Forum Discussion
Error handling is primary source is absent
hi,
I would like to build a query that normally pulls the data from "C:\pathA\fileA" but if fileA is not out there, it pulls from "C:\pathB\fileB". I've tried the following but nothing works... It throws a DataSource.Error: Could not find file "C:\pathA\fileA".
Source = try Csv.Document(File.Contents("C:\pathA\fileA.csv"),[Delimiter=",", Columns=36, Encoding=1252, QuoteStyle=QuoteStyle.None]) otherwise Csv.Document(File.Contents("C:\pathB\fileB.csv"),[Delimiter=",", Columns=36, Encoding=1252, QuoteStyle=QuoteStyle.None]) Source = Csv.Document(File.Contents("C:\pathA\fileA.csv"),[Delimiter=",", Columns=36, Encoding=1252, QuoteStyle=QuoteStyle.None]),
AlternativeOutput = Csv.Document(File.Contents("C:\pathB\fileB.csv"),[Delimiter=",", Columns=36, Encoding=1252, QuoteStyle=QuoteStyle.None]),
TestForError = try Source,
Output = if TestForError[HasError] then AlternativeOutput else #"Promoted Headers", Source = Csv.Document(File.Contents("C:\pathA\fileA.csv"),[Delimiter=",", Columns=36, Encoding=1252, QuoteStyle=QuoteStyle.None]),
TestForError = try Source,
Output = if TestForError[HasError] then Csv.Document(File.Contents("C:\pathB\fileB.csv"),[Delimiter=",", Columns=36, Encoding=1252, QuoteStyle=QuoteStyle.None]),
else #"Promoted Headers",
your help would be highly appreciated!
Artur
Hi Artur,
Your issue is with File.Contents: It gets an error trying to access the file but transforms this error into a binary anyway. So, when try is executed it gets a value but without errors, since the error is inside this value.
Since error are transferable, I'm not sure how this happens.
It is -- for me -- a bug of the pqengine evaluation system.
Aaaaanyway,
Try using file.contents alone, something like:Source = try (try File.Contents(filestring1))[Value]{0},Source_final = if Source[HasError] then File.Contents(filestring2) else File.Contents(filestring1)Nah, I actually tested this. It won't work since the error is still inside the binary. It happens on accessing it. This will work:Source = try Binary.Length((try File.Contents(filestring1))[Value])
Source_final = if Source[HasError] then File.Contents(filestring2) else File.Contents(filestring1)
And then apply the csv transformations
Edit2: You could also simplify step1 as :
try Binary.Length(File.Contents(filestring1))
4 Replies
This should work:
let Source = Csv.Document(Text.FromBinary(File.Contents("C:\pathA\fileA.csv"), TextEncoding.Windows),[Delimiter=",", Columns=36, QuoteStyle=QuoteStyle.None]), #"Alternative Source" = Csv.Document(Text.FromBinary(File.Contents("C:\pathB\fileB.csv"), TextEncoding.Windows),[Delimiter=",", Columns=36, QuoteStyle=QuoteStyle.None]), Output = try Source otherwise #"Alternative Source" in OutputHi Artur,
Your issue is with File.Contents: It gets an error trying to access the file but transforms this error into a binary anyway. So, when try is executed it gets a value but without errors, since the error is inside this value.
Since error are transferable, I'm not sure how this happens.
It is -- for me -- a bug of the pqengine evaluation system.
Aaaaanyway,
Try using file.contents alone, something like:Source = try (try File.Contents(filestring1))[Value]{0},Source_final = if Source[HasError] then File.Contents(filestring2) else File.Contents(filestring1)Nah, I actually tested this. It won't work since the error is still inside the binary. It happens on accessing it. This will work:Source = try Binary.Length((try File.Contents(filestring1))[Value])
Source_final = if Source[HasError] then File.Contents(filestring2) else File.Contents(filestring1)
And then apply the csv transformations
Edit2: You could also simplify step1 as :
try Binary.Length(File.Contents(filestring1))
