Better formatting for UFCS chains

libdparse

@@ -1 +1 @@
-Subproject commit 687c0ca751747ebe498c183da1a3ee3119d57932
+Subproject commit 4f3c9ed6455cc5409c2a570576f8bd994763d652

src/dfmt/ast_info.d

@@ -29,7 +29,8 @@ struct ASTInformation
     /// Sorts the arrays so that binary search will work on them
     void cleanup()
     {
-        import std.algorithm : sort;
+        import std.algorithm : sort, uniq;
+        import std.array : array;
 
         sort(doubleNewlineLocations);
         sort(spaceAfterLocations);
@@ -48,9 +49,10 @@ struct ASTInformation
         sort(constructorDestructorLocations);
         sort(staticConstructorDestructorLocations);
         sort(sharedStaticConstructorDestructorLocations);
-
         sort!((a,b) => a.endLocation < b.endLocation)
             (indentInfoSortedByEndLocation);
+        sort(ufcsHintLocations);
+        ufcsHintLocations = ufcsHintLocations.uniq().array();
     }
 
     /// Locations of end braces for struct bodies
@@ -104,6 +106,9 @@ struct ASTInformation
     /// Locations of constructor/destructor "this" tokens ?
     size_t[] constructorDestructorLocations;
 
+    /// Locations of '.' characters that might be UFCS chains.
+    size_t[] ufcsHintLocations;
+
     BraceIndentInfo[] indentInfoSortedByEndLocation;
 }
 
@@ -295,6 +300,26 @@ final class FormatVisitor : ASTVisitor
 
     override void visit(const UnaryExpression unary)
     {
+        import std.typecons : rebindable;
+
+        int chainLength;
+        auto u = rebindable(unary);
+        while (u !is null)
+        {
+            if (u.identifierOrTemplateInstance !is null
+                    && u.identifierOrTemplateInstance.templateInstance !is null)
+                chainLength++;
+            u = u.unaryExpression;
+        }
+        if (chainLength > 1)
+        {
+            u = unary;
+            while (u.unaryExpression !is null)
+            {
+                astInformation.ufcsHintLocations ~= u.dotLocation;
+                u = u.unaryExpression;
+            }
+        }
         if (unary.prefix.type == tok!"~" || unary.prefix.type == tok!"&"
                 || unary.prefix.type == tok!"*"
                 || unary.prefix.type == tok!"+" || unary.prefix.type == tok!"-")

src/dfmt/formatter.d

@@ -1229,11 +1229,14 @@ private:
             break;
         case tok!".":
             regenLineBreakHintsIfNecessary(index);
-            if (linebreakHints.canFind(index) || (linebreakHints.length == 0
+            immutable bool ufcsWrap = astInformation.ufcsHintLocations.canFindIndex(current.index);
+            if (ufcsWrap || linebreakHints.canFind(index) || (linebreakHints.length == 0
                     && currentLineLength + nextTokenLength() > config.max_line_length))
             {
                 pushWrapIndent();
                 newline();
+                if (ufcsWrap)
+                    regenLineBreakHints(index);
             }
             writeToken();
             break;
@@ -1356,7 +1359,18 @@ private:
 
     void regenLineBreakHints(immutable size_t i)
     {
-        immutable size_t j = expressionEndIndex(i);
+        import std.range : assumeSorted;
+        import std.algorithm.comparison : min;
+        import std.algorithm.searching : countUntil;
+
+        // The end of the tokens considered by the line break algorithm is
+        // either the expression end index or the next mandatory line break,
+        // whichever is first.
+        auto r = assumeSorted(astInformation.ufcsHintLocations).upperBound(tokens[i].index);
+        immutable ufcsBreakLocation = r.empty
+            ? size_t.max
+            : tokens[i .. $].countUntil!(t => t.index == r.front) + i;
+        immutable size_t j = min(expressionEndIndex(i), ufcsBreakLocation);
         // Use magical negative value for array literals and wrap indents
         immutable inLvl = (indents.topIsWrap() || indents.topIs(tok!"]")) ? -indentLevel
             : indentLevel;

tests/allman/breakOnDots.d.ref

@@ -3,7 +3,8 @@ unittest
     {
         {
             foreach (abcde, def; abcdef.map!(battlecruiser => battlecruiser[123 .. 1231231])
-                    .filter!(bravo => charlie[10] > 90000).sum())
+                    .filter!(bravo => charlie[10] > 90000)
+                    .sum())
             {
 
             }

tests/allman/ufcschain.d.ref

@@ -0,0 +1,6 @@
+void main()
+{
+    stuff[].map!(things => stuff.doThings)
+        .filter!(stuff)
+        .array();
+}

tests/otbs/breakOnDots.d.ref

@@ -2,7 +2,8 @@ unittest {
     {
         {
             foreach (abcde, def; abcdef.map!(battlecruiser => battlecruiser[123 .. 1231231])
-                    .filter!(bravo => charlie[10] > 90000).sum()) {
+                    .filter!(bravo => charlie[10] > 90000)
+                    .sum()) {
 
             }
             abcdeabcdeabcde(12341234).abcdeabcdeabcde(12341234).abcdeabcdeabcde(12341234)

tests/otbs/ufcschain.d.ref

@@ -0,0 +1,5 @@
+void main() {
+    stuff[].map!(things => stuff.doThings)
+        .filter!(stuff)
+        .array();
+}

tests/ufcschain.d

@@ -0,0 +1,4 @@
+void main()
+{
+    stuff[].map!(things => stuff.doThings).filter!(stuff).array();
+}