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Download: never leave the target file behind after a failure #103

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2 changes: 2 additions & 0 deletions doc/download.xml
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Original file line number Diff line number Diff line change
Expand Up @@ -68,6 +68,8 @@ The following components are supported.
that is a local filename,
and the function writes the downloaded contents to this file;
the returned record does not have a <C>result</C> component in this case.
<P/>
If the download fails then this file is not left behind.
</Item>
<Mark><C>verifyCert</C></Mark>
<Item>
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26 changes: 22 additions & 4 deletions lib/download.gi
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Expand Up @@ -125,10 +125,16 @@ Add( Download_Methods, rec(
res:= ValueGlobal( "SingleHTTPRequest" )( domain, port, "GET", uri,
rec( Host:= authority ), false, false );
fi;
if res.statuscode = 0 then
return rec( success:= false,
error:= res.status );
elif res.statuscode >= 400 then
if res.statuscode = 0 or res.statuscode >= 400 then
# 'SingleHTTPRequest' has already written the response body, for example
# an error page, to the target file; remove it.
if IsBound( opt.target ) and IsString( opt.target ) and
IsExistingFile( opt.target ) then
RemoveFile( opt.target );
fi;
if res.statuscode = 0 then
return rec( success:= false, error:= res.status );
fi;
return rec( success:= false,
error:= Concatenation( "HTTP error code ",
String( res.statuscode ) ) );
Expand Down Expand Up @@ -219,6 +225,11 @@ Add( Download_Methods, rec(
code:= Process( DirectoryCurrent(), exec, InputTextNone(), outstream, args );
CloseStream( outstream );
if code <> 0 then
# curl may have created the target file; remove it, as wget's method does
if IsBound( opt.target ) and IsString( opt.target ) and
IsExistingFile( opt.target ) then
RemoveFile( opt.target );
fi;
return rec( success:= false,
error:= Concatenation( "Process returned ", String( code ) ) );
elif not ( IsBound( opt.target ) and IsString( opt.target ) ) then
Expand Down Expand Up @@ -270,6 +281,13 @@ InstallMethod( Download,
if res.success = true then
return res;
fi;
# A failed method may have left a partial or bogus target file behind.
# Remove it here, so that the guarantee holds for every method,
# including ones added to 'Download_Methods' from outside.
if IsBound( opt.target ) and IsString( opt.target ) and
IsExistingFile( opt.target ) then
RemoveFile( opt.target );
fi;
Info( InfoUtils, 2, "Download method ", r.name, " failed with\n",
"#I ", res.error );
Add( errors, Concatenation( r.name, ": ", res.error ) );
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20 changes: 20 additions & 0 deletions tst/download.tst
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Expand Up @@ -139,6 +139,26 @@ gap> res1:= Download( url, rec( maxTime:= 5 ) );;
gap> res1.success = true;
true

## A failed download must not leave the target file behind,
## whichever method was used.
gap> file:= Filename( DirectoryTemporary(), "target" );;
gap> for r in meths do
> res1:= r.download( Concatenation( baseurl, "/missing" ),
> rec( target:= file ) );
> if res1.success = true then
> Print( "unexpected success for ", r.name, "\n" );
> elif IsExistingFile( file ) then
> Print( "leftover target file after ", r.name, "\n" );
> RemoveFile( file );
> fi;
> od;
gap> res1:= Download( Concatenation( baseurl, "/missing" ),
> rec( target:= file ) );;
gap> res1.success = false;
true
gap> IsExistingFile( file );
false

## test errors and redirects
gap> res1:= Download( Concatenation( baseurl, "/missing" ) );;
gap> res1.success = false;
Expand Down