Pascal Indent vs. Manual Styling: When to Use Each Approach

Pascal Indent Tips: Fixing Common Indentation MistakesGood indentation improves readability, reduces bugs, and makes maintenance simpler. Pascal — whether classic Turbo Pascal, Free Pascal (FPC), or Delphi Object Pascal — has clear block structures (begin/end, if/then/else, case, loops, procedures/functions) that benefit from consistent indentation. This article presents practical tips to fix common indentation mistakes, plus configuration and workflow suggestions for using pascalindent and other tools.

Why indentation matters in Pascal

• Visual structure — Indentation reveals the program’s logical nesting: which statements belong to which blocks.
• Error spotting — Mismatched begin/end pairs and misplaced else or end statements become easier to spot.
• Team consistency — A shared style reduces friction in code reviews and merges.

Common indentation mistakes

1. Misaligned begin/end blocks

   • Problem: begin and end at different indentation levels, hiding block boundaries.
   • Symptom: Hard-to-follow nested logic, especially with multiple nested loops or conditionals.

2. Incorrect else alignment

   • Problem: else aligned with the inner statement instead of the matching if.
   • Symptom: Confusing which if the else corresponds to, increasing risk of logic errors.

3. Inconsistent indentation size

   • Problem: Mixing tabs and spaces or varying number of spaces per level.
   • Symptom: File looks different in different editors; merges produce noisy diffs.

4. Misplaced statements after end; missing semicolons

   • Problem: Statements following an end may appear at incorrect indentation, obscuring that a new block started. Missing semicolons can change intended grouping.
   • Symptom: Compiler errors or surprising control-flow.

5. Long compound statements on one line

   • Problem: Combining several clauses or nested constructs on a single line.
   • Symptom: Reduced readability and increased chance of missing an else or end.

Tools: pascalindent and editor integrations

• pascalindent is a widely used command-line formatter for Pascal code. It supports many options to control indentation style, spacing, and alignment. Other formatters or IDEs (Delphi’s code formatter, Editor plugins) can also help.
• Integrate pascalindent into your editor (VS Code, Emacs, Vim) or as a git pre-commit hook to enforce consistent style automatically.

Basic usage example:

pascalindent -l -w -i4 input.pas -o output.pas 

(Use your system’s pascalindent documentation for exact flags.)

Configuration recommendations

• Indent size: 4 spaces is a common default that balances compactness and clarity. Avoid mixing tabs and spaces.
• Use spaces over tabs by default; if your team prefers tabs, set a single tab per level.
• Keep begin and end aligned vertically. Place end on its own line unless you follow a disciplined compact style.
• Align else with the matching if, not with the inner statement.

Example preferred style:

if Condition then begin     DoSomething;     if SubCondition then     begin         DoSub;     end     else     begin         HandleSub;     end; end else begin     HandleOther; end; 

pascalindent options to watch

• Indentation width (often -i or similar flag) — set to 4 for consistency.
• Align else and case labels options — ensure else aligns with if.
• Keep/expand one-line blocks — expand single-line blocks to multiple lines when nested, to avoid hidden structure.
• Back up original files or use output redirection to verify changes before overwriting.

Fixing specific mistakes — examples and fixes

1. Misaligned begin/end

   • Before:

     
     if A then begin  DoA;  if B then    begin      DoB;    end; end; 

   • After pascalindent / manual fix:

     
     if A then begin  DoA;  if B then  begin      DoB;  end; end; 

2. Else alignment issue

   • Before:

     
     if Flag then if Sub then  DoX else  DoY; 

     (This appears to pair else with inner if, which might be intended or not.)

   • Recommended explicit style:

     
     if Flag then begin  if Sub then      DoX  else      DoY; end; 

3. Mixed tabs and spaces

   • Fix: convert all tabs to spaces (or vice versa) with your editor or pascalindent setting; commit a single reformatting change to minimize noise in history.

4. One-line compound statements

   • Before:

     
     for I := 1 to N do if Arr[I] = X then DoIt; 

   • After:

     
     for I := 1 to N do begin  if Arr[I] = X then      DoIt; end; 

Workflow tips

• Add pascalindent to your build or CI pipeline to automatically fail on poorly formatted code or to reformat during CI runs.
• Use a pre-commit hook that runs pascalindent and prevents commits with mixed indentation.
• Keep a style guide in your repository with examples of allowed/forbidden patterns.
• When rebasing or applying large formatting changes, separate style-only commits from logic changes to keep history clear.

Debugging tricky cases

• Deeply nested logic: consider extracting nested blocks into procedures/functions; this reduces indentation depth and increases clarity.
• Conditional chains (if/else if/else): use explicit begin/end blocks for multi-statement branches.
• Case statements: align case labels at the same level; use begin/end within each case when needed.

Example:

case Choice of     1:     begin         HandleOne;     end;     2:     begin         HandleTwo;     end; else     HandleDefault; end; 

Summary checklist before committing code

• Indentation consistent (spaces or tabs), typically 4 spaces per level.
• begin/end and else properly aligned.
• No mixed tabs and spaces.
• Multi-statement branches use begin/end.
• pascalindent or equivalent runs cleanly on the file.

Keeping Pascal code well-indented is mostly about consistent rules and automation. Use pascalindent, integrate it into your editor/CI, and apply the simple stylistic rules above to prevent and fix the most common indentation mistakes.