span) ParseRelativeModuleName()
{
if (Current.Kind is not (SyntaxTokenKind.Dot or SyntaxTokenKind.Ellipsis))
{
return ParseDottedImportName("a module name after 'from'");
}
var start = Current.Span.Start;
var dotCount = 0;
var end = start;
while (Current.Kind is SyntaxTokenKind.Dot or SyntaxTokenKind.Ellipsis)
{
var token = Advance();
dotCount += token.Kind == SyntaxTokenKind.Ellipsis ? 3 : 1;
end = token.Span.End;
}
var suffix = string.Empty;
if (Current.Kind == SyntaxTokenKind.Identifier && !IsKeyword("import"))
{
(suffix, var suffixSpan) = ParseDottedImportName("a module name after the dots");
end = suffixSpan.End;
}
return (new string('.', dotCount) + suffix, TextSpan.FromBounds(start, end));