GN: Make file/dir resolving return errors.

tools/gn/source_dir.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "tools/gn/source_dir.h"
 
 #include "base/logging.h"
 #include "tools/gn/filesystem_utils.h"
 #include "tools/gn/source_file.h"
 
 namespace {
 
 void AssertValueSourceDirString(const std::string& s) {
   if (!s.empty()) {
 #if defined(OS_WIN)
     DCHECK(s[0] == '/' ||
            (s.size() > 2 && s[0] != '/' && s[1] == ':' && IsSlash(s[2])));
 #else
     DCHECK(s[0] == '/');
 #endif
-    DCHECK(EndsWithSlash(s));
+    DCHECK(EndsWithSlash(s)) << s;
   }
 }
 
 }  // namespace
 
 SourceDir::SourceDir() {
 }
 
 SourceDir::SourceDir(const base::StringPiece& p)
     : value_(p.data(), p.size()) {
   if (!EndsWithSlash(value_))
     value_.push_back('/');
   AssertValueSourceDirString(value_);
 }
 
 SourceDir::SourceDir(SwapIn, std::string* s) {
   value_.swap(*s);
   if (!EndsWithSlash(value_))
     value_.push_back('/');
   AssertValueSourceDirString(value_);
 }
 
 SourceDir::~SourceDir() {
 }
 
 SourceFile SourceDir::ResolveRelativeFile(
-    const base::StringPiece& p,
+    const Value& p,
+    Err* err,
     const base::StringPiece& source_root) const {
   SourceFile ret;
-
-  DCHECK(source_root.empty() || !source_root.ends_with("/"));
+  if (!p.VerifyTypeIs(Value::STRING, err))
+    return ret;
 
   // It's an error to resolve an empty string or one that is a directory
   // (indicated by a trailing slash) because this is the function that expects
   // to return a file.
-  if (p.empty() || (p.size() > 0 && p[p.size() - 1] == '/'))
-    return SourceFile();
-  if (p.size() >= 2 && p[0] == '/' && p[1] == '/') {
+  const std::string& str = p.string_value();
+  if (str.empty()) {
+    *err = Err(p, "Empty file path.",
+               "You can't use empty strings as file paths. That's just wrong.");
+    return ret;
+  } else if (str[str.size() - 1] == '/') {
+    *err = Err(p, "File path ends in a slash.",
+               "You specified the path\n  " + str + "\n"
+               "and it ends in a slash, indicating you think it's a directory."
+               "\nBut here you're supposed to be listing a file.");
+    return ret;
+  }
+
+  if (str.size() >= 2 && str[0] == '/' && str[1] == '/') {
     // Source-relative.
-    ret.value_.assign(p.data(), p.size());
+    ret.value_.assign(str.data(), str.size());
     NormalizePath(&ret.value_);
     return ret;
-  } else if (IsPathAbsolute(p)) {
+  } else if (IsPathAbsolute(str)) {
     if (source_root.empty() ||
-        !MakeAbsolutePathRelativeIfPossible(source_root, p, &ret.value_)) {
+        !MakeAbsolutePathRelativeIfPossible(source_root, str, &ret.value_)) {
 #if defined(OS_WIN)
       // On Windows we'll accept "C:\foo" as an absolute path, which we want
       // to convert to "/C:..." here.
-      if (p[0] != '/')
+      if (str[0] != '/')
         ret.value_ = "/";
 #endif
-      ret.value_.append(p.data(), p.size());
+      ret.value_.append(str.data(), str.size());
     }
     NormalizePath(&ret.value_);
     return ret;
   }
 
   if (!source_root.empty()) {
     std::string absolute =
         FilePathToUTF8(Resolve(UTF8ToFilePath(source_root)).AppendASCII(
-            p.as_string()).value());
+            str).value());
     NormalizePath(&absolute);
     if (!MakeAbsolutePathRelativeIfPossible(source_root, absolute,
                                             &ret.value_)) {
 #if defined(OS_WIN)
       // On Windows we'll accept "C:\foo" as an absolute path, which we want
       // to convert to "/C:..." here.
       if (absolute[0] != '/')
         ret.value_ = "/";
 #endif
       ret.value_.append(absolute.data(), absolute.size());
     }
     return ret;
   }
 
