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PhabricatorDifferenceEngine.php
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Mon, Dec 2, 08:12

PhabricatorDifferenceEngine.php
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<?php
/**
* Utility class which encapsulates some shared behavior between different
* applications which render diffs.
*
* @task config Configuring the Engine
* @task diff Generating Diffs
*/
final class PhabricatorDifferenceEngine extends Phobject {
private $ignoreWhitespace;
private $oldName;
private $newName;
/* -( Configuring the Engine )--------------------------------------------- */
/**
* If true, ignore whitespace when computing differences.
*
* @param bool Ignore whitespace?
* @return this
* @task config
*/
public function setIgnoreWhitespace($ignore_whitespace) {
$this->ignoreWhitespace = $ignore_whitespace;
return $this;
}
/**
* Set the name to identify the old file with. Primarily cosmetic.
*
* @param string Old file name.
* @return this
* @task config
*/
public function setOldName($old_name) {
$this->oldName = $old_name;
return $this;
}
/**
* Set the name to identify the new file with. Primarily cosmetic.
*
* @param string New file name.
* @return this
* @task config
*/
public function setNewName($new_name) {
$this->newName = $new_name;
return $this;
}
/* -( Generating Diffs )--------------------------------------------------- */
/**
* Generate a raw diff from two raw files. This is a lower-level API than
* @{method:generateChangesetFromFileContent}, but may be useful if you need
* to use a custom parser configuration, as with Diffusion.
*
* @param string Entire previous file content.
* @param string Entire current file content.
* @return string Raw diff between the two files.
* @task diff
*/
public function generateRawDiffFromFileContent($old, $new) {
$options = array();
if ($this->ignoreWhitespace) {
$options[] = '-bw';
}
// Generate diffs with full context.
$options[] = '-U65535';
$old_name = nonempty($this->oldName, '/dev/universe').' 9999-99-99';
$new_name = nonempty($this->newName, '/dev/universe').' 9999-99-99';
$options[] = '-L';
$options[] = $old_name;
$options[] = '-L';
$options[] = $new_name;
$old_tmp = new TempFile();
$new_tmp = new TempFile();
Filesystem::writeFile($old_tmp, $old);
Filesystem::writeFile($new_tmp, $new);
list($err, $diff) = exec_manual(
'diff %Ls %s %s',
$options,
$old_tmp,
$new_tmp);
if (!$err) {
// This indicates that the two files are the same (or, possibly, the
// same modulo whitespace differences, which is why we can't do this
// check trivially before running `diff`). Build a synthetic, changeless
// diff so that we can still render the raw, unchanged file instead of
// being forced to just say "this file didn't change" since we don't have
// the content.
$entire_file = explode("\n", $old);
foreach ($entire_file as $k => $line) {
$entire_file[$k] = ' '.$line;
}
$len = count($entire_file);
$entire_file = implode("\n", $entire_file);
// TODO: If both files were identical but missing newlines, we probably
// get this wrong. Unclear if it ever matters.
// This is a bit hacky but the diff parser can handle it.
$diff = "--- {$old_name}\n".
"+++ {$new_name}\n".
"@@ -1,{$len} +1,{$len} @@\n".
$entire_file."\n";
} else {
if ($this->ignoreWhitespace) {
// Under "-bw", `diff` is inconsistent about emitting "\ No newline
// at end of file". For instance, a long file with a change in the
// middle will emit a contextless "\ No newline..." at the end if a
// newline is removed, but not if one is added. A file with a change
// at the end will emit the "old" "\ No newline..." block only, even
// if the newline was not removed. Since we're ostensibly ignoring
// whitespace changes, just drop these lines if they appear anywhere
// in the diff.
$lines = explode("\n", $diff);
foreach ($lines as $key => $line) {
if (isset($line[0]) && $line[0] == '\\') {
unset($lines[$key]);
}
}
$diff = implode("\n", $lines);
}
}
return $diff;
}
/**
* Generate an @{class:DifferentialChangeset} from two raw files. This is
* principally useful because you can feed the output to
* @{class:DifferentialChangesetParser} in order to render it.
*
* @param string Entire previous file content.
* @param string Entire current file content.
* @return @{class:DifferentialChangeset} Synthetic changeset.
* @task diff
*/
public function generateChangesetFromFileContent($old, $new) {
$diff = $this->generateRawDiffFromFileContent($old, $new);
$changes = id(new ArcanistDiffParser())->parseDiff($diff);
$diff = DifferentialDiff::newEphemeralFromRawChanges(
$changes);
return head($diff->getChangesets());
}
}

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