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PhabricatorDifferenceEngine.php
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Mon, May 12, 21:21

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 $oldName;
private $newName;
private $normalize;
/* -( Configuring the Engine )--------------------------------------------- */
/**
* Set the name to identify the old file with. Primarily cosmetic.
*
* @param string Old file name.
* @return this
* @task config
*/
public function setOldName($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 $this;
}
public function setNormalize($normalize) {
$this->normalize = $normalize;
return $this;
}
public function getNormalize() {
return $this->normalize;
}
/* -( Generating Diffs )--------------------------------------------------- */
/**
* Generate a raw diff from two raw files. This is a lower-level API than
* @{method:generateChangesetFromFileContent}, but may be useful if you need
* to use a custom parser configuration, as with Diffusion.
*
* @param string Entire previous file content.
* @param string Entire current file content.
* @return string Raw diff between the two files.
* @task diff
*/
public function generateRawDiffFromFileContent($old, $new) {
$options = array();
// 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;
$normalize = $this->getNormalize();
if ($normalize) {
$old = $this->normalizeFile($old);
$new = $this->normalizeFile($new);
}
$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. 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";
}
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());
}
private function normalizeFile($corpus) {
// We can freely apply any other transformations we want to here: we have
// no constraints on what we need to preserve. If we normalize every line
// to "cat", the diff will still work, the alignment of the "-" / "+"
// lines will just be very hard to read.
// In general, we'll make the diff better if we normalize two lines that
// humans think are the same.
// We'll make the diff worse if we normalize two lines that humans think
// are different.
// Strip all whitespace present anywhere in the diff, since humans never
// consider whitespace changes to alter the line into a "different line"
// even when they're semantic (e.g., in a string constant). This covers
// indentation changes, trailing whitepspace, and formatting changes
// like "+/-".
$corpus = preg_replace('/[ \t]/', '', $corpus);
return $corpus;
}
}

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