   // With no source_root_, there's nothing we can do about
   // e.g. p=../../../path/to/file and value_=//source and we'll
   // errornously return //file.
-  ret.value_.reserve(value_.size() + p.size());
+  ret.value_.reserve(value_.size() + str.size());
   ret.value_.assign(value_);
-  ret.value_.append(p.data(), p.size());
+  ret.value_.append(str.data(), str.size());
 
   NormalizePath(&ret.value_);
   return ret;
 }
 
 SourceDir SourceDir::ResolveRelativeDir(
-    const base::StringPiece& p,
+    const Value& p,
+    Err* err,
+    const base::StringPiece& source_root) const {
+  if (!p.VerifyTypeIs(Value::STRING, err))
+    return SourceDir();
+  return ResolveRelativeDir(p, p.string_value(), err, source_root);
+}
+
+SourceDir SourceDir::ResolveRelativeDir(
+    const Value& blame_but_dont_use,
+    const base::StringPiece& str,
+    Err* err,
     const base::StringPiece& source_root) const {
   SourceDir ret;
 
-  DCHECK(source_root.empty() || !source_root.ends_with("/"));
+  if (str.empty()) {
+    *err = Err(blame_but_dont_use, "Empty directory path.",
+               "You can't use empty strings as directoriers. "

[scottmg, 2015/06/03 21:01:59]

"directories"

+               "That's just wrong.");
+    return ret;
+  }
 
-  if (p.empty())
-    return ret;
-  if (p.size() >= 2 && p[0] == '/' && p[1] == '/') {
+  if (str.size() >= 2 && str[0] == '/' && str[1] == '/') {
     // Source-relative.
-    ret.value_.assign(p.data(), p.size());
+    ret.value_.assign(str.data(), str.size());
     if (!EndsWithSlash(ret.value_))
       ret.value_.push_back('/');
     NormalizePath(&ret.value_);
     return ret;
-  } else if (IsPathAbsolute(p)) {
+  } else if (IsPathAbsolute(str)) {
     if (source_root.empty() ||
-        !MakeAbsolutePathRelativeIfPossible(source_root, p, &ret.value_)) {
+        !MakeAbsolutePathRelativeIfPossible(source_root, str, &ret.value_)) {
 #if defined(OS_WIN)
-      if (p[0] != '/')  // See the file case for why we do this check.
+      if (str[0] != '/')  // See the file case for why we do this check.
         ret.value_ = "/";
 #endif
-      ret.value_.append(p.data(), p.size());
+      ret.value_.append(str.data(), str.size());
     }
     NormalizePath(&ret.value_);
     if (!EndsWithSlash(ret.value_))
       ret.value_.push_back('/');
     return ret;
   }
 
   if (!source_root.empty()) {
     std::string absolute =
         FilePathToUTF8(Resolve(UTF8ToFilePath(source_root)).AppendASCII(
-            p.as_string()).value());
+            str.as_string()).value());
     NormalizePath(&absolute);
     if (!MakeAbsolutePathRelativeIfPossible(source_root, absolute,
                                             &ret.value_)) {
 #if defined(OS_WIN)
       if (absolute[0] != '/')  // See the file case for why we do this check.
         ret.value_ = "/";
 #endif
       ret.value_.append(absolute.data(), absolute.size());
     }
     if (!EndsWithSlash(ret.value_))
       ret.value_.push_back('/');
     return ret;
   }
 
-  ret.value_.reserve(value_.size() + p.size());
+  ret.value_.reserve(value_.size() + str.size());
   ret.value_.assign(value_);
-  ret.value_.append(p.data(), p.size());
+  ret.value_.append(str.data(), str.size());
 
   NormalizePath(&ret.value_);
   if (!EndsWithSlash(ret.value_))
     ret.value_.push_back('/');
   AssertValueSourceDirString(ret.value_);
 
   return ret;
 }
 
 base::FilePath SourceDir::Resolve(const base::FilePath& source_root) const {
@@ skipping 14 matching lines @@
   // String the double-leading slash for source-relative paths.
   converted.assign(&value_[2], value_.size() - 2);
   return source_root.Append(UTF8ToFilePath(converted))
       .NormalizePathSeparatorsTo('/');
 }
 
 void SourceDir::SwapValue(std::string* v) {
   value_.swap(*v);
   AssertValueSourceDirString(value_);
 }