/// <summary>
/// This method can be called to obtain a DependsOnList for any DAX expression. This is useful when the
/// user is currently editing the DAX expression of an object, but the expression has not been saved to
/// the object.
/// </summary>
public static DependsOnList GetDependencies(IDaxDependantObject expressionObj, string dax, DAXProperty prop)
{
var dependsOn = new DependsOnList(null);
ParseExpression(dax, expressionObj, prop, dependsOn);
return(dependsOn);
}
private static void ParseExpression(string dax, IDaxDependantObject expressionObj, DAXProperty prop, DependsOnList dependsOn = null)
{
var tokens = new DAXLexer(new AntlrInputStream(dax)).GetAllTokens();
IToken lastTableRef = null;
int startTableIndex = 0;
for (var i = 0; i < tokens.Count; i++)
{
// TODO: This parsing could be used to check for invalid object references, for example to use in syntax highlighting or validation of expressions
var tok = tokens[i];
switch (tok.Type)
{
case DAXLexer.TABLE:
case DAXLexer.TABLE_OR_VARIABLE:
if (i < tokens.Count - 1 && tokens[i + 1].Type == DAXLexer.COLUMN_OR_MEASURE)
{
// Keep the token reference, as the next token should be column (fully qualified).
lastTableRef = tok;
startTableIndex = tok.StartIndex;
}
else
{
// Table referenced directly, don't save the reference for the next token.
lastTableRef = null;
}
if (Model.Tables.Contains(tok.Text.NoQ(true)))
{
if (dependsOn != null)
{
dependsOn.Add(Model.Tables[tok.Text.NoQ(true)], prop, tok.StartIndex, tok.StopIndex, true);
}
else
{
expressionObj.AddDep(Model.Tables[tok.Text.NoQ(true)], prop, tok.StartIndex, tok.StopIndex, true);
}
}
else
{
// Invalid reference (no table with that name) or possibly a variable or function ref
}
break;
case DAXLexer.COLUMN_OR_MEASURE:
// Referencing a table just before the object reference
if (lastTableRef != null)
{
var tableName = lastTableRef.Text.NoQ(true);
lastTableRef = null;
if (!Model.Tables.Contains(tableName))
{
return; // Invalid reference (no table with that name)
}
var table = Model.Tables[tableName];
// Referencing a column on a specific table
if (table.Columns.Contains(tok.Text.NoQ()))
{
if (dependsOn != null)
{
dependsOn.Add(table.Columns[tok.Text.NoQ()], prop, startTableIndex, tok.StopIndex, true);
}
else
{
expressionObj.AddDep(table.Columns[tok.Text.NoQ()], prop, startTableIndex, tok.StopIndex, true);
}
}
// Referencing a measure on a specific table
else if (table.Measures.Contains(tok.Text.NoQ()))
{
if (dependsOn != null)
{
dependsOn.Add(table.Measures[tok.Text.NoQ()], prop, startTableIndex, tok.StopIndex, true);
}
else
{
expressionObj.AddDep(table.Measures[tok.Text.NoQ()], prop, startTableIndex, tok.StopIndex, true);
}
}
}
// No table reference before the object reference
else
{
var table = (expressionObj as ITabularTableObject)?.Table;
// Referencing a column without specifying a table (assume column in same table):
if (table != null && table.Columns.Contains(tok.Text.NoQ()))
{
if (dependsOn != null)
{
dependsOn.Add(table.Columns[tok.Text.NoQ()], prop, tok.StartIndex, tok.StopIndex, false);
}
else
{
expressionObj.AddDep(table.Columns[tok.Text.NoQ()], prop, tok.StartIndex, tok.StopIndex, false);
}
}
// Referencing a measure or column without specifying a table
else
{
Measure m = null;
if (table != null && table.Measures.Contains(tok.Text.NoQ()))
{
m = table.Measures[tok.Text.NoQ()];
}
else
{
m = Model.Tables.FirstOrDefault(t => t.Measures.Contains(tok.Text.NoQ()))?.Measures[tok.Text.NoQ()];
}
if (m != null)
{
if (dependsOn != null)
{
dependsOn.Add(m, prop, tok.StartIndex, tok.StopIndex, false);
}
else
{
expressionObj.AddDep(m, prop, tok.StartIndex, tok.StopIndex, false);
}
}
}
}
break;
default:
lastTableRef = null;
break;
}
}
}